The sun is apparently the most magnificent and splendid orb in the heavens. And the most obvious phenomena attending it, are its light, its heat, and its daily rising and setting; but although the sun appears extremely bright and splendid to the naked eye, yet he is frequently observed even through a telescope of very moderate powers, to have dark spots on his disk. These were first discovered in 1611 : and the honour of the discovery was disputed between Galileo and Scheiner a German jesuit of Ingolstadt.

There is a great variety in the magnitude of these spots. The difference is chiefly in superficial extent of length and breadth ; their depth or thickness is very small; some have been computed to be so large, as to be capable of covering the continents of Asia, and Africa, and even of the globe itself. The diameter of a spot, when near the middle of the disk is measured by comparing the time it takes in passing of a hair, laid across the telescope, with the time it takes the whole disk to pass over the same hair; it may also be measured by a micrometer. By either of these methods, we may judge how many times the diameter of the spot is contained in the diameter of the sun.

It is observed that these spots are subject to increase and diminution of their magnitude, that they are of various shapes, most of them having a deep black nucleus surrounded by a dusky cloud, whereof the inner parts near the black are a little brighter than the out-skirts. They frequently change their shapes in the manner of our clouds, though not often so suddenly: thus what is of a certain figure to-day, tomorrow, or perhaps in a few hours shall be of a different one ; one spot is sometimes broken into two or three, and sometimes two or three spots shall coalesce, and be united in one. The number of spots is very uncertain, sometimes there are a great many, sometimes very few; and sometimes none at all.

It is evident from the various appearances, that the spots are not endowed with any permanency, nor are they uniform in shape, number magnitude, or duration. Hevelius observed one that arose and vanished in 16 or 17 hours; and no one has been observed to continue longer than 70 days; in general those spots which are gradually formed, are gradually dissolved; and those which appear suddenly, are suddenly dissipated; it has been observed that when a spot disappears, the particular place which it occupied becomes brighter, on the other band those parts called faculae frequently turn to spots.

The sun when free from spots, appears equally luminous to the eye, or through coloured glasses. But through a telescope, the middle of the disk appears brighter than the out-skirts, the light darting more directly to us from the middle than the other parts, and the faculae appear more distinctly near the sides.

The spots are not confined to one part of the sun’s disk; though we have not heard of any being observed about his polar regions. They described different courses over the sun’s disk, sometimes they travel in straight lines, sometimes in curves; sometimes descending from the northern to the southern part of the disk, sometimes ascending from the southern to the northern, &c. Besides these spots there are others which sometimes appear very round and black, travelling over the sun’s disk in a few hours, and are totally unlike the others. These proceed from the interposition of the planets, Mercury, and Venus, between the earth and the sun. Excepting these two kinds of spots, nothing is discoverable on the surface of the sun, but he appears like an immense ocean of light.

Mr. Huygene supposed the sun to be a liquid globe, which the equal distribution of its rays, he thought was an argument for. The small inequalities upon it discovered by means of the telescope, and which has made some imagine they saw huge mountains of fire, he considered as entirely owing to the trembling motions of the vapours of our atmosphere; and that it was likewise the cause of the twinkling of the stars; and indeed it is not much to be doubted but that our vision is abundantly, more affected by the medium of our own atmosphere than we are aware of For instance, should we deviate ever so little from the old established hypothesis, that light travels in straight lines, and should it hereafter be discovered, that the motion of light, like all other motion, is elliptical, it would very materially affect our calculations of the distances, magnitudes, and appearances of the celestial bodies.

When the moon passes between the earth and the sun, so as to intercept his rays, he is said to be eclipsed. This happens only at the time of new moon, because it is then only she passes between the sun and the earth. Yet the sun is not eclipsed at every new moon, because the moon more frequently declines from a straight line between the earth and the sun, either to the north, or the south. And this is also the case when the moon passes at the opposite conjunction, when she passes to the northward or southward of the earth’s shadows.

No solar eclipse can be universal, the moon being too small to overshadow the whole earth. Consequently the eclipses of the sun do not appear the same in all places, but are total in one, and partial in another. In most solar eclipses the moon is covered with a faint dawning light, which appears owing to the reflection of the light from the illuminated parts of the earth. In total eclipses, the moon’s edge is seen surrounded by a pale circle of light, which is at least a probable indication. of a lunar atmosphere.

When the earth is interposed between the moon and the sun in a direct line, so as to intercept his rays upon the moon, then the moon is eclipsed. And this is only at the time of the full moon. In the midst of a lunar eclipse the moon is observed to have a faint light, which is supposed to be reflected by the’ atmosphere of the earth, and that to the shadow of this it is owing, that she grows paler and dimmer before she enters into the shadow of the earth.

The interior conjunction of the planets, Mercury, and Venus, when passing over the sun’s disk, are not called eclipses, but transits.

The greatest diameter of the sun as seen from the earth is 32’ 36’, or 883,217 miles. It is stated from observations to revolve on its own axis in 25h. 15’ 16”, and is computed to be 1,380,000 times larger than the earth. It has been calculated to be 97,000,000 of miles distant from our earth.

2. Mercury to our observation at least, is the nearest planet t. the sun; this planet when viewed through a telescope magnifying about 200 or 300 times, appears equally luminous throughout his whole surface, without the least spot. He exhibits the same phases with the moon, being sometimes horned, sometimes gibbous, and sometimes shining with a full face, though not entirely full, because his enlightened side is never turned directly towards us, but at all times perfectly well defined, without any ragged edge and perfectly bright.

This planet performs its entire revolution in its orbit, in 87 days, 23 hours, and 15 1/4 minutes, which of course is the length of its year. Its distance from the sun is computed to be 27,000,000 of miles, or as have computed it to be 1/4 the distance of the earth. Its greatest apparent diameter as seen. from the earth 11”, or 3222 miles. ‘Its diurnal rotation is unknown, it not being possible from appearance on his disk, to come at a knowledge of his rotary motion. - The inclination of his orbit to the ecliptic, is 70; its bulk is (thpnted to be of that of our earth, and its proportion of density 2-1, and its light 6-I.

3.Venus is next to Mercury, and the second interior planet it is rarely seen to shine with a full face, but has phases and changes like those of the moon, her illuminated hemisphere being constantly turned towards the sun. This planet is what is termed the morning and evening star, as she is situated in different parts of her orbit.

Dr. Herschel has published in the philosophical transactions for 1793, a long series of observations on this planet, whence he concludes, that the planet revolves about its axis, but that the period, and position of the axis are uncertain, that it has a very considerable atmosphere; that it exhibits inequalities of surface, though he could not discover much of them; owing probably to the density of its atmosphere; and that this planet instead of being smaller, is somewhat larger than the earth; though former astronomers have computed its diameter at 7687 miles, which is 275 miles less than the diameter of the earth, or its bulk of the’ earth; and its diurnal rotation to be 23h. 22’. Its mean distance from the sun, is computed to be 68,000,000 of miles.

The earth as a planet, offers itself next to our contemplation, as being situated next in order in the solar system. But as it involves phenomena, and considerations abundantly more numerous and interesting than the surrounding orbs, we shall first take a brief survey of those celestial bodies, which occupy the remoter regions of space, and first of the exterior planets, Mars, Jupiter, Saturn, and Herschel.

4.Mars is the next planet; and is called an exterior planet, because it describes an orbit without the orbit of the earth. He is of a red, fiery colour, and gives a much duller light than Venus, though he sometimes equals her in size. He is not subject to the same limitations as Venus or Mercury, but appears sometimes very near the sun, and sometimes at a great distance from him. Sometimes rising when the sun sets, or setting when he rises. Mars appears gibbous when near his quadratures with the sun.

Much larger and more remarkable spots have been perceived on the disk of Mars, than on that of any other primary planet. By very accurate observations, Herschel has determined the proportion between the polar and equatorial diameters, and the length of the day of this planet. He has also given some plausible conjectures on its and atmosphere; the latter it is now satisfactorily ascertained to have, though not to so great an extent, as conjectures on former observations led astronomers to imagine.

The mean distance of Mars from the sun is computed to be 144.000,000 of miles, its diameter 1189 miles. Its diurnal rotation, 24h, 39’ 22”, the inclination of its orbit to the elliptic, 10 51’. Its proportion of solar light, 43. Its bulk in proportion to the earth 7/10 And its proportion of density

5. Jupiter is the next exterior planet in the solar system., He has the same general appearance with Mars, only the belts on his surface are much larger, and more permanent. The number is very variable, sometimes being only one, at other times no fewer than eight may be perceived. They are generally parallel to one another, but not always so; and their breadth is likewise variable, one belt having been observed to grow narrower, while another in its neighbourhood has increased in breadth, as if the one had flowed into the other.

The time of their continuance is also uncertain. sometimes remaining unchanged for three months together, at others, new belts have been formed in an hour or two. In some of these belts large black spots have appeared, which moved briskly over the disk from east to west, and returned in a short time, to the same place; from whence the rotation of this planet abut its axis has been determined

The figure of Jupiter is evidently an oblate spheroid, the longest diameter of his disk being to that of the shortest as 13 to 12. Ills rotation is from west to east like that of the sun, and the plane of his equator is very nearly coincident with that of his orbit ; so that there can be very little difference of seasons in that planet. His rotation has been observed to be quicker in his aphelion than his perihelion.

The most remarkable circumstances attending this planet, is his having four moons or satellites, which constantly revolve round him at different distances. These are all supposed to remove in ellipses, though the eccentricities of all of them are too small to be measured, excepting that of the fourth, and even this amounts to no more than 0,007 of its mean distance from the primary.

The periodic times and distances of these satellites, in semi-diameters of Jupiter, and in English miles, the angles under which their orbits appear, as seen from the earth, at its mean distance from Jupiter, taken from the latest and most exact observations, are ‘as follows.

No.	Perdiodic Times.	Distances		Angle of Orb.
	D h ‘ “	Semi Diam.	Miles	‘ “
1	1..18..27..34	5 2/3	266,000	3..35
2	3..13..13..42	9 1/56	423,000	6..14
3	7.. 3..42.. 36	14 5/16	676,000	7..58
4	16..16..32..9	25 3/16	1,189,000	17..30

6. Saturn sometimes appears at a vast distance from the sun shines with a very faint light; and his motion is so slow among the fixed stars that unless carefully observed, he will scarcely be thought to move at all When viewed through a good telescope, he makes a more remarkable appearance than any of the other planets. Galileo first discovered his uncommon shape, and from his discoveries and those of other astronomers, it appears that this planet is surrounded by a broad ring, the edge of which reflect little or none of the sun’s light to us; but the planes of the ring reflect the light in the same as the planet itself does: the diameter of the ring is about the diameter of the body of the planet. The ring is detached from the body of the planet in such a manner, that the distance between the innermost ‘part of the ring and its body, is equal to its breadth.

Dr. Hershel has found in the course of observation, that the ring is double, or that there are two concentric rings; also that it has a motion of rotation in its own plane, its axis of motion being the same with that of Saturn himself, and its periodical time 10h 32’ 15”. 4 but he thinks it probable, that the concentric rings may not revolve in the same period. Their dimensions and the space between them, he states in the following proportions to each other.

Miles.

Inner diameter of the small ring, .. 146,345

Outward diameter of do. 184,393

Inner diameter of the large ring, 190,248

Outside diameter of do. 204,883

Breadth of the inner do. 20,000

Breadth of the outer do. 7,200

Breadth of the vacant space 2,839

Dr. Herschel concludes from his observations on the ring, that its structure is such, as to alLow it to remain permanently in its present state; nor does he think it at all probable, that the ring is of that changeable nature which some have imagined.

The same excellent astronomer has concluded from a series of observations on the belts of Saturn, that he revolves on his axis in 10h. 16' 0”.4, that be has a dense atmosphere, and that his polar diameter is to his equatorial as 10 to 11.

Saturn has, besides his ring, seven secondary planets or satellites revolving round him. One of them, which till lately was reckoned the fourth in order from Saturn, was discovered by Huygens, in 1655, and by means of a telescope of 100 feet long; and the others; viz. the 1st, 3d 4th., and 5th. at different times by Cassini, between 1671 and and 1684, by the help of glasses of 100 and 136 feet. The 6tband 7th have been lately discovered by Herschel, with his 40 feet reflecting telescope in 1787 and 1788. These he has called the 6th and 7th satellites, though they are nearer to Saturn than the other 5, that the names may not be mistaken with regard to former observations of them.

The periodical revolutions and distances of these satellites ex. pressed in semi-diameters of that planet, and in English miles, are as follows.

No.	Periodical Times	Distances in		Angle of Orbit
	D h ‘ “	Semi Diam.	Miles	‘ “
1	1 21 13 27	4 3/8	170,000	1 27
2	2 17 41 22	5	217,000	1 52
3	4 12 25 12	8	303,000	2 36
4	15 22 41 13	18	704,000	6 18
5	72 7 48 0	54	2,050,000	1 14
6	1 8 53 9	3 5/9	135,000	1 14
7	0 22 40 46	2 5/6	107,000	0 57

The 4 first described ellipses like those of the ring, are in the same plane: their inclination to the orbit, is from 300 to 31. The 5th describes an orbit inclined from 17 to 18 to the orbit of Saturn, his plane lying between the ecliptic and those of the other satellites. Dr. Herschel observes that the 5th satellite turns round its axis once, exactly in the time in which it revolves round the planet Saturn. In this respect it resembles our moon, which does the same thing.

7. The Georgium Sidus, or Herschel, being more remote than Saturn, is also less known. Its apparent magnitude is so small, that it can seldom be seen by the naked eye, and even when viewed by means of the telescope, it appears only a few seconds in diameter. This planet was discovered by Dr. Herschel, in 1781; and in 1787 he likewise discovered two satellites that revolve round it. They are probably not less than Jupiter’s moons, and their orbits are nearly perpendicular to the ecliptic. This is a circumstance in which they differ from the attendants of all the other planets.

Their periods of revolution and angular distances from their primary, are as follows.

No.	Periods.	Distance
	D h ‘ “	‘ “
1	8 17 1 19	0 33
2	13 11 5 1 1/3	0 44 2/9

8. Comets are another class of planets appertaining to our system, and which exhibit appearances vastly different from any of the other planets. The nucleus or star, seems much dimmer; they are to appearance surrounded with atmospheres of a prodigious size, often rising ten times higher than the nucleus, and often likewise exhibit different phases, like the moon.

What is called the head of a comet, or the round part, appears to be a solid globe, and is called the nucleus, which is easily distinguished from the atmosphere of hairy appearance.

Comets are peculiarly distinguished by a blaze or tail, also by the eccentricity of their motion. Sometimes the tail only has been seen at ‘the head has been hid under the horizon, then it is termed a beam. There appears to be a relative degree of conformity peculiar shape of the atmosphere of comets, the velocity with which they move, and the extreme ellipsis in which they traverse. None of the celestial bodies have given rise to a greater degree of speculation and conjecture than the comets. Their strange appearance has in all ages been a matter of terror to the vulgar, who uniformly looked upon them as bad omens, or forerunners of war, pestilence, &c. Others less superstitious, have supposed them to be meteors formed in the upper regions of the air. After much speculation and conjecture among astronomers, Tycho Brahe restored them to their true rank in the creation, and Sir Isaac Newton at length discovered their true motion, from the observations he made on the great comet which appeared in 1680 This comet appeared to descend almost perpendicular towards the sun with a prodigious velocity; ascending again with a motion retarded as much as it had been before accelerated. It was seen in the morning by a great number of astronomers in different parts of Europe from the 4th to the 25th of November, in its way towards the sun, and in the evening, from the 12th of December to the 9th of March following. The many exact observations made on this comet, enabled Sir Isaac Newton to deter-mine, that they are a kind of planets, which move in very eccentric ellipses and this opinion is now considered as an established truth. Although the orbits of all comets are very eccentric ellipses, yet there ‘are very great differences among them. Excepting the orbit of Mercury there are no great differences among those of the planets, either as to their eccentricity, or the inclination of their planes; but the planes of some comets are almost perpendicular to others, and. some of their ellipses are much wider than others. The narrowest. ellipsis of any comet hitherto observed, was that of 1680. There is also a much greater inequality in the motion of the comets, than in the planets; the velocity of the former being incomparably greater in their perihelion than in their aphelion; but the planets are but little accelerated. Hence it is apparent, that the degree of acceleration of any orb, will be in a ratio proportionate to the degree of the ellipsis of its orbit ; for it is evident from all observation, that a body is retarded in its aphelion, in a degree corresponding to its acceleration in its perihelion distance.

It is now universally allowed that comets are opaque bodies, enlightened by the sun. Sir Isaac Newton observes that if a comet be observed, in two parts of its orbit at equal distances from the earth, but at unequal distances from the sun, it always shines brightest in that part which is nearest to the sun.

Comets are of very different magnitudes, which may be observed from their apparent diameters and brightness.

The extraordinary atmospheres, or tails of comets, have given rise to various conjectures, though it is allowed by all, that they depend on the sun some way or other, as they are always directed towards him in one undeviating position; but by what means this is effected is a subject of dispute among philosophers.

The analogy discovered by that indefatigable astronomer, Kepler between the periodical times of the planets, and their distances from the sun, takes place also in the comets. In consequence this, the mean distance of a comet from the sun, may be found by comparing its period with the time of the revolution round the sun. Thus the period of the comet which appeared in 1531, ,IeOI, I68 and 1759 being about 76 years, and whose regular return will be about the year 1835, its mean distance may be found by the following proportion. As I, the square of one year, the earth’s periodical time, is to 5776, the square of 76, the comet’s periodical time, so is 1,000,000, the cube of 100, the earth’s mean distance from the sun, to 5,77,000,000, the cube of the comet’s mean distance. The root of this last number

1794, the mean distance itself in such parts as the mean distance of the earth from the sun contains 100. If the perihelion distance of the comet 58, be taken from 3588, double the mean distance, we shall have the aphelion distance 3530, of such parts as the distance of the earth contains 100, which is a little more than 35 times the distance of the earth from the sun. By a like method, the aphelion distance of the comet of 1680, comes out 138 times the mean distance of the earth from the sun, supposing its period 575 years ; so that this comet in its aphelion goes more than 14 times the distance from the sun that Saturn does. Euler computes the orbit from three of Flamstead’s observations, taken nearly together, compared with a fourth, taken at some distance from the other three, and from thence concludes the.-period to be a little more than 170 years.

9.The next celestial objects which present themselves in succession to our notice, are those innumerable orbs, which we term fixed stars: they are termed fixed, because they appear not to vary their situations in the heavens, to a spectator on the earth. Astronomers have supposed them to be so many suns, each the centre of a system of habitable worlds, similar to our solar system. The strongest argument for this, is, that the stars cannot be magnified, even by the most powerful telescope, on account of their immense distance; whence it is concluded, that they shine by their own light, and are therefore so many suns; each of which we may suppose is of equal if not superior magnitude to our own. They are situated at vastly different distances from us, as is indicated by their different magnitudes; and this supposition is necessary, to prevent any interference of the orbits of the planets, and thus there may be as great a distance between a ___ of the first magnitude and one of the second, apparently close to it, as between our globe and the fixed stars themselves.

The fixed stars, instead of being magnified by the best glasses, are ___ diminished in size, on account, as is thought, that the telescope takes off that twinkling appearance which they exhibit to the naked eye., or more probably, that the rays being very much compounded in consequence of their immense passage, the superfluous rays are excluded by the instrument; and this is inferable from the fact, that the number of stars is prodigiously increased by the telescope, 70 stars having been counted in the single constellation Pleiades, and fewer than 2000 in that of Orion.

The late great discoveries and improvements of the celebrated Herschel have thrown new light on this subject, and shown the number of stars to be exceedingly beyond the discoveries, and even the apprehensions of the ancients. This able astronomer has shown that many which appear single to the naked eye, or through ordinary glasses, do in fact consist of two or more stars; and that the galaxy or milky way, owes its light entirely to multitudes of small stars, so close together, that the naked eye, or even ordinary telescopes cannot distinguish them.

The nebulae, or small whitish specks, discoverable by means of the telescope, in various parts of the heavens, are owing to the same cause. Former astronomers could only reckon 103 of these nebulous patches, but Herschel has discovered upwards of 1250. He has also discovered a species of them which he calls planetary nebulae, on account of their peculiar brightness, and their shining with a well defined disk.

In the philosophical transactions for 1783, Mr. Mitchell, in proposing a method to determine the distance, magnitude, &c. of the fixed stars, by the dimmution of the velocity of their light, should any such thing be discovered, supposes, that by far the greater par, if not all of them, are systems of stars, so near to each other, as probably to be liable to be affected sensibly by mutual gravitation; and that it is therefore not unlikely that the periods of the revolutions of some of these about their primaries, the smaller ones being upon this hypothesis to be considered as satellites to the other,) may at some time or other be discovered. Dr. Herschel, improving upon Mitchell’s idea, of the fixed stars being collected into groups, and assisted by his own observations, aided by his extraordinary telescopic powers, has suggested a theory concerning the construction of the universe, entirely novel and singular. The opinion had long prevailed among astronomers, that our sun, besides occupying the center of the system which properly belongs to him, occupied also the center of the universe; but Dr. Herschel is of a different opinion; we shall extract some of the doctor’s observations on this interesting subject.

Hitherto (says the Dr.) the siderial heavens have, not inadequately for the purpose designed, been represented by the concave surface of a sphere, in the centre of which the eye of the observer might be supposed to be placed. It is true, the various magnitudes of the fixed stars even then, plainly suggested to us, and would have better suited, the idea of an expanded firmament of three dimensions; but the observations upon which I am now going to enter, still farther illustrate and enforce the necessity of considering the heavens in this point of view. In future, therefore, we shall look upon these regions, into which we may now penetrate by means of the improved telescopes, as a naturalist regards a rich extent of ground or chain of mountains, containing strata variously inclined and directed, as well as consisting of very different materials. A surface of a globe, or a map, therefore, will but ill delineate the interior parts of the heavens.”

The doctor’s observations, on which this theory is founded, were made with a Newtonian reflector of 20 feet focal length, and an aperture of 18 inches. With this powerful telescope, he first began to survey the Via Lactea, and found that it completely resolved the whitish appearance into stars, which the telescopes he formerly used, had not light enough to do. The portion he first observed, was about the hand and club of Orion; in which he found, an astonishing multitude of stars, the number of which he endeavoured to estimate, by counting many fields, (or apparent spaces of the heavens, which he could see at once through his telescope,) and computing from a medium of these, how many might be contained in a given portion of the milky way. In the most vacant place to be met with in that neighbourhood, he found 63 stars: other six fields, contained 110, 66, 70, 90, 70, and 74 stars, a medium of all which gave 79 for the number of stars to each field.—Thus he found that by allowing 15’ for the diameter of his field of view, a belt of 15 long, and 2 broad, which lie had often seen pass before his telescope, in an hour’s time, could not contain less than 50,000 stars, large enough to be distinctly numbered besides which, he suspected twice as many more, which could be seen only now and then, by faint glimpses, for want of sufficient light.

The doctor’s success thus far, soon induced him to direct his attention to the nebulous parts of the heavens, of which an accurate list was published in the Connoissance de Temps for 1 783 and 1784. Most of these yielded to a Newtonian reflector of 20 feet focal distance, and 12 inches aperture, which plainly discovered them to be composed of stars, or at least to contain stars, and to show every other indication of consisting of them entirely.

“The nebulae (says he) are arranged into strata, and run on to a great length; and some of them I have been able to pursue and to guess pretty well at their form and direction. It is probable enough, that they may surround the whole starry sphere of the heavens, not unlike the milky way, which undoubtedly it nothing but a stratum of fixed stars; and as this latter immense starry bed, is not of equal breadth and lustre in every part, nor runs on in one straight direction, but is curved, and even divided into two streams, along a very considerable portion of it. We may likewise expect the greatest variety in the strata of the clusters of stars and nebulae.

“One of the nebulous beds is so rich, that in passing through a section of t in the time of only 36 minutes, no less than 31 nebulae have been detected, all distinctly visible on a fine blue sky. Their situation and shape, as well as condition, seem to denote the greatest variety imaginable. In another stratum or perhaps a branch of the former, I have often seen double and treble nebulae variously arranged; large ones with small seeming attendants ; narrow but much extended lucid nebulae or bright dashes; some of the shape of a fan resembling an electric brush issuing from a lucid point; others of a comatic shape, with a seeming nucleus in the centre, or like cloudy stars, surrounded by a nebulous atmosphere: a different sort again, contain a nebulosity of the milky kind, like that wonderful inexplicable phenomenon about Orion is while others shine with a fainter mottled kind of light, which denotes their being resolvable into stars.

“It is very probable that the great stratum called the milky way, is that in which the sun is placed, though perhaps not in the very centre of its thickness. This we gather from the appearance of the galaxy, which seems to encompass the whole heavens, as it certainly must do, if the sun is within the same. For suppose a number of stars arranged between parallel planes indefinitely every way, but at a given considerable distance from one another, and calling this a siderial stratum; an eye placed somewhere within it, will set all the stars in the direction of the planes of the stratum, projected into a great circle, which will appear lucid on account of the accumulation of the stars, while the’ rest of the heavens at the sides, will only seem to be scattered over with constellations, more or less crowded, according to the distance of the planes, or number of stars contained in the thickness or sides of the stratum. If the eye were placed somewhere without the stratum at no great distance, the appearance of the stars within it, would assume the form of one of the lesser circles of a sphere, which would be more or less contracted to the distance of the eye; and if this distance were exceedingly increased, the whole stratum might at last be drawn together into a lucid spot of any shape, according to the position, length, and height of the stratum. Let us now suppose that a branch or smaller stratum should run out from the former in a certain direction, and let it also be contained between two parallel planes, extended indefinitely onwards, but so that the eye may be placed in the great stratum, somewhere before the separating and not far from the place where the strata are still united; then will the second stratum not be projected into a bright circle like then will former, but will be seen as a lucid branch proceeding from the first, and returning to it again at a certain distance less than a semicircle. What has been instanced in parallel planes may easily be applied to strata irregularly bounded, and running in various directions ; for their projection will of consequence vary, according to the quantities of the variations in the strata, and the distance of the eye from the same and thus any kind of curvatures, as well as various degrees of bright. ness, may he produced in the projections.

“From appearances, then, as I observed before, we may infer, the sun is most likely placed in one of the great strata of the fixed stars, and very probably not far from the place where some smaller stratum branches out from it. Such a supposition will satisfactorily and with great simplicity, account for all the phenomena of the milk way; which, according to this hypothesis, is no other than the appearance of the projection of the stars contained in this stratum, an its secondary branch. As a farther inducement to look on the galaxy in this point of view, let it be considered, that we can no longer doubt of its whitish appearance arising from the mixed lustre of the numberless stars that compose it. Now should we suppose it to be and irregular ring of stars, in the centre nearly of which we must suppose our sun to he placed, it will appear not a little extraordinary, that the sun being a fixed star like those which compose this imagined ring, should just be in the centre of such a multitude of celestial bodies without any apparent reason for this singular distinction; whereas on the other supposition, every star in this stratum, not very near the termination of its length or height, will be so placed as to have its own galaxy, with only such variations in the form and lustre of it, as it may arise from the particular situation of each star.”

A continued series of observations confirmed Dr. Herschel in these opinions; and in a succeeding paper, he has given a sketch of his ideas of the interior construction of the starry heavens.—” That the milky way (says he,) is a most extensive stratum of stars of various sizes, admits no longer of the least doubt; and that our sun is one of the heavenly bodies belonging to it, is equally evident. I have now viewed and gauged this shining zone in almost every direction, and find it composed of shining stars, whose number, by the account those gauges, constantly increases and decreases, in proportion to its apparent brightness to the naked eye.

“But in order to develope the ideas of the universe, that have been suggested by my late observations, it will be best to take the subject from a point of view at a considerable distance both of space then suppose numberless stars of various sizes and time. Let us then suppose numberless stars of various sized, scattered over an infinite space, in such a manner as to be almost divided through whole. The laws of attraction, which no doubt extend to the remotest regions of the fixed stars, will operate in such a manner most probably to produce the following remarkable effects.

1. It will frequently happen, that a star being considerably larger than its neighbouring ones, will attract them more than they will be attracted by others that are immediately around them; by which means they will be in time, as it were, condensed about a centre; or in other words form themselves into a cluster of stars of almost a globular figure, more or less regularly so according to the size and original distance of the surrounding stars. The perturbations of the mutual attractions must undoubtedly be very intricate, as we may comprehend, by considering what Sir Isaac Newton has said, (Princip. Lib i. Prob. 38. et seq.) but in order to apply this great author’s reasoning, of bodies moving in ellipses, to such as are here for a while supposed to have no other motion, than what their mutual gravity has imparted to them, we must suppose the conjugate axes of their ellipses indefinitely diminished, whereby the ellipses will become straight lines.

2. The next case which will happen almost as frequently as the former, is where a few stars, though not superior in size to the rest, may chance to be rather nearer each other than the surrounding one, for here also will be formed a prevailing attraction in the combined center of gravity of them all, which will occasion the neighbouring stars to draw together; not, indeed, so as to form a regular globular figure, but, however, in such a manner as to be condensed towards the common centre of gravity of the whole irregular cluster. And this construction admits of the utmost variety of shapes, according to the number and situation of the stars, which first gave rise to the condensation of the rest.

3. “From the composition and repeated conjunction of both the foregoing forms, a third may be derived: when many large stars, or combined small ones, are situated in long extended, regular, or crooked hooks, or branches; for they will also draw the surrounding ones, so as to produce figures of condensed stars coarsely similar to the former, which gave rise ~o these condensations.

4. ‘We may likewise admit of still more extensive-combinations; same time a cluster of stars are farming in one part of space, there may be another collecting in a different, but perhaps not The distant quarter, which may occasion a mutual approach towards this common centre of gravity.

5. “In the last place, as a natural consequence of the former cases, there will be great cavities, or vacancies, formed by the retreat of the stars towards the various centres which attract them; so that, upon the whole, there is evidently a field of the greatest variety for the mutual and combined attractions of the heavenly bodies to exert themselves in. .

“From this theoretical view of the heavens, which has been takes from a point not less distant in time than in space, we will now retreat to our own retired station, in one of the planets attending a star in great combination with numberless others; and in order to investigate) what will be the appearance from this contracted situation, let us begin with the naked eye. The stars of the first magnitude being in all probability the nearest, will furnish us with a step to begin our scale Setting off therefore, with the distance of Sirius or Arcturus, for instance as unity, we will at present suppose, that those of the second magnitude are at double, those of the third at treble the distance, &c. Taking it for granted then, that a star of the 7th magnitude (the smallest supposed visible with the naked eye) is about 7 times as far: as one of the first, it follows, that an observer, who is inclosed in a globular cluster of stars, and not far from the centre, will never be able with the naked eye to see the end of it; for since according to the above estimation, he can only extend - his view to about 7 times the distance of Sirius, it cannot be expected that his eyes should reach the borders of a cluster, which has perhaps not less than 50 stars in depth every where around him. The whole universe to him, therefore will be comprised in a set of constellations, richly ornamented with scat-tered stars of all sizes; or, if the united brightness of a neighbouring cluster of stars should, in a remarkable clear night reach his sight, it will put on the appearance of a small, faint, whitish, nebulous cloud, not. to be perceived without the greatest attention.

“Let us suppose him placed in a much extended stratum, or branching cluster of millions of stars, such as may fall under the third form, of nebulae already considered. Here also the heavens will not only be richly scattered over with brilliant constellations, but a shining zone, or milky way will be perceived to surround the whole sphere of the heavens, owing to the combined light of those stars which are too small, that is, too remote to be seen. Our observer’s sight will be 80 confined, that he will imagine this single collection of stars, though be does not even perceive the 1000th part of them to be the whole contents of the heavens.

Allowing him now the use of a common telescope, he begins to suspect that all the milkiness of the bright path which surrounds the sphere, may be owing to stars. He perceives a few clusters of them in various parts of the heavens, and finds also, that there are a kind of nebulous patches: but still his views are not so far extended as to reach the end of the stratum in which he is situated; so that he looks upon these patches as belonging to that system, which to him seems to comprehend every celestial object. He now increases his power of vision; himself to a close observation, finds that the milky way is indeed no other than a collection of very small stars. He perceives that those objects which had been called nebulas, are evidently nothing but clusters of stars. Their number increases upon him; anti when he resolves one nebulas into stars, he discovers ten new ones which lie cannot resolve He then forms the idea of immense strata of fixed stars, of clusters of stars, and of nebulas, till going on with such interesting observations, he now perceives that all these appearances must naturally arise from the confined situation in which we are placed. Confined it may justly be called, though in no less a space than what appeared before, to be the whole region of the fixed stars, but which now has assumed the shape of a crooked branching nebula; not indeed one of the least, but perhaps very far from being one of the most considerable, of those numberless clusters that enter into the construction of the heavens.”

Herschel shows, that this theoretical view of the heavens is perfectly consistent with facts, and seems to be confirmed by a series of observations. Many hundreds of nebulas of the first and second forms are to be seen in the heavens ; and their places, he says, will hereafter be pointed out; many of the 3d form described, and instances of the 4th related; a few of the cavities mentioned in the 5th particularized, though many more have been already observed ; so that, upon the whole (says he) “ I believe it will be found, that the foregoing theoretical view, with all its consequential appearances, as seen by an eye inclosed in one of the nebulas, is no other than a drawing from nature, wherein the features of the original have e been closely copied: and I hope the resemblance will not be called a bad one, when it is considered how very limited must be the pencil of an inhabitant of so small and retired a portion of the infinite system, in attempting the picture of so unbounded an extent.”

The doctor having determined that the visible system of nature, by us called the Universe, consisting of all the celestial bodies, and many more than can be seen by the naked eye, is only a group of stars or suns, with their planets, constituting one of those patches called a nebula, and perhaps not one ten thousand millionth part of what is really the universe, he goes on to-delineate the figure of this vast nebula, which he is of opinion may now be done; and for this purpose, lie gives a table, calculating the distance of the stars which form its extreme boundaries, or the length of the visual ray in different parts, by the number of stars contained in the field of his telescope at different times. He then proceeds to offer some thoughts on the origin of the nebulous strata of the heavens; in doing which, he gives some hints concerning the antiquity of them.

If it were possible (says he) to distinguish between the parts of a indefinitely extended whole, the nebulae we inhabit, might be said be one that has fewer marks of antiquity, than any of the rest. explain this idea, perhaps more clearly, we should recollect, that condensation of clusters of stars, has been ascribed to gradual approach and whoever reflects on the number of ages that must hive passed before some of the clusters that are to be found in my intended catalogue of them, could be so far condensed as we find them at present will not wonder if I ascribe a certain air of youth and vigour, to very regularly scattered regions of our siderial stratum. There are moreover, in my places in it, in which, if we may judge from appearances, there is the greatest reason to believe, that the stars are drawing towards secondary centres, and will in time separate into clusters so as to occasion many subdivisions.

“ Here we may surmise, that when a nebulous stratum consists chiefly of nebulas of the first and second forms, it probably owes origin to what may be called the decay of a great compound nebula of the third form ; and that the subdivisions which happened to it, it length of time occasioned all the small nebulas which sprung from it to lie in a certain range, according as they were detached from the primary one. In like manner, our system, after numbers of ages, may very possibly become divided, so as to give rise to a stratum of two or three hundred nebulas ; for it would not be difficult to point out so many beginning or gathering clusters in it. " This throws a considerable light, upon that remarkable collection of many hundreds of nebulas which are to be seen in what I have called the nebulous stratum in Coma Berenices. It appears from the extended and branching figure of our nebula, that there is room for the decomposed small nebulas, of a large, reduced, former great one, to approach nearer to us in the sides, than in any other part. Nay, possibly there might originally be another very large joining branch,-which in time became separated by the condensation of the stars: and this may be the reason of the little remaining breadth of our, system in that very place; for, the nebulas of the Coma are brightest and most crowded just opposite to our situation, or in the pole of the system.

“As soon as this idea was suggested, I tried also the opposite pole where, accordingly, I have met with a great number of nebulas, though under a much more scattered form. Some parts of our system, indeed, seem already to have sustained greater ravages of time than others; for instance, in the body of the Scorpion, in an opening which is probably owing to this cause. It is at least 4 broad; but its height I have not yet ascertained. It is remarkable, that the 80 Nebuleuse sans Etoiles of the Connoissance des Temps; which is also on the western border of another vacancy, and has, moreover, a small miniature cluster or easily resolvable nebula, of about 2 minutes north. Following it at no very great distance.

There is a remarkable purity or clearness in the heavens, when we look out of our stratum at the sides ; that is towards Leo, Vergo, and Coma Berenices on the one band, and towards Cetus on the other;; where as the ground of the heavens becomes troubled as we approach towards the length or height of it. These troubled appearances are easily to be explained by ascribing them to some of the distant straggling stars that yield hardly light enough to be distinguished: and I have indeed, often experienced this to be the cause, by examining the spots for a long while together, when at last I generally perceived the stars which occasioned them. But, when we look towards the poles of our system, where the visual ray does not graze along the side the straggling stars will of course be very few in number; and therefore, the ground of the heavens will assume that purity which I have always observed to take place in those regions.”

The doctor here applies the name of poles to those points which are 90 distant from a circle passing along the milky way. The north poles is situated in R. As. 186 and distant from the pole of the world 58.

According to Herschel, then, the universe consists of nebulas, or innumerable collections of innumerable stars, each individual of which is a sun, not only equal, but much superior to ours: and none of the celestial bodies in our nebulas are nearer to one another, than we are to Sirius, whose distance is supposed to be not less than 400,000 times that of the sun from us, or 38 millions of millions of miles. The whole extent of the nebulas being in some places near 500 times as great, must be such, that the light of a star placed at its extreme boundary, supposing It to fly with the velocity of 12 millions of miles every minute must, have taken near 3000 years to reach us. Herschel, however is by no means of opinion that our nebula is the most considerable in the universe.

“As we are used (continues he) to call the appearance of the heavens, where it is surrounded with a bright zone, the milky way, it may not be amiss to point out some other very remarkable nebulas, which cannot well be less, but are probably much larger, than our own system; and being also extended, the inhabitants of the planets

That attend the stars which compose them, must likewise perceive the same phenomena; for which reason they may also be called milky ways. For distinction’s sake. My opinion of their size is grounded on the following observations. There are many round nebulas of the first form, of about five or six minutes in diameter, the stars of which I can see very distinctly ; and on comparing them with the visual ray calculated from some of my long gauges, that the centres of these round nebula may be 600 times the distance of Sirius from us.”

He then tells us, that the stars in such nebulae, are probably twice as much condensed as those of our system: otherwise, the centre of it could not be less than 6000 times the distance that Sirius is from us; and that it is possibly much under-rated, by supposing it only 600 times the distance of that star.

“ Some of these round nebulas (says the Dr.) have others near them, perfectly similar in form, colour, and the distribution of stars, but of only half the diameter: and the stars in them seem to he doubly crowded, and only at about half the distance from each other. They are indeed so small, as not to he visible without the utmost attention. I suppose these nebulas to be double the distance of the first.

An instance equally remarkable and instructive is, a case-, where, in the neighbourhood of two such nebulas as have been mentioned, I met with a third similar, resolvable, but much smaller and fainter nebulas, the stars of it are no longer to be perceived, but a resemblance of colour with the former two, and its diminished size and light may well permit us to place it at full twice the distance of the first. And yet the nebulosity is not of the milky kind; nor is it so much as difficulty resolvable or colourless. Now in a few of the extended nebulas, the light changes gradually, so as from the resolvable to approach to the milky kind ; which appears to me an indication, that the milky light of nebulas is owing to their much greater distance. A nebula therefore, whose light is perfectly milky cannot well be supposed to be at less than 6000 or 8000 times the distance of Sirius; and though the numbers here assumed are not to be taken otherwise, than as very coarse estimates, yet an extended nebula, which an oblique situation, where it is possibly fore-shortened by one half, two thirds, or three fourths of its length, subtends a degree or more in diameter, cannot be otherwise than a wonderful magnitude. and may well out-vie our milky way in grandeur.”

After giving an account of several remarkable nebulas, Dr. Herschel concludes thus: “Now what great length of time must be required to produce these effects (the formation of nebulas) may easily be conceived, when, in all probability, our whole system, of about 800 stars in diameter, if it were seen at such a distance, that one end of it might assume the resolvable nebulosity, would not at the other end. present us with the irresolvable, much less with the colourless and milky nebulosities.” Great indeed must be the length of time, requisite for such distant bodies to form combinations by the laws of attraction, since, according to the distances. the Dr. has assumed, the light of some of his nebulas must be 36,00(J or 48,000 years in arriving from them to us. It would be worth while-then to inquire, whether attraction is propagated in time or not, or whether it moves quicker or slower than light.

Several circumstances, however, lie says manifestly Lend to a general preservation. The indefinite extent of the siderial heavens must produce a balance, that will effectually secure all the great parts of the whole from approaching to each other. “There remains then (says he) only to see how the Particular stars belonging to separate clusters, are prevented from rushing on to their centres of attraction.” this he supposes may be done by projectile forces. “The admission of which will prove such a barrier against the seeming destructive power of attraction, as to secure from it, all the stars belonging to a cluster, if not for ever at least for millions of ages Besides, we ought perhaps to look upon such clusters, and the destruction of a star now and then in some thousands of ages, as the very means by which the whole is preserved and renewed. These clusters may be the laboratories of the universe, wherein the most salutary remedies for the decay of the whole are prepared.”

The existence of such projectile forces is rendered probable, from the apparent changes of position of certain stars, and from a comparison of the best modern observations, with the most accurate of former times, there appears to have been a real change in the places of some of them. The Bull’s Eye, Sirius, and Arcturus, are now found to be half a degree more southerly than the ancients reckoned them, and the bright star in the shoulder of Orion, has, in Ptolemy, almost a whole degree of latitude more southerly than at present. Dr. Herschel has lately observed that the distance and position of the two stars forming the double star, in Draconis, is different from what it was in Flamstead's time. So considerable is the change of distance (for it is 16".6) that he thinks we can hardly account for it otherwise, than by admitting a proper motion in the one or other of the stars or in our solar system; most probably he says, neither of the three are at rest.

If our solar system do really change its place in absolute space, in process -of time, an apparent change in the angular distances of some of the fixed stars will appear-; and the nearest being more affected than such as are more remote, their relative positions may be seen to alter, although the stars were really immoveable. and vice versa, we may surmise, from the observed motions of the stars, that our sun with all its planets and comets, may have a motion towards some particular part of the heavens, on account of a greater quantity of matter collected in a number of stars, and their surrounding planets there situated, which may occasion a gravitation of our whole solar system towards it. On the other hand, if our system he at rest, and any of the stars really in motion, this might likewise vary their apparent position, and the more so, the nearer they are to us, or. the swifter their motions ‘are, or the more proper the direction of the motion is, to be rendered perceptible by us.

From this brief theoretical sketch, we derive an idea, which the ancient philosophy would not give us, of the amazing grandeur, magnificence, and sublimity of universal being: all the visible part of, which, is hut a mere speck, a comparatively little, branching fragment of the extended universe. And although it is impossible for us to attain to an identifying sensibility, and actual retrospect, in consequence of our limited situation, yet there is every reason to conclude, from analogy, observation, and reflection, that infinite space is thus occupied, and diversified, and that God is a God of the universe, and not merely of this little, straggling world of ours; which is but a little planet, attached to a single star, which appears somewhat eccentrized, from the -regular strata of worlds, and which we have been in the habit of contemplating, as of vast and superior magnitude.

It is a narrow, contracted, and local idea, that limits the boundaries of universal creation, to this little ball of earth, or this little solar system, of which we are a comparatively small member. The idea would appear more rational, and consistent, and more worthy of the munificent hand, that guides the stars in their courses, and grasps them in its palm, that could contemplate not only our own system, but the whole visible universe as a mere link of an infinitely extended system of being. But there is no error, the mind is more prone to, than, to substitute local, for general ideas; and to limit the boundaries of infinite being, to its own finite comprehension. Whereas, it does appear most reasonable, if we apply our mind to a right contemplation of things, and avail ourselves of the analogy of experience and fact, that nature travels on in infinitum. and is equally boundless in magnitude, and prolific in variety.

A late important discovery was made by the celebrated Dr. Bradley, astronomer royal, of the aberration of the fixed stars; this was accidentally made, while endeavouring to ascertain the parallax of be earth’s orbit. This is a variation of their situation, in relation to the plane of the earth’s axis. Mr. Molyneuz and Dr. Bradley began to observe the bright star in the head of Draco, as it passed near the zenith, with an instrument made by Mr. Graham, for the purpose of discovering the parallax, and by often repeated observations, they found the star, about the beginning of March 1726, to be 20 seconds more southerly thin at the time of the first observation. It now indeed seemed to have arrived at its utmost limit southward ; because in several trials made about this time, no sensible difference was observed in its situation. : by the middle of April it appeared to he returning back again towards the north ; and about the beginning of June, it passed about the same distance from the zenith, as it had done in December, when it was first observed. In September following it appeared 39” more northerly than it was in March, just the contrary way to which it ought to appear by the annual parallax of the stars. This unexpected phenomenon perplexed the observers very much, and Mr. Molyneux died before the true cause of it was discovered. After this Dr. Bradley. with another instrument, more exact, and accurately adapted to the purpose, observed the appearances, not only in that, but many other stars ; and by the great regularity that appeared in a series of observations, made in ;J1 parts of the year. the doctor was full) satisfied with regard to the general laws of the phenomenon, and therefore endeavoured to find out the cause of them. He was already convinced that the apparent motion of the stars, was not owing to a mutation of the earth’s axis. The next thing that offered itself was an alteration in .the direction of the plumb line, by which the instrument was constantly rectified; but this proved insufficient, as well as a trial by refraction. At last this acute astronomer found, that the phenomena in question proceeded from the progressive motion of light, and the earth’s annual motion in its orbit: for he perceived, that if light was propagated in a given portion of time, the apparent place of a fix d object would not be the same when the eye is at rest, as when it is moving in any other direction, than that of the line passing through the eye and the object; and, that, when the eye is moving in different directions, the apparent place of the object would be different, from the true.

10th. The earth, or planet which we inhabit, is the third in magnitude and distance from the sun. it is computed to he 95.173,000 miles distant from the centre of its attraction, or the body of the sun; round which it revolves in the space of 365 days 5 hours and 49 minutes, or from any equinox, or solstice to the same again, but from any fixed star to the same again as seen from the sun, in 365 days 5 hours 9 minutes ; the former being the length of the tropical year, and the latter the length of the siderial. It travels at the rate of 68,000 miles every hour; a motion, which though upwards of 140 times swifter than a cannon ball, is little more than half as swift as Mercury’s motion in his orbit. The diameter of the earth is 7970 miles; and by turning round on its axis every 24 hours from west to east it causes an apparent motion of all the heavenly bodies from east to west. By this rapid motion of the earth on its axis, the inhabitants about the ‘equator are carried 1042 miles every hour, while those on the parallel of London are carried only about 580, besides the 68 thousand above mentioned, which is common to all places whatever

A variety of circumstances afford the clearest evidence of the globular figure of the earth. 1. When we are at sea, we may be out of sight of land, even when the land i3 near enough to be visible, if it were not hid from the eye by the convexity of the water. 2. The higher the eye, the farther will the view be extended; it is very common for sailors to go up to the top of the mast to look out, as they term it, and thence they will discover land, or ships at a much greater distance than one could do from the deck. 3. When we are on shore, the highest part of a ship is visible at the greatest distance. If a ship is going from us, out to sea, we shall continue to see the mast, after the hull or body has disappeared, and the top of the mast will continue to he seen the longest. If a ship is coming towards us, the top of the mast comes first in view, and we see more and more, till at last the hull appears 4. Several navigators, as Ferdinand Magellan, Sir Francis Drake, Lord Anson, Captain Cook, &c. have sailed round the globe; not in an exact circle, the land preventing them, but by going in and out as the shores happen to lie. 5. All the appearances of the heavens are the same, whether at land or sea. 6. Eclipses of the moon arise from the shadow of the earth, which is always circular, although the earth presents, during several hours, different portions of its surface to the moon, yet still the shadow is round. The small inequalities upon the surface of the earth, bear no kind of proportion to its magnitude, sufficient to alter the appearance of its shadow. 7. The globular figure of the earth is also inferred from the operation of level ling in which it is found necessary, to make an allowance for the difference between the apparent, and true level.

The earth’s axis makes an angle of 23 1/2 with the axis of its orbit, and its position at any one time, is parallel to its position at any other time. Thus it points always to the same quarter of the heavens throughout its annual course. That the earth moves round the sun, may be proved beyond a doubt, by the following arguments.

1st. The sun is found by the most accurate observations, to be immensely larger than the earth; for his diameter, as seen by us, subtends an angle of more than 80’, but it is certain, that the earth were it seen from the sun, would not subtend a greater angle than 1 7”, if, therefore, the sun be formed of materials, not very much rarer than the earth, (and there is no reason to believe it is less dense,) the quantity of matter in the sun, must far exceed the whole mass of matter in all the planets; and to suppose that gravity retains all the other planets in their orbits, without affecting the earth, would be as absurd, as to suppose that six cannon bullets might be projected up to different heights in the air, and that five of them should fall to the ground, and that the sixth, though neither the highest nor the lowest, should remain suspended in the air, without falling, and the earth move round it.

There is no such thing in nature as a heavy body moving round a light one, as its centre of motion. A pebble fastened to a millstone by a string, may, by an easy impulse be made to circulate round the millstone: but no impulse could make a millstone circulate round a loose pebble; for the millstone would fly off and carry the pebble along with it. The sun is so much bigger and heavier than the earth, that, if he were moved out of his place, not only the earth, but all the planets, even if they were united in one mass, would be carried along with him, as the pebble would be with the millstone.

2. The celestial motions, on this principle become more simple and free of looped contortions, which must be supposed to occur in the other case; and which are extremely improbable, and incompatible with all that we know of motion. 3. If the earth revolve round the sun, then the analogy between the squares of the periodic times, and the cubes of the distances, will obtain in all the bodies, which circulate round a common centre ; whereas this will not be the case with the sun and moon, if both turn round the earth. Besides these, other proofs night be given: but the most complete proof of all, and which indeed amounts to a demonstration is, the aberration of the fixed stars, arising from the progressive motion of light, combined with the earth’s progressive motion round the sun, a discovery made by Dr. Bradley, and one of the finest in modern astronomy.

The strongest objection, that can be urged against the earth’s moving round the sun like the other planets, is that in opposite points of the earth’s orbit, its axis, which always keeps a parallel direction, would point to different fixed stars; which is not found to be fact. But this objection is easily removed, by considering the immense distance of the stars, in respect to the diameter of the earth’s orbit; the latter being no more than a point, when compared to the former. If we lay a ruler on the side of a table, and along the edge of the ruler, view the top of a spire at ten miles distance; then lay the ruler on the opposite side of the table, in a parallel situation to what it had before, and the spire will still appear along the edge of the ruler; because, our eyes even when assisted by the best instruments, are incapable of distinguishing so small a change at so great a distance. As the apparent places of the stars, therefore, correspond with this theory, the motion of the earth, and the motion of light are at once determined.

For by frequent observations of the eclipses of Jupiter’s satellites, it is found, that light is about 8 minutes in moving from the sun to the earth. And since the earth describes about I degree, or 3800’ in a day, or 1440 miles in minutes, it will describe 20” in its orbit; therefore, the velocity of light, is to the velocity of the earth in its orbit, as radius to an arch of 20”, or the third part ofa minute, that is, as one to 0002929/3 or, .00009697, or as 10,300 to 1, that is, the velocity of light is I 0,300 times greater than the velocity of the earth in its orbit.

It is found that the sun, and those planets which have visible spots turn round on their own axes: for the spots in general move regular over their disks, allowing for the variations already noticed. Hence %ve may reasonably conclude, that the other planets on which we see no spots, and the earth which is likewise a planet, have such rotations. ‘But being incapable of leaving the earth to view it at a distance, and its rotation being smooth and uniform, we can neither see it move on its axis as we do the planets, nor feel ourselves affected by its motion.

Yet there is one effect of such motion, which will enable us to judge with certainty, whether the earth revolves On its axis or not.

All globes which do not turn round their axis, will be perfect spheres, on account of the equable pressure on their surface ; especially of the fluid parts. But all globes, which turn on their axis, will be oblate spheroides; that is their surface will be higher, or farther from the centre in the equatorial than in the polar regions: for as the equatorial parts move quickest, they will recede farthest from the axis of motion and enlarge the equatorial diameter. That our earth is really of this figure, is demonstrable from the unequal vibrations of a pendulum, and the unequal length of degrees in different latitudes -Since then, the earth is higher at the equator than at the poles, the sea, which naturally runs downwards, or towards the places which are nearest the centre, would run towards the polar regions, and leave the equatorial parts dry, if the centrifugal tbrce of those parts, by which the waters were carried there, did not keep them from returning. The earth’s equatorial diameter, is 36 miles longer than its axis.

It is found that bodies near the Poles are heavier than those towards the equator, because they are nearer the earth’s centre, where the whole force of the earth’s attraction is accumulated. They are also heavier, because their contrifugal force is less, on account of their diurnal motion being slower. For both these reasons, bodies carried from the poles towards the equator, gradually loose their weight. Experiments prove, that a pendulum which vibrates seconds near the poles, vibrates slower near the equator, which shows that it is lighter, or less attracted there. To make it oscillate in the same time, it is found necessary to diminish its length. By comparing the different length of pendulums, swinging seconds at the equator and at London, it is found, that a pendulum must be 2 169/1000 lines (or 12th part of an inch) shorter at the equator than at the poles.

A person on the earth can no more be sensible of its undisturbed motion on its axis, than one in the cabin of a ship, on smooth water, can be sensible of the ship’s motion, when it turns gently and uniformly round. It is therefore no argument against the earth’s diurnal motion, that we do not feel it; nor are the apparent revolutions of the celestial bodies every day, a proof of the reality of these motions; for whether we, or they revolve, the appearance is the very same. A person looking through the cabin window of a ship, as strongly fancies the objects on land to go round, when the ship turns, as if they were actually in motion.

The other common objections against the earth’s motion on its axis, are easily answered. Some imagine, that if the earth turns eastward, as it actually does, if it turns at all, that a ball fired perpendicularly up in the air, should fall considerably westward of the place it was projected from. This objection will be found to have no weight, if we consider that the gun, and ball, both partake of the earth’s motion: and therefore, the ball being carried forward with the air, as quick as the earth and the air turn, must fall down on the same place. A stone let fall from the top of a main-mast, if it meets with no obstacle, the deck as near the foot of the mast, when the ship sails smoothly along, as when it stands still.

for those scriptural expressions which seem to contradict the earth’s motion, this general answer may be made to them all, that, the scriptures were never intended to instruct us in philosophy, or astronomy; and therefore, on those subjects, expressions are not always to be taken in the literal sense, but for. the most part, as accommodated to the common apprehension of mankind. Men of sense, in all ages, when not treating of the science purposely, have used common language, and it would be absurd to adopt any other, in addressing the majority of mankind. The annual motion of the earth has been effectually confirmed by an argument drawn from the progressive motion of light; and from the same consideration, the truth of the diurnal motion may be completely established.

In consequence of the progressive motion of light, the apparent place of a fixed star is east of its true place, and the difference is proportional to the cosine of the stars declination; this displacement of the fixed stars has changed, because of the procession of the equinoctial points. Therefore, if the diurnal revolution of the heavens were a real motion, the whole heavens must have changed their appearance; and the respective positions of the stars must be very different now, from what they were in the time of Hipparchus. A star which is now near the vernal equinox, must have changed its apparent distance at least 50 from another elliptical star which is 60 degrees east of it. Nay it is highly probable, that no zodiacal star could be ever visible; such would have been the direction, that the rays of light must have taken, because of their own proper motion being corn-pounded with that of the star, whose velocity must have been exceedingly great,, by reason of its distance from the poles of the motion. But since no such remarkable displacement of the stars has been observed, we may conclude, that the cause which would have produced it, has no existence; and that the revolutions of the heavens is not a real, but only an apparent motion.

From the preceding select remarks and observations, we derive the following satisfactory conclusions. That the earth is a planet, moving in concert with the other planets, and like them, yielding, and exhibiting all the planetary evolutions, waxing, and waning, and revolving round its primary. That it participates in mutual relations, which are common to the system, of which it is a member. That whatever enters into the composition of the earth, is reciprocated through the system, supplied, and communicated by the current flow of attraction, from globe to globe. That this attraction, is a mutual relation. and Communication between worlds, but that it is diversified in degrees, of strength, as they are diversified in degrees of distance. Hence also we derive the physical conclusion, that two worlds cannot be suspended, and concentrated in the same orbit, or limit of attraction, but that their distances will be in an exact ratio, to the space which they are to occupy: so, that, if two worlds c could coalesce and drop. into one, for instance, the earth and .Jupiter, their new orbit would assume a mean distance, between their separate orbits, somewhere, about the orbit of Mars, and this would occur in consequence of, and in proportion to, the combined attraction of the Two spheres. Could such a phenomenon take place, the new world would immediately assume an orbit, whose distance from its centre would be in proportion to its relative quantity of attraction, to that centre: arid the new world would immediately assume, also, a rotatory motion on its axis, which would be in an exact ratio, to the proportion of its equatorial diameter, and its distance from the centre of revolving motion. Finally, we learn from this general review, that the same extensive and universal relations prevail, through the continuity of divisions, and subdivisions of worlds, and systems of worlds, as if the materials of the universe were spread out in uniform consistence, and rendered independent of the mundane laws of density, and rarefaction; gravitation, and attraction; concretion, and expansion; the general laws of motion and revolution; so that no arguments can weigh against the infinite continuity of worlds, and systems of worlds.

The different seasons which we experience, are owing to the obliquity of the axis of rotation of the earth, to the plane of the earth’s orbit. But if the axis were perpendicular to it, there could be no variety in the length of days, in whatever part of the orbit the earth was; and all seasons would be alike. Thus the obliquity of the earth’s axis, to the ecliptic, or which is the same thing of the equinoctial to the ecliptic, is the cause of the different seasons, summer, winter, spring and autumn, during the year. Without this, there could be no difference of seasons; and consequently it could not be easy to know the length of the year, without observations of the stars. For the length of the year is known from the time of observation, when the sun is in the equinoctial points ; and there being no such points to observe by, there could be no method but to observe by the position of the stars, when the same star was again in opposition to the sun, which none but an astronomer could do.

The sun appears 47 degrees higher in the summer tropic, than it does in the winter tropic; this phenomenon may be thus represented: take a small globe that has the equinoctials and parallels drawn upon it; and placing a candle upon a table, move the globe round the candle in a circle parallel to the table, so that the axis of the equator may be oblique to that circle, and be kept always in a parallel position whilst it moves about. The candle will illuminate the globe as it is carried round, just as the sun does the earth in its orbit; and the parallels will be the same way affected with light and darkness the globe.

The opinion of astronomers, that the orbit of the earth being and the sun constantly keeping in its lower focus, which according to calculation, is, 1,617,941 miles from the middle point of the larger axis, the earth approaches twice as near, or, by computation 3,235;882 miles nearer the sun at one time of the year than at another; for the sun appearing under a larger angle in our winter than in our summer, proves that our earth approaches nearer the sun in winter, than in summer. ‘But here a very serious difficulty occurs, which they appear not to have been aware of, they did not consider in this instance, that whilst it was winter in the northern regions, it was summer in the southern regions of the earth, and that it was impossible, that the earth in 400 of north latitude, could be 3,235,832 miles nearer the sun, than the same earth in 400 of south latitude, the direct difference of which situations, would only amount to a very few miles, in proportion to the angular obliquity of the opposite points of parallel latitudes, north and south; they did not consider, that the part of the earth, which is nearest the sun, is that point on its circumference which has the sun in its zenith at meridian, and that in twelve hours time, that point of its circumference would be farthest from the sun: the angular phenomenon, on which astronomers have founded the hypothesis, vanishes at the equator, and in opposite parallels of latitude, consequently the hypothesis itself falls to the ground.

No part of the earth, can, at the same time, be farther from the sun than another, at a distance exceeding its diameter, or 7964 miles, and that point of the earth which is nearest the sun at meridian, is farthest from it at midnight. One astronomer in 40 of north latitude computes the earth to be 3 1/4 millions of miles nearer the sun, in his northern winter, than it was in his northern summer; while an astronomer, in 40 of south latitude, at the very same instant, and from the very same data, is calculating the same earth to be 3 1/2 millions of miles, farther from the sun than the northern astronomer. while the diameter of the earth itself does not extend to 8000 miles. These remarks are only intended to apply to the hypothesis, that the earth is nearer the sun in winter than in summer, they are not intended to affect, by any means the doctrine of the ellipsis of the earth’s orbit, or to deny its perihelion and aphelion distances. Nor is it intended to deny that the earth is in its perihelion in winter; but it should be recollected, that if the earth is in its perihelion in winter, it is also in its perihelion in summer; for there is no winter but there, is at the same time a summer, and it is evident, that the part where it is summer, is nearer the sun, than the part where it is winter, and this for the reasons before assigned, viz, that of the direct position, of a point of the earth’s circumference to the sun: for the position of all the parts of the earth, where it is summer, is more direct, than the parallel parts where it is winter. Besides, from the nature of an ellipsis, the earth in its complete revolution, must be twice in is aphelion, and twice in its perihelion: and the difference of time will be, half, or the earth will be alternately in its perihelion, and aphelion every six months: consequently, if the earth is in its perihelion in winter, it will also be in its perihelion in summer, for the distance of time is six months, the distance mentioned. And the northern parts of the earth, cannot be in aphelia, at the same time that the southern are in perihelia Therefore, when it is winter in the north, and summer in the south; or summer in the north, and winter in the south, then is the earth in perihelia, then, computing the distance, the earth is 3,235,882 miles nearer the sun, than, when it is in the vernal and autumnal equinoxes: at which seasons, the atmosphere of the earth is more dilated and enlarged, than at the solstices, in consequence of the direct force of attraction, operating on the centre of its disk.

The MOON is not a primary planet, but only a satellite, Or attendant on the earth, circulating round it in 29 days, 12 hours, 44 minutes, and round the sun along with the earth in a year. The moon’s dia. meter is computed at 2180 miles; and her distance from the earth's centre 240,000; the period of her revolution in her orbit is 27 days, 7 hours, 43 minutes, moving at the mean rate of 2290 miles an hour; she is stated to revolve on her axis, in exactly the same time that she moves round the earth, which is the occasion of her exhibiting always the same face to us, and consequently her day and night taken together is as long as our month.

The moon, like the earth, is an opaque globe, and shines by reflecting the light of the sun; therefore whilst that half of her, which is towards the sun is enlightened, the other half must be dark and invisible. Hence she disappears when she comes between us and the sun; because then her dark side is turned towards us. When she is gone a little way forward, we see a little of her enlightened side, which increases to our view as she advances until she comes opposite to the sun; when her whole enlightened side is towards us, and she appears a round illuminated orb, which we call the FULL MOON; her dark side being then turned away from the earth. From the full she seems to decrease gradually, as she goes through the other half of her course, showing us less of her enlightened side every day, till her next change or conjunction with the sun, when she disappears as before.

The earth being an opaque body must appear as a moon, to the inhabitants of the moon, waxing and waning regularly, but appearing 13 times as big, and affording them 13 times as much light as she does changes to us, the earth appears full to her; and when she is in her first quarter to us, the earth is in its third quarter to her, and vice versa. From these peculiar circumstances of the month, the earth is never seen at all from the side opposite to the earth; from the middle of the other half it is always seen over bead; turning round almost 30 times as quick as the moon does. From the circle which our view of the moon, only one half of the earth’s side next her is seen; the other half being hid below the horizon of all places On that circle. To her inhabitants the earth appears the biggest body the universe, appearing full 13 times as big as she does to us.

It has been observed by astronomers that the axis of the moon, is so nearly perpendicular to the ecliptic, that the sun never removes sensibly from the equator; and the obliquity of her orbit, as seen from the sun, which is next to nothing, cannot cause any sensible declination. Yet her inhabitants are not destitute of means for ascertaining the length of their year, or period of her revolution round the sun: though their method must be different from ours. We know the length of our year by the return of our equinox; but the Lunarians having always equal day and night, must have recourse to another method arid we may suppose, they measure their year by observing when either of the poles of our earth begins to be enlightened, and the other to disappear, which always takes place at our equinoxes: being conveniently situated to observe any particular phenomenon attached to our globe, and which must be extremely conspicuous to them. The year is of the same absolute length to the inhabitants of the earth and moon though very different as to the number of days; we having 365,k days, and the Lunarians only 1 27/19 every day and night in the moon, being as long as 29 1/2 on the earth.

The inhabitants of the moon on the side next the earth, may find the longitude of their places, as easily as we can find the latitude of ours: for the earth being constantly or very nearly so, over one meridian of the moon, the east and west distances of places from that meridian are as easily found, as we can find our distances from the equator, by the altitude of our celestial poles.

As the sun only enlightens that half of the earth which is towards it, and leaves the opposite half in darkness, so he does the same to the moon, but with this difference, that as the earth is surrounded with a superior atmosphere, we have twilight after the sun sets, and before he rises; but the moon, (as is supposed,) having no atmosphere of her own, must have an immediate transition from the brightest sunshine to the blackest darkness.

The moon being an opaque spherical body, we can only see to part of her enlightened half, which is towards the earth. And the fore, when the moon is between us and the sun, her dark side is turn towards the earth, and she totally disappears, there being not light enough on that half to render it visible. When she comes to first octant, or has gone an eighth part of her orbit, from her conjunction, a quarter of her enlightened side is towards the earth, and appears horned. When she has gone a quarter of her orbit, in between the earth and the sun, she shows us one half of her enlightened side, and we say she is a quarter old. When she gains he third octant, by showing us more of her enlightened side, she appe gibbous. When she comes to her fourth octant, or has complete half her orbit, she is said to so in opposition to the sun; when t whole of her enlightened side is towards us, and we say it is full mo In her fifth octant, part of her dark side being towards the earth, s again appears gibbous, and is on the decrease. When she comes her sixth octant, we see just one half of her enlightened side, and s. appears half decreased, or as we say in her third quarter. In h seventh octant we only see a quarter of her enlightened side, when she again appears horned. At length having completed her course fr the sun to the sun again, she disappears; and we say it is new mo Thus in going through her first four octants, the moon continually seems to increase; and in her remaining four octants, to decree in the same proportion, having like phases at equal distances: but seen from the sun, or from Mercury, she appears always in the full.

The moon does not appear perfectly round when she is full i the highest or lowest part of her orbit, because we have not a fill view of her enlightened side at that time. When full in the higher part of her orbit, a small deficiency appears on her lower edge; a the contrary when full in the lowest part of her orbit.

It is evident, that when the moon changes to the earth, the earth in full to the moon, and vice versa. For when the moon is new to the earth, the whole enlightened side of the earth is towards the moon. And when the moon is full to the earth, its dark side is towards her Hence a new moon answers to a full earth, and a full moon to a earth. The quarters are also reversed to each other.

The position of the moon’s cusps, or a right line touching the moon’s horns, is very differently inclined to the horizon, at different hours of the same days of her age. Sometimes she stands, as it were, upright on her lower horn, and then such a line is perpindicular to the horizon: when this happens, she is in what the astronomers call the nonagesimal degree ; which is the highest point of the ecliptic. But this never happens when the moon is on the meridian, except she is at the very beginning of cancer, or Capricorn.

It appears that the moon turns round her axis in the time she goes round her orbit and that a spectator at rest without the periphery of the moon's orbit would see all her sides turned regularly towards him in that time. She turns round her axis from any star, to the same star again in 27 days 8 hours; from the sun to the sun again, in 29 1/2 days; the former is the length of her siderial day, and the latter the length of her solar day. A body moving round the sun would have a solar day in every revolution, without turning on its axis; the same as if it had at rest, and the sun moved round it: but without moving round its axis, it could never have one siderial day, because it would always keep the same side towards any particular star.

If the earth had no annual motion, the moon would go round it, so, to complete a lunation, a siderial, and a solar day, all in the same time. •But because the earth goes forward in its orbit, while the moon goes round the earth in her orbit, the moon must go as much more than round her orbit, from change to change, in completing a solar day, as the earth has gone forward in its orbit during that time, almost a twelfth part, of a circle. If the earth had no annual motion, the moon’s motion round the earth, and her track in open space, would be always the same. But as the earth and moon move round the sun, the moon’s real path in the heavens, is very different from, her visible, path round the earth; the latter being in a progressive circle, and the former in a curve of different degrees of concavity ; which would always be the same, in the same parts of the heavens, if the moon performed a complete number of lunations in a year without any fraction.

To illustrate this, let the nail in the end of the axle of a chariot wheel, represent the earth. and a pin in the nave, the moon: if the body of the chariot be propped up so as to keep the wheel from touching the ground, and the wheel be then set in motion, the pin will then describe a circle both round the nail, and in the space it moves through. But if the prop be taken away, the horses put to, and the chariot driven over a l)iece of ground, which is circularly convex, the nail in the axle will describe a circular curve, and the pin in the nave will still describe a circle round the progressive nail in the axle, but not in the space through which it moves. In this case the curve described by the nail, will resemble in miniature, as much of the earth’s annual path round the sun, as it describes while the moon goes as often round the earth, as the pin does round the nail: and the curve described by the pin, will have some resemblance of the moon’s path during so many lunations.

Many conjectures have been formed respecting the moon’s substance. Some have imagined that besides the light reflected from the sun, the moon hath also some, obscure light of her own, by which she would be visible without’ being illuminated by the sun's beams; in proof of this it is urged, that during the time of even total eclipses, the moon is still visible, appearing of a dull red colour, as if obscured by a great deal of smoke. In reply to this it bath been advanced, that this is not always the case ; the moon sometimes disappearing, totally in the time of an eclipse, so as not to be described by the best glasses, while little stars of the fifth and sixth magnitudes were distinctly seen as usual: and when the moon is visible in a total eclipse a sufficient reason may be assigned for this appearance, from the refraction of the sun’s rays through our atmosphere, which are reflected back on the earth, by the otherwise dark surface of the moon.

It has been a matter of much dispute, whether the moon has an atmosphere or not; the following arguments have been urged on the negative side. I. The moon constantly appears with the same brightness where there are no clouds in our atmosphere; which could not be the case, if she were surrounded with an atmosphere like ours, so variable in its density, and so frequently obscured by clouds and vapours. 2. In an appulse of the moon to a star, when she comes so near it that a part of her atmosphere is interposed between our eye and the star, refraction would cause the latter to seem to change its place; so that the body of the moon would appear to touch it later than by her own motion she would do. 3. Some philosophers are of opinion, that because there are no seas and lakes, and consequently no springs and rivers in the moon, there is therefore no atmosphere, as there is no water to be raised up in vapours.

To these arguments it has been replied. I. That the moon does not always appear with the same brightness, even when our atmosphere appears equally clear. Hevelius relates, that he has several times found i n skies perfectly clear, when even stars of the 6th and 7th magnitude were visible, that at the same altitude of the moon, and the same elongation from the earth, and with one and the same telescope, that the moon and maculae do not appear equally lucid, clear, and conspicuous at all times; but are much brighter, and more distinct at some times than at others. From the circumstances of this observation, say they, it is evident, that the reason of this phenomenon is neither in our air, in the tube, in the room, nor in the spectator’s eye; but must be looked for in something existing about the moon. An additional argument is drawn from the different appearances of the moon in total eclipses, which are supposed to be owing to the different constitutions of the lunar atmosphere.

2. To the second argument, Dr. Long replies, that Sir Isaac Newton has shown, that the weight of any body upon the moon is but a third part of what the same would be upon the earth: now the expansion of the air is reciprocally as the weight that compresses it; the air, therefore, surrounding the moon, being pressed together by a weight, or being attracted towards the centre of the moon, by a force equal only to one third of that which attracts our air towards the centre of the earth, it ‘follows, that the lunar atmosphere is only one third as dense as that of the earth, which is too little to produce any sensible refraction of the stars’ light. Other astronomers have contended that such refraction was sometimes very apparent. Cassini says, that he frequently observed Saturn, Jupiter and the fixed stars, to have their circular figure changed into an elliptical one, when they approached either to the moon’s dark or illuminated limb, though they own, that in other occultations, no such change could be observed. With regard to the fixed stars, indeed, it has been urged, that granting the moon to have an atmosphere, of the same nature and quantity as ours, no such effect- as a diminution of light ought to take place; at least, that we could by no means he capable of perceiving it, our atmosphere is found to be so rare, at the height of 44 miles, as to be incapable of refracting the rays of light, the height is the 180th part of the earth’s diameter; but since clouds are never observed higher than four miles, we must conclude that the vaporous or obscure part is only 1980the. The mean apparent diameter of the moon is 31’ 29”, or 1889 seconds: therefore the obscure parts of her atmosphere, when viewed from the earth, must subtend an angle of less than one second; which space is passed over by the moon in less than two seconds of time. It could hardly therefore be expected, than the nicest observation should be adequate to determine, whether the supposed observation takes place or not.

3.The third argument is necessarily inconclusive, because we know not, whether there is any water in the moon or not; nor though this’ could be demonstrated, should it follow that the lunar atmosphere answers no other purpose than the raising of water into vapour. Farther, it may as well be doubted whether there is any solid matter, as fluid matter; for the presence of the one, argues the existence of the other ; nature furnishes no precedent, to justify the conclusion, that a solid body can exist, independent of a fluid state of that body all solids are concrete fluids, and all fluids are solids in solution, matter becomes solid by an abstraction of its menstruum, which being restored to it, reduces it to the fluid state; and being abstracted reduces it to the solid, besides, the admission of the doctrine, of the non-existence of a lunar atmosphere, or that of any other globe, would tend directly to destroy the doctrine of the law, and force of attraction; which, from reason and analogy, appears to be a stream, and supply, of all the elementary principles, and materials, of which a world is composed.

4.There is besides a strong argument in favour of the existence of a lunar atmosphere, taken from the appearance of a luminous ring round the moon in the time of solar eclipses ; a circumstance frequently observed by astronomers, particularly in the total eclipse of the sun in 1706; and in another total eclipse of the sun in April, 1715 When certain streaks of light were seen to dart from different places of the moon, during the time of total darkness, these were imagine to be flashes of lightning ; and hence the existence of clouds, and, vapours, and an atmosphere have been inferred. These flashes might be connected with such appearances, as Dr. Herschel, has with great probability, concluded to be volcanos, which has also been considered as a proof of the lunar atmosphere.

We have already observed, that the occultations of the fixed stars and planets, by the moon, in general happened without any kind of refraction of their light by the lunar atmosphere, the contrary, however, has sometimes, it is said, been observed, and the stars have been seen manifestly to change their shape and colour on going behind the moon’s disk ; but by many this colour has been attributed rather to the different refrangibility of the rays, in the object glass of the telescope, than to any real variation of colour in the planets and stars from appulse to the moon.

It is remarkable that the moon, during the week in which she is full about the time of harvest, rises sooner after sunsetting, than she does in any other full moon week throughout the year. By this means, she affords an immediate. supply of light after sunset, which is very beneficial for those employed in the harvest, and gathering the fruits of the earth. Hence this full moon is distinguished from all others in the year, by calling it the HARVEST-MOON.

To conceive the reason of this phenomenon, it may first be consider. ed, that the moon is always opposite to the sun when she is full, and therefore, in the harvest months, she is full in Pisces and Aries, which are opposite to Virgo and Libra, the signs occupied by the sun at the same season. Now, the signs Pisces and Aries rise in a shorter space of time than others, as is easily shown and illustrated by a celestial globe; and the same thing may be conceived from this circumstance, that in northern latitudes, the smallest angle, made by the ecliptic and the horizon, is when Aries rises at which time Libra sets ; and it is obvious, that the smaller the angle contained by the ecliptic and horizon, the greater portion of the ecliptic will rise by the earth’s rotation, in a given time. Consequently when the moon is full in harvest, she rises with less difference of time, or more immediately after sunset, than at any other season of the year.

In our winter, the moon is in Pisces and Aries, about the time of her first quarter, when she rises about noon, and therefore her rising is not then noticed.

In spring, the moon is in Pisces and Aries, about the time of her change, but she then gives no light, and rises with the sun, her rising cannot be perceived.

In summer the moon is in Pisces and Aries, at the time of her last quarter, and then she does not rise till midnight, her rising usually passes unobserved. .

But in Autumn the moon is in Pisces and Aries at the time of her full, and rises soon after sunset, for several evenings successively; which makes her regular risings very conspicuous, at that time of the

All this would happen, if the moon’s orbit lay in the ecliptic’; but her orbit makes with the ecliptic an angle of 50 18’, and crosses it in two points, called her nodes; so that her rising when in Pisces and Aries, will sometimes not differ above an hour and 40 minutes, through a whole week ; and at other times, in the same two signs, she will differ in a week 3 1/2 hours, in the times of her rising, according to the different positions of her nodes, with respect to these signs; which positions are always changing, because the nodes go backwards through the ecliptic, in 12 years 225 days.

This revolution of the nodes, causes the harvest-moons to go through a whole course of the most advantageous and least beneficial states, with respect to the harvest every 19 years. They are most beneficial at present, in 1816, and will continue so till 1825, when the opposite period commences, and lasts to 1834 ; and again they will be most beneficial from 1835, to 1843, and so on.

12, The TIDES are found to follow periodically the course of the sun and moon, and hence it has been suspected in all ages, that the tides were somehow produced by the influence of those luminaries. Of this Pliny, Ptolemy, Macrobius, and others seem to have some knowledge. The celebrated Kepler formed some conjectures long ago, as to the true cause of the tides. “If (says he)’ the earth ceased to attract the waters towards itself, all the waters in the ocean would rise and flow into the moon. The sphere of the moon’s attraction extends to our earth, and draws up the water.” What Kepler only surmised, has been successfully investigated by the great Newton, and Dr. Halley from his principles. The general phenomena of the tides are as follows:

1. The sea is observed to flow for about 6 hours, from south to north gradually swelling; and after a flux of about 6 hours, it seems to rest for a quarter of an hour ; and then to ebb, or retire back again from north to south for 6 hours more. Then, after a seeming pause of about a quarter of an hour more, the sea again begins to flow ; and so on alternately.

2. Hence, the sea ebbs and flows twice a day, but falling every day later and later, by about 48 minutes, the period of a flux and reflux being on an average about 12 hours 24’, and the double of each 24 hours 48’, which is the period of a lunar day, or the time between the moon’s passing a meridian and coming to it again, so that the sea flows as often as the moon passes the meridian, both the arch above the horizon and that below it, and ebbs as often as she passes the horizon, both on the eastern and western side. These are the most obvious appearances: the other phenomena as follows:

3. The elevation towards the moon exceeds the opposite one a lit. tie, and the quantity of the ascent of the water is diminished from the middle latitudes, towards the equator, and towards the poles.

4. The sun raises and depresses the sea twice every day, in the same manner as the moon does; but the solar tides are much less than the lunar one ; although subject to the same laws.

5 The tides which depend upon the actions of the sun and moon, are not distinguished, hut compounded; and thus they form to appearance, one united tide, which increasing and decreasing, produces ‘what are called NEAP and SPRING tides.

6. In the syzygies, the elevations from the action of both luminaries concur, and the sea is more elevated; but the sea ascends less in the quadratures ; for where the water is elevated by the action of the moon, it is depressed by that of the sun, and vice versa. There. fore while the moon passes from syzygy to the quadrature, the daily elevations are continually diminished; on the contrary, they are increased, while the moon passes from the quadrature to the syzygy. At the new moon also cateris paribus the elevations are greater; and those that follow one another the same day, are more different than those at full moon.

7. The greatest elevation and depression takes place on the 2d or 3d day after the new or full moon, and they are the greater, the nearer these luminaries are to the plane of the equator ; being greatest in the syzygies, near the equinoxes.

8. The actions of the sun and moon are greater, the nearer those bodies are to the earth; and the greatest tides happen, when the sun is a little to the south of the equator ; but this does not happen regularly every year, because some variation may arise from the situation of the moon’s orbit, and the distance of the syzygy from the equinox.

9. The mean force of the moon to move the fluids of our globe is to that of the sun nearly as 4 1/2 to 1; and therefore, if the action of the sun alone produces a tide of 2 feet, which it is said to do, then that of the moon will be 9 feet; from which it follows, that the spring tides will be 11 feet, and the neap tides 7 feet. But such elevations, as far exceed these, happen from the motion of the water against some obstacles, and from the sea violently entering straits, bays, or guts, where the force is riot broken till the water rises higher.

The preceding phenomena take place in the open sea, where the ocean is extended enough to be subject to those motions. But the particular situations of places, as to shores, capes, bays, &c. disturb in a considerable degree these general rules. We are now to show how these phenomena may be explained, from the principle of universal gravitation.

If the earth were -entirely fluid and quiescent, its particles, by their common gravitation to the centre would naturally form themselves into an exact sphere. If a power were to act on all the particles of this spheres with an equal force, and in parallel directions, the whole mass would be moved together, but no change would be produced on its spherical figure, and its centre would have the same motion as each particle.

Upon this hypothesis, if the motion of the earth, round the centre of gravity of the earth and moon, were destroyed, and the earth left to. the influence of its gravitation towards the moon, (and this independent of any repelling power) then the earth would fall or move straight towards the moon without changing its spherical figure.

But the fact is, that the effects of the moon’s action as well as the action itself, on different parts of the earth, are not equal; those parts, by- the general laws of gravity, being most attracted, that are nearest to the moon, and those least attracted which are farthest from her; while the parts at a middle distance, are attracted by a mean degree of force; besides, all the parts are not acted upon in parallel lines, but in lines directed to a centre, on which accounts, the spherical figure of the fluid earth. must suffer some change from the action of the moon, so that in falling, as we have supposed, the nearer parts being most attracted, would fall quickest, the farther parts being least attracted, would fall slowest, and the fluid mass would be lengthened out, and take a kind of spheroidical form, or rather a conical shape.

Hence it appears, (which must be carefully observed,) that it is not the action of the moon itself but the inequalities of that action, that cause any variations of the earth from a spherical figure; and that if this action were the same on all particles, as the central parts, and operating in the same direction, no such change would ensue.

Let- us now admit the parts of the earth to gravitate towards its centre; then, as this gravitation far exceeds the action of the moon, and much more exceeds the difference of her actions on different parts of the earth, the effect of which results from the inequalities of these actions of the moon, will be only a small dimunition of the gravity of those parts of the earth, which it endeavoured in the former supposition to separate from its centre; that is those parts of the earth which are nearest to the moon, and those that are farther from her, will have their gravity ‘towards the earth somewhat abated, to say nothing of the lateral parts; so that supposing the earth entirely fluid, the columns from the centre, to the nearest, and to the farthest parts must rise, till, by their greater height, they are able to balance the other columns, whose gravity is less abated by the inequalities of the moon’s action, and thus the figure of the earth must still be an oblong spheroid.

Let us now consider the earth, instead of falling towards the moon by its gravity, as projected in any direction, so as to move round the centre of gravity of the earth and moon, it is evident, that in this case the several parts of the fluid earth, will still preserve their relative position, and the figure of the earth will remain the same as if it fell freely towards the moon ; that is, the earth will still assume a spheroidical form, having its longest axis directed towards the moon.

From the preceding reasoning, it appears, that the parts of the earth directly under the moon, and also the opposite parts, will have the flood or high water at the same time, while the parts at 900 distance, or where the moon appears in the horizon, wilt then have the ebb or lowest water. Hence as the earth turns round its axis from the moon to the moon again in 24 hours 48’, this oval of waters must shift with it ; and thus there will be two tides of flood and two of ebb at that time. It farther appears, that by the motion of the earth on its axis, the most elevated parts of the waters are carried beyond the moon in the direction of the rotation ; so that the water continues to rise after it has passed directly under the moon, though the immediate action of the moon there begins to decrease; arid comes not to its greatest elevation till it has got about half a quadrant farther. It continues to descend after it has passed at 90 from the point below the moon, to a like distance of half a quadrant.

The greatest elevation, therefore, is not in the line drawn through the centres of the earth and moon, nor the lowest points, where the moon appears in the horizon, but all these are removed about half a quadrant eastward from these points in a direction of the motion of rotation. Thus in open seas, where the water flows freely. the moon is passed the meridian at high water in different distances, in proportion as she is near the syzygies, or quadratures; but in narrow seas, bays, and rivers, there is no rule, high water happening in such situations, according to the distances from the regular course of the tide. If the earth was subject to no other action than that of the moon, the distance of time, from the moon’s passing the meridian, till the time of high water, would be uniform; but this distance of time varies in proportion as the attractive force of the moon coincides with that of the sun. This coincidence takes place, when the moon is in her 1st and 3d quarters ; but the tides happen later in the 2d and 4th quarters; and the reason of this is obvious ‘for the waters are partly raised by the action of the sun, when the action of the moon begins to exert itself upon them.

In former remarks, we only adverted to the action of the moon, in producing the tides, but it is evident, that for the very same reasons, the inequality of the sun’s action, on different parts of the earth, would produce a like effect, and a like deviation from an exact spherical figure; so that in reality, there are two tides every natural day, from the action of the sun, as there are every lunar day from the action of the moon, subject to the same laws ; and the lunar tide is somewhat varied by the action of the sun, and this variation takes place. every day on account of the inequality between the natural and lunar day.

Notwithstanding the gravitation of the earth towards the sun, is much greater than its gravitation towards the moon ; yet by reason of the sun’s immense distance, to which the earth’s diameter bears but a small proportion, his action on the side of the earth next to him differs but little, from that, which is exerted on the side furthest from him, and it is only the inequalities in that action, which produces the solar tide : arid it should be recollected, that the earth and its satellite, the moon, gravitate together towards the sun, in one line of attraction; consequently the mutual gravitation of the earth and moon, will be in a just relation to their magnitudes and distances. However the effect of the sun is very distinctly sensible, though that of the moon is more perceptible; for by its proximity to the earth. there is a greater proportion of inequality, both in the direction of its action, and in the intensity of that action on different parts of the earth.

Hence it is easy to see that the tides must be greatest, at new and full moon, because the actions of the sun and moon are then exerted in the same directions. These are called SPRING TIDES ; whereas when the sun and moon are 90 distant, the action of the one luminary, raises the tides, just where that of the other depresses them; and thus are produced what are called TIDES. Newton has calculated these effects of the sun and moon respectively upon the tides from their attractive powers, the former he finds to be, to the force of gravity, as I to 12,868,200. And be concludes, that the force of the moon, is to that of the sun, as 44.815 to 1..

Dr.. Horsely, however, in his edition of Newton’s Principia, estimates the force of the moon to that of th sun, as 50,469 to I ; and other authors have given different proportions. But Newton computes, from his proportion that the moon may raise the waters 9 feet 1 1/3 inch, and the sun and moon together may produce an elevation of about 1 feet 3 inches, and about 12 1/4 feet, when the moon is at her nearest distance. Now this is found by observation, to he nearly the case, in the average occurrence of tide on the coasts of the open and deep ocean.

It must be observed, that the spring tides do not happen precisely at new and full moon. nor the neap tides precisely at the quarters, but a day or two after, because, as in Other cases, so in this, the effect is not greatest or least, when the immediate influence of the cause is greatest or least, for if the actions of the sun and moon were to cease, yet the titles would continue for some time; as the waves of the sea continue for some time after a storm.

The different distances of the moon from the earth, produce a sensible variation in the tides, and Newton has shown. that they increase, as the cubes of their distances decrease, so that the moon at half her distance, would produce a tide eight times greater. The moon describes a path round the earth, of an oval figure; and at her nearest distance, produces a tide sensibly greater than at her farthest distance. Hence two great spring tides never succeed each other, at the distance of 14 days, for if the moon be at her least distance at the change, and therefore produce a great spring tide, she will be at her greatest distance at the full, and therefore the spring tide will be less.

The spring tides are highest, and the neap tides lowest, about the time of the equinoxes, because, were the sun, or moon in the pole of the world, there would be no tide; for their action would raise the water at the equator, or any parallel, equally round the earth: therefore, the nearer they are to the equator, the greater will be their effect. When the sun and moon traverse the equator, the tides, which are under them, ivill traverse the greatest circle, and the waters will be put into the greatest agitation. They will also be the greater at these times, because the whole force of attraction, is concentrated on the equator, and exerted to either pole, about the middle of March, and September.

As the greatest of the two tides, happening in every diurnal revolution of the moon, is that in which the moon is nearest the zenith, or nadir, therefore, while the sun is in the northern signs, the greater of the two diurnal tides, in the northern regions, will be that arising from the moon, when above the horizon; and when the sun is in the southern signs, the greatest is that arising from the moon, when below the horizon. Thus, the evening tides in summer exceed the morning tides, and the morning tides in winter exceed the evening tides.

Such would the tides regularly be, if the earth were covered all over with the sea, to a great depth, so that the water might freely follow the influence of the sun and moon; hut, as the tides pass over shoals, and run through straights and bays of the sea, their motions become various, and their height in consequence, will depend on a great many circumstances. That the tides may have their free and full motion, the ocean in which they are produced, ought to be extended at least 90 from east to west; because that is the distance, between the greatest elevation, and the greatest depression, produced on the waters by the moon.

Hence it appears, that it is only in the great oceans, that such tides as we have described can be produced, and why in the larger Pacific ocean they exceed those in the Atlantic ocean.-Hence it may be considered as one reason why the tides are not so great in the torrid zone between Africa and America, where the ocean is narrower, as in the temperate zones on either side ; and why they are so small in islands at a great distance from the shores. It would likewise appear, that the waters cannot rise on one shore of the Atlantic ocean, without descending on the other, so that at the intermediate islands it must remain at a mean height, between its elevations on those two shores.

The tides, that enter the mouths of rivers from the ocean, are greatly retarded in their progress by the currents of the rivers. Mr. Condamine, while in South America, observed, that in the river Amazon, there were five high waters, and four intermediate low waters at once ; a similar circumstance takes place in the Hudson, in the Thames, and most long rivers.—The tide propagated in the German ocean, by the moon, when she is three hours past the meridian, takes twelve hours to reach London bridge, so, that when it is high water at the bridge, a new tide is already come to its height in the ocean, and in some intermediate place, it must be low water at the same time.

At several places, it is high water three hours before the moon comes to her meridian ; but that tide, which the moon pushes as it were before her, is only the tide opposite to, that, which was raised by her, when she was nine hours past the opposite meridian.

There are no sensible tides in the Baltic, the Mediterranean, or the Black seas ; for they communicate with the ocean, by such inlets, as are of such immense extent, that they cannot speedily receive, and empty water enough, to raise, and depress their surfaces sensibly. In the Caspian sea, the American lakes, &c. the moon’s attraction is nearly the same on all parts of their surface, so that no sensible swelling can take place in their waters.

We have already observed, that the immediate cause of the tide, was the force of attraction, exerted by the action of the sun and moon, on the fluid parts of our globe. But we have hitherto restricted our observations, to the effect of this force upon our waters : it now remains to take a more extended review of the effect of this force, upon our globe generally. Not only our waters, but the whole body of our earth, is amenable to the law which governs the tides ; even animals, and vegetables are subject to its operation, and there is unquestionably a kind of ebbing and flowing of the fluids, which enter into their composition; all the particles of our earth will be liable to be affected in proportion to their capacity of expansion. Our atmosphere, particularly, will be liable to be more affected by the power of this attractive law it consists of particles so attenuated, and capable of such extreme expansion, that it must be considered as a principal agent in the production of the phenomenon of the tides. If the pressure of our atmosphere were uniform, and undeviating, on the surface of the earth, and waters, no such thing as tide, could take place ; but, in consequence of its yielding texture, it conforms itself,.’ en masse, to all the impressions of attractive force ; and by its expansive, and condensive powers, it forms a due medium, between the attraction and repulsion of the earth to and from its centre. It has already been noticed, in the notes to Vol. I. page 450, that the force of attraction exerts itself ill direct lines, from the centre, to the circumference, and that the force is reciprocal, and proportional to the distance : that, in consequence of’ this rectilinear impulse, certain phenomena would naturally occur; the force of attraction is exerted on a point of the circumference of the globe, and passes through in a straight line, that in this line the greatest dilatations of the atmosphere take place, and consequently the greatest elevation of the waters, and this is what we call high tides. As the earth recedes from this point, and attains to 900 distant from it, it meets with a correspondent compression, its surface being parallel with the line of attraction, consequently, its waters will be proportionally depressed, and this we Call low tide. Could the earth remain a sufficient length of time in this situation, and the force of attraction continue to be exerted upon it, these points on the equatorial circumference, being rectangular to the line of attraction, would become flatted hike the poles; hence it would appear that the particular configuration of’ the globe, from a round to a spheroidal form, proceeded from two causes, viz, that of attraction, whereby its fluid parts are more immediately affected; and that of rotation, which gives spheroidity to its solid, and adhesive parts. Considering the expansive powers of our atmosphere, as a mean, whereby the earth is suspended in its orbit, at a proportionate distance from its centre of attraction, it would follow, as a natural consequence, that the bulk of our atmosphere, consists of such materials, as are capable of being compressed, and dilated beyond their equilibrium ; and that in the first instance, when it is exceedingly compressed, the centrifugal force will prevail, and it will fly off to a greater distance from the centre of gravity. On the other hand, should the atmosphere become exceedingly dilated, the centripetal force will prevail, and the earth will be impelled towards its centre of gravity, and will approach it, until it regains its equilibrium, or exceeds it, in proportion to the impetus it had acquired, when it will again he driven back, or farther from its centre of gravity, and so on alternately, approaching to, and receding from its centre, impelled by principles, and causes coexistent with itself, with which the all-wise Creator has invested all worlds, and which we call attraction. Hence it will be readily perceived, why the earth cannot approach nearer to, or recede farther from the sun, than a certain given distance; that it will consequently be preserved and retained in its orbit, at a mean proportionate distance from the sun; that the path which it describes round the ‘sun, will not be a circle, but a very eccentric ellipsis, projected in unequal curves ; and that all the particles of which it is composed will be perpetually, and uniformly responsive to its various evolutions.

It ought to be observed, that this general compression, and dilatation’ of the bulk of the atmosphere, which are effected by what are termed the solar and lunar attractions, are different from those local compressions and dilatations of the various strata of the atmosphere, whence originates storms, hurricanes, whirlwinds, &c. But it is a force which is exerted on the whole broad disk of the globe, producing at once, a dilatation in the apex, and so in a straight line, through the whole diameter of the globe, comprehending the atmosphere, and which produces the high tide; and a compression in the rectangles, of the earth’s diameter, which produces the low tide. The spring and neap tides, proceed from greater and less degrees of dilatation, and compression, occasioned by the different eccentric positions of the earth in its orbit.

We say the attraction of the sun, the attraction of the moon, &c. which expressions should be corrected, being apt to give an incorrect idea of the phenomenon; attraction being reciprocal between two globes, and in a ratio proportionate to their comparative diameters, magnitudes, and distances. Hence the true place of the sun is not in the centre of the system, but it revolves round the centre in common with the planets; nor is the earth the true centre of the moon’s orbit, but it describe an orbit with the moon, round the common centre.

Before the time of Kepler, astronomers supposed that the planets moved in circular orbits with uniform motions. But this justly celebrated astronomer, instead of taking for granted the truth of the hypothesis of his predecessors, applied himself with diligence to make observations on the heavenly bodies, and who, from his great accuracy and sagacity, has been considered as at the head of modern reformed astronomy. After much labour and many mistakes, he at last discovered the great laws of motion, which are hence called Kepler’s laws: They are as follows :—

1.The primary planets and comets describe round the sun, and the secondary planets describe round their respective primaries, areas proportional to the times.

2.The orbits described round the sun, and round the primary planets, are ellipses having the sun and the primary planets in the focus.

3.The squares, or the periodic times of planets revolving round common centres, are proportional to the cubes of their mean distances,

These laws were deduced by Kepler entirely from observation, and it is obvious, they are the very same which Sir Isaac Newton has investigated by geometrical reasoning, as the necessary consequence of a body revoking in an ellipse, by a force directed towards one of its foci.

We are therefore warranted to conclude that the planets are kept in their orbits by a force which is directed towards the sun ; that this force is reciprocal, and proportionate to their diameters that all the planets are suspended in equilibrium from their centres, and this, by virtue of their expansive forces that though the sun attracts the earth, the earth attracts the sun, but the sun has a superior attraction, inasmuch as he is of superior magnitude. Thus, our earth being of superior magnitude to the moon, it has an attraction proportionally superior to the moon ; hence the tides are raised more by its own attraction, than by that of the moon.

To a spectator placed in the sun, all the planets would appear to describe circles annually in the heavens : for though their motions are really elliptical, the eccentricity is so small, that the difference between them and true circles is not easily perceived even on earth; and at the sun, whether great or small, it would entirely vanish.— These circles which would be apparently described among the fixed stars, are called the heliocentric circles of the planets. To a spectator in the sun, the comets though moving inn the most eccentric orbits, would also appear to describe circles in the heavens : for though their orbits are in reality very long ellipses, the planes of them extended to the heavens, would mark a great circle, of which the eye would be the centre; only as the real motion is an ellipsis, the body would appear to move much more slowly in some parts of the circle than others, and to differ excessively in magnitude.

To an inhabitant of any planet, however, the sun appears to go round in its own heliocentric circle, or to describe in the heavens, that same curve, which the planet would appear to do if seen from the sun.

The heliocentric circle of the earth is called the ecliptic ; because eclipses of the sun or moon can only happen when the latter are in or near it.

Although the sun appears to go round the earth annually in this circle, we cannot determine his place by mere inspection, as we do that of any other of the heavenly bodies ; for the fixed stars are the only marks by which we can determine the place of any of the heavenly bodies ; and the superior brightness of the sun renders them totally invisible, except in the time of a great eclipse, when his light is for a time totally obscured. But though we cannot know the place of the sun directly, it is easily found from a knowledge of those fixed stars which are opposite to him.

The LATITUDE of any planet is either heliocentric, or geocentric

The heliocentric latitude is its distance from the ecliptic as seen from the sun, and its geocentric as seen from the earth. As the orbits of the planets are inclined in different angles to the ecliptic, the heliocentric latitude of any planet, is almost always different from its geocentric latitude.

The two points where the heliocentric of any planet cuts the ecliptic, are called its nodes ; that point where it cuts the ecliptic to pass into north latitude is called the ascending node, and that to the south, the descending node. A line drawn from one node to the other, is called, the line of nodes, which is the common section of the plane of the ecliptic, and that of the planet produced on each side to the fixed stars.

A motion in the heavens, in the order of the signs of the ecliptic, as through Aries, Taurus, Gemini, &c. is called a motion in consequence; such, are the true motions of all the planets, though sometimes their apparent motions are contrary, then they are said to move in antecedence. The local zodiac, is not always invariably the same, as to the places of the several signs, though the whole always takes up the same place in the heavens, viz. 10 on each side of the ecliptic. The points where the celestial equator cuts the ecliptic, are found to have a motion in antecedence of about 50 seconds a year.

This change of place of the first point of the ecliptic, from whence the signs are counted, occasions a like change in the signs themselves which, though scarcely sensible for a few years, has now become very considerable.

The LONGITUDE of a phenomenon in the heavens, is the number of degrees counted from the first point of Aries on the ecliptic, to the place, where a circle of latitude drawn through tine phenomenon would cut the ecliptic at right angles. Every phenomenon in the heavens, whether in the zodiac or not, is thus referred to the ecliptic, by its circle of latitude, or great circle passing through the phenomenon, and cutting the ecliptic at right angles; and whatever sign the circle of latitude passes through, the phenomenon is said to have its place in that sign, though ever so far distant from it.

The common way of reckoning the longitude of a phenomenon is to take v for the first point of the ecliptic, and not to number the degrees quite round that circle, as a continued series, but to make a new beginning at the first point of every sign, and to reckon from thence only the length of 30, then the phenomenon is stated to be in such a degree and minute of such a sign: thus, 13 40’; or Mercury in the ascending node in Taurus, and so of any other. A point in the heavens is expressed, by setting down its longitude and latitude.

Every planet like the moon, is sometimes in CONJUNCTION, sometimes in OPPOSITION with the sun. Its conjunction is when the geocentric place of the planet is the same with that of the sun; though an exact and central conjunction can only take place, when the of its nodes passes through the earth, and the planet itself is in one of its nodes at the time.. It is however, termed a conjunction when the same circle of latitude passes through the sun and planet at the same time. When the geocentric place of a planet is in 90, or a quarter of a circle from the sun’s place, it is said to be in quadrature or in a quartile aspect with the sun’; and these terms are use4 in a like sense when applied to any two of the heavenly bodies. Thus the sun moon, or the moon and any planets, or any two planets, may be in conjunction, opposition, or quadrature.

The inferior planets have two kinds of conjunctions with the sun one in the inferior part of their semicircles, the other in the superior part. In the former the planet is between the earth and the sun; the latter the sun is between the earth and planet. The. inferior planets can never be in opposition to the sun, nor even appear at a great distance from him. The length they go is called their elongation.

The greatest possible elongation of Mercury, or his aphelion distance, is found by astronomical observations, to be about 28 and that of Venus, about 48. The inferior planets in their elongations, are sometimes eastward and sometimes westward of the sun; in the: former case they appear in the evening, in the latter in the morning The smallness of Mercury, and his nearness to the sun, prevents him from being taken notice of; but the largeness and beauty of Venus, have made her ‘celebrated in all ages as the evening and morning star..,

The planets sometimes appear to go forward, sometimes to go backwards, and sometimes to stand still. These different conditions are by astronomers called direct, retrograde, and stationary. Were they to l)e viewed, from the sun, they would always appear direct; but, when viewed from the earth, the inferior planets appear direct while moving in their upper semicircles: retrograde while moving in their lower ones, and stationary while changing from direct to retrograde, or retrograde to direct.

When the earth is in the line of nodes of an inferior planet, the, apparent motion of the former is then in a straight line, because the plane of it passes through the eye: if in a conjunction in his upper. semicircle, he passes behind the sun, if in his lower semicircle, he. passes before it, and will then be seen by an observer on earth to pass over the sun’s disk like a round and very black spot. Were the plane of his orbit coincident with the ecliptic, this appearance would be seen. every year; but by reason of the obliquity of the two planes to each’. other it is much more rare.

MERCURY however was seen in this manner November 12th, 1782,. at3 hours 44’, in the afternoon; May 4th, 1786, at 6 hours 37’, in the morning; December 6th, 1789, at 3 hours 5’, in the afternoon. Is like manner VENUS sometimes appears like a black spot on the sun, but much more seldom than Mercury. She was thus seen first in 1639 afterward in the years 1761, and 1769; but will not again be visible in this manner till the year 1874.

An inferior planet, when in conjunction with the sun, in its inferior semicircle, is said to be in PERIGEE, and when in the other, to be in APOGEE, on account of its different distances from the earth. Their real distances from the earth when in perigee, are variable, partly owing to the eccentricities of their orbits, as well as that of the earth and partly owing to the different bodies by which they are in perigee, in different parts of their orbits. The least possible distance is, when the perigee happens at the time that the earth is in its perihelion and when the planet is in its aphelion.

The difference between the earth and inferior planets, at different times, makes a considerable variation at different times, which indeed is very observable in all the planets ; and thus, they sometimes look considerably larger than at others. This difference of magnitude in Mercury is nearly as 5 1/2 to one; and in Venus no less than 32 to I, any person unassisted by instruments, may observe an inferior planet alternately approach nearer and nearer the sun, until at last it comes into conjunction with him, and then retires farther and farther, till it is at its greatest elongation, which will be first on one side, and then on the other: but if we observe the apparent change of a place of an inferior planet, in the sphere of the heavens, its direct motions, stations and retrogradations, measuring its diameter ‘frequently with the mecrometer, we shall find, by its decrease at some times, and increase at others, that its distance from us is very considerably varied.

The apparent paths of Mercury and Venus are looped curves.

As the superior planets move in larger orbits than the earth, they can only be in conjunction with the sun, when they are on that side opposite to the earth; as on the other hand they are in opposition to him when the earth is between the sun and them. They are in quadrature with him, when the geocentric places are at 90 distance from the sun.

The DIRECT MOTION of a superior planet is swifter the nearer it is to a conjunction, and slower as it approaches to a quadrature with the sun.

The RETROGRADE MOTION of a superior planet, is swifter the nearer it is to an opposition, and slower as it approaches to a quadrature with the sun.

A superior planet is in APOGEE when in conjunction with the sun, and in PERIGEE when in opposition; and every one of the superior planets, is at its least possible distance from the earth, where it is in perigee and perihelion at the same time. Their apparent diameters are variable, according to their distances, like those of the inferior planets; and this as might naturally be expected, is most remarkable in the planet MARS, who is nearest us. In his nearest approach, this planet is 25 times larger than when farthest off, Jupiter twice and a half, and Saturn once and a half. As the times of conjunction, utmost elongation, direct or retrograde motion, of the inferior planets depend on the combinations of their motions in their orbits with the motion of the earth in its orbit; any of these appearances will h€ more frequent in Mercury than in Venus, because the former moves with a swifter motion in his orbit, and consequently, must more frequently pass through those places, where he is in conjunction, &c.

The time in which any of the inferior planets will return into a given situation, may be easily known. Compute the diurnal hello. centric motions of Venus and the earth: the difference of their motions, is the diurnal motion of Venus from the earth, or the quantity by which Venus would be seen to recede from the earth every day, by a spectator placed in the sun: thus the motion of Venus is every day about 59 minutes and 8 seconds; the difference is 37 minutes Therefore, as 37 minutes is to 360 degrees, or to 21,600 minutes, so is one day to the time wherein Venus, having left the earth, recedes from her 36O degrees; that is, to the time wherein she returns to the earth again, or the time between two conjunctions of the same kind.

The calculations of the times are here made according to mean or equable motions of the planets, and is therefore called a mean conjunction: but because Venus and the earth are really carried in elliptic orbits, in which their motions are sometimes swifter and sometimes slower, the true conjunctions may happen some days either sooner or later than what these rules will give. The time of the true conjunction is to be computed from that of the mean conjunction, in the following manner. Find by astronomical tables the place of Venus and the earth in the ecliptic, from which we shall have the distance of the two as seen from the sun ; compute also the angular motions of these two planets for any given time, suppose six hours. As this difference is to the arc between the places of Venus and the earth, at the time of a mean conjunction, so is six hours to the time between the mean conjunction and the true. This time added to, or subtracted from, the time of the mean conjunction, according as Venus is in antecedence or consequence from the earth, shows the time of the true conjunction.

As to the conjunctions, oppositions, direct, and retrograde motions, &c. of the superior planets, they depend on the combinations of their motions with that of the earth, and are more frequent in Saturn than in Jupiter, and in Jupiter than in Mars; but most frequent of all in Herschel; because the slower the motion of the planet is, the sooner the earth will overtake in so as to have it again in any given situation.

Thus suppose Saturn to be in conjunction with the sun in Aries, if he were to stand still one year, then he would again be in conjunction with the sun in Aries, but, as he goes on slowly, according to the order of the signs, about 12 degrees annually, the earth must therefore go through almost 13 degrees more than an entire revolution, so that there will be almost a year and 13 days, between any conjunction between the sun and Saturn, and the conjunction immediately following. As Jupiter moves in his orbit, with greater velocity than Saturn, the earth must have a proportionably larger space added to the year; and as Mars moves swifter still, the time between any two of his conjunctions, must be still longer. The time when any superior planet will return into any given situation, may be found by the methods already laid down for the inferior planets; and the true conjunctions, &c. may be found in the superior planets as in the inferior.

Here it is worth while to pause a few moments, and contemplate the immense scale of being, to consider the magnitudes, relations, order, and arrangement of those immense globes, which occupy the unlimited regions of space, and diffuse their lustre and beneficence around us. And,

1. None of them interfere with each other. Had the universe been the work of any but the wise Architect, there would have been many inconveniences in the situation of such a prodigious number of immense globes. Some would have been too near or too far off; some would have incommoded others. But instead of this, all the globes which fall under our notice, are set at such a due distance as not only to avoid all violent concourse, but not to shade each other, so as to hinder each others kindly influence, or to occasion noxious ones. 2. As it is one great instance of the skill of an architect, to give due proportion to his works, so this abundantly appears in all the heavenly bodies that come under our cognizance. Curious order, and due and nice proportions are observed in their situations. The sun is placed in the centre of his system, to give all his planets heat and light. Then follow the several planets surrounding him, not scattered at all adventures, but at due distances from the sun, as well as from one another. And this is discernible, not only in the primary, but the secondary planets too: in the five moons that attend Saturn, and the four that accompany Jupiter.

The wisdom of the Creator appears, secondly, from the motions of the heavens and the earth. That these vast globes should move at all, proves some being that has power to put them in motion: seeing matter cannot move itself. And suppose them moved by the sun, the ether, or some other primary mover, still we must recur to some first cause who was able to put the mover into motion. And this could be no other than the hand of the Almighty. What farther shows both his power and wisdom, is, that those motions are not at random, or in inconvenient lines and orbs, but such as manifest the deepest counsel. That every planet should have as many and various motions, as the world and its inhabitants have occasion for, must be the work of a wise and kind, as well as omnipotent Creator.

In particular, the diurnal motion of these globes shows the wisdom of the Creator. Of what prodigious use is this Were the planets always to stand still, half of each globe would be dazzled and parched with unceasing day, and the other half wrapt in everlasting darkness Were this the case with our globe, a great part of it at least would scarce be habitable. It would neither agree with the state of man or other animals, nor of vegetables. How could the vapours be raised to supply the earth with cooling clouds and fruitful showers ‘low could the winds be excited to fan the atmosphere with their pleasant and healthful gales How could vegetables be raised up by the kindly heat of the day, and tempered by the dews arid cool of the night How could men and other animals gather their food, and perform the various labours of the day, and then under the salutary influences of the night recruit themselves with rest and sleep -

And as the diurnal, so the annual motion of the heavenly bodies, is a clear manifestation of the Creator’s wisdom : especially when we consider the different paths of their diurnal and annual motions. These lie not in a very different plane, nor in the same, but a little crossing one another: the diurnal lying in or parallel to the equator: the annual, at an inclination of twenty-three degrees and a half A glorious contrivance this for the good of our globe, and for all the rest that have the same annual motion! For were the earth’s annual motion to be always in the same plane with the diurnal, we might indeed he sometimes nearer to the sun than we now are. But we should miss of those kindly increases of day and night, which the approach of the earth to one or the other pole occasions. This is likewise the great cause of summer and winter. Indeed one cause of them is, the longer or shorter continuance of the sun above the horizon. As it continues longer in summer, it increases the heat, as much as it lengthens the day : and just the contrary in winter. But the chief cause is, the oblique or perpendicular direction of the sun’s rays. For, 1. Perpendicular rays strike on any plane with greater force than oblique. And, 2. A greater number of rays fall within the same compass, in a perpendicular than in an oblique direction.

A farther manifestation of the Creator’s wisdom we have in the perpetuity. constancy and regularity of those motions. How without an Almighty guide should those vast bodies continue their course throughout all ages How should they perform their usual stages, without the least intermission or disorder What piece of clockwork under heaven, was ever comparable to this How steadily do all these motions conspire, to answer the ends of divine Providence, to despatch the noble offices of the several globes, to comfort amid cherish every thing residing on them, by the useful change of day and night, and the several seasons of the year!

We may learn the wisdom of Cod, thirdly, from the figure of the heavenly bodies, so well suited to the motions, and to the whole state and convenience of them. And, 1. They are all nearly spherical:

I say, nearly, to allow for their difference between their polar and equatorial diameter. Now this figure is both more capacious than any other, and more agreeable to a mass in motion, each part of it being at a due distance from the centre of motion and gravity: besides, without this, there could have been no such agreeable alterations of day and night, of heat and cold. And as to our own globe, the winds could not have fanned the air, as now, but must have been greatly retarded, if not wholly stopped, by the angles and jettings out of other figures. Lastly, the waters would have had intolerable confluences; here too much, there none at all. So that instead of habitable world, far the greatest part would have been a desert, or an useless bed of waters.

And all the parts of the earth are so distributed as may best minister to their several uses. Thus, the two grand parts, the solids and fluids, instead of being jumbled into one mass, are admirably parted, and as nicely disposed of in proper places. The strata conveying sweet water in all or most parts of the world, consist of proper, pervious matter, remain distinct from the other strata, and lie at such due depths, as either to break out in fountains, or to be dug into for wells: all of which is a manifest demonstration of the concern of a Wise Agent.

And not only the planets are a demonstration of this, but the very comets also: though their motions are so far from being always the same way, that they move sometimes contrary to each other. Their planes and directions lie every way, and their orbits are exceedingly eccentrical. But this very eccentricity is an admirable contrivance of the Creator, to prevent their disturbing either the planets, or one another, by mutual attractions. By this means they have sufficient room to revolve in; and by ascending to very great heights, and spending almost all their time in the remote regions of the universe, at vast distances both from the planets and each other, they incommode neither. Whereas had they moved in the same plane with the planets, they would sometimes have come too near them: and possibly have disturbed their motions, or even dashed against them.

But what would all the planets have done, had they not been sup. plied with light and heat And what an indulgent provision of these is made even for the most distant of them See the sun, that prodigious mass of elementary matter placed in the centre of the system, to scatter his light throughout the whole, and to warm and cherish us by day: and such a noble retinue of moons and stars, attending and assisting us by night! And we see the same care of the Creator, extended to all the other planets. According to their several distances, they have proportionably a great number of moons, and Saturn a stupendous ring besides, to supply the decrease of light and heat. Who can help being amazed at such well contrived, such stately works of God! Who can partake of their beneficial influences, and not adore the wisdom and kindness of their Maker!

That he who dispenses existence at his will, should multiply, extend, enlarge, and add a kind of immensity to his works, is not properly what surprises me; at least my amazement is chiefly founded on my own extreme littleness. But what astonishes me most is to see, that notwithstanding this, my extreme littleness, he has vouchsafed to regulate his immense works, by the advantages I was to receive from them!

The heavens declare the grandeur and glory of God, from one end of the world to the other. But the sun alone affects us more than all the beauties the heavens can display to our sight: the heavens are only a. pavilion to the sun. The richly embroidered veil which seemed to bide him from us for a season, is removed when he advances. At first, he appears as a young bridegroom, coming out of his chamber. His splendour is then full of mildness, and he is easy of access. But he is commissioned to convey the heat and the life, as well as the light, every where. He darts more and more fire as he ascends. He passes from one end of the heavens to the other. There is nothing can either be hid from his light, or subsist without his heat. And by his penetrating fires he reaches those very places which are inaccessible to his rays.

And yet we need his absence at proper intervals, no less than we do his presence. For night and sleep are so connected, that when we want repose, we generally procure a kind of artificial night. Our senses are seldom unbent, but by the removal of that which agitates them. And this is the service for which night is appointed, and which it excellently well performs. It does not come in a blunt and abrupt manner, to extinguish the light of the day, and all on a sudden to rob us of the sight of the objects we are intent on: but advances only by slow steps, and brings on darkness by degrees. It is not till after reminding us of the necessity of taking rest, that it covers the face of nature.

During the time of man’s repose, night hushes every noise. It indeed suffers a few animals, whose grim aspect might scare him, to go forth, and silently seek their food. It permits, however, the animal that stands center by him, to give him notice of what concerns him. But it keeps the horse, the ox, and all his domestics fast asleep around him. it disperses the birds, and sends each to his respective abode. As it comes on, it gradually hushes the winds, to secure the lord of nature’s rest. It causes his repose to be reverenced every where: the moment of which is no sooner come, but all creatures retire, and for several hours, an universal silence reigns.

Nor yet is nature’s palace wholly void of light. As some may be constrained to travel by night, several flambeaus are scattered through the firmament. But these, though they prevent total darkness, yield only a gentle light. Nor ought those who then wake to be supplied with such alight, as would interrupt the repose of others.

But it is not, by its darkness only, that night is useful to us. Its coolness likewise is of use: and this increasing the spring of the air, makes it capable of working with greater activity, and giving new vigour both to the dry plants and the enfeebled animals. It is to preserve this cool, that the moon reflecting the light of the sun, gives it without any sensible heat. In vain do we collect her rays by the strongest burning glass. An admirable caution of the Divine Artificer, who has reserved for the night season, a light strong enough to remove darkness, yet too weak to alter the coolness of the air.

When man is inclined to have the benefit of this, he sees no more the prospects of the day; but night in her turn, favours him with another, that has charms to itself.

We cannot doubt but these immense globes of fire, which enlighten our night, have all their peculiar appointments, which answer, in God’s purposes, the magnificence of their appearance. But who shall presume to explain, what the Almighty has thought fit to conceal The small glimpses which a few are permitted to have, being quite unknown to the bulk of mankind. It is not in the particular destination of each star, nor in the general harmony of all, that we are to look for the means of instructing man, or regulating his affections. But yet what we do see, and know concerning them, is matter for the deepest admiration. We see innumerable fires hung up in the magnificent ceiling of our abode; and the dark azure which serves them as a ground, still heightens their beauty and brightness. But their rays are dispersed through spaces so immense, that when they come to us, they are quite destitute of heat. Thus by the Creator’s providence we enjoy the sight of a multititude of fiery globes, without any danger of destroying the coolness of our night, or the quiet of our repose.

The sum of what has been said, with some farther improvements, we add in the words of Mr. Hervey.

“ The earth is, in fact, a round body, though in some parts raised into hills, or sunk into vallies, in others spread out into wide ‘and immeasurable plains. For the loftiest mountains bear no more proportion to the whole surface of the ball, than a particle of dust on the astronomer’s globe, bears to its whole circumference. We may fancy that it has deep foundations, and rests on some solid basis. But it is pendant in the wide transparent ether, without any visible support either from above or beneath. It may seem to remain still and motionless: but it is continually sailing through the depths of the sky, and in the space of twelve months finishes the mighty voyage. This periodical rotation produces the seasons, and completes the year. And all the time it proceeds in its annual circle, it spins upon its own centre, and turns ‘its sides alternately to the great fountain of light. By this means the day dawns in one hemisphere, while the night succeeds in the other. Without this expedient, one part of its regions would, during half the great revolution, be scorched with excessive heat, and languish under an uninterrupted glare: while the other would be frozen to ice, and buried under dismal and destructive darkness.

“ The earth in the revolution which it performs daily on its own axis, whirls about at the rate of above a thousand miles an hour. What an amazing force must be requisite to protrude so vast a globe, and wheel it on, loaded with huge rocks and mountains, with such a prodigious degree of rapidity!

“ Mean time the sun which seems to perform its daily stages, is fixed and immoveable. It is the great axle of heaven, about which the earth and many larger orbs wheel their stated courses. And small as it seems, it is far larger than the earth : Sir Isaac Newton supposes, 900,000 times. Are we ready to cry out, how mighty is the Being who kindled such a prodigious fire! And keeps alive from age to age, such an enormous mass of flame! And yet this sun, with all its attendant planets, are but a very small part of that grand machine, the universe. Every star is really a vast globe, like the sun in size and in glory. Nay, every star, as some suppose, is not merely a world, but the centre of a magnificent system; has a retinue of worlds enlightened by its beams, and revolving round its orb: all which are lost to our sight, in immeasurable wilds of ether.

“But could you soar farther yet, could you wing your way to the highest apparent star, you would there see other skies expanded, another sun distributing his beams by day, with other stars, that gild the horrors of the alternate night: and other, perhaps nobler, systems established, through the boundless dimensions of space. Nor does the dominion of the great Sovereign, terminate even here. Even at the end of this vast tour, you would find yourself advanced no farther than the suburbs of creation: arrived only at the frontiers of the great Jehovah’s kingdom

“Think on this. When innumerable bodies, many of them more than a hundred thousand miles in diameter, are set in motion: when the orbits in which they move are extended to hundreds of millions of miles: when each has a distinct and separate spheres for finishing his vast circuit; when none is cramped, but each freely expatiates in his unbounded career: when every one is so immensely distant from the others, that they appear each to other as only so many spots of light: how astonishing is the expanse which yields room for them all, and their widely diffused operations! To what lengths did the Almighty Builder stretch his line, when he marked out the stupendous platform! I wonder at such an immeasurable extent: my. thoughts are lost in this abyss of space.

“To go one step farther still: when I contemplate those ample and amazing structures, erected in endless magnificence, over all the etherial plains: when I look on them as so many repositories of light, or fruitful abodes of life : when I remember, there are orbs vastly more remote than those which appear to our unaided sight; when I stretch my thoughts to the innumerable orders of beings, which inhabit all those spacious systems, from the highest seraph to the puny nations that tinge the plume with blue, or mantle the standing poor with green. How various are the links in this immense chain, the gradations in this universal scale of existence ! Yet all these are the work of God’s hand, and are full of his presence!

“He rounded in his palm those dreadfully large globes, which are pendulous in the vault of heaven. He kindled those astonishingly bright fires, which fill the firmament with a flood of glory. By him they are suspended in fluid ether, arid never can be shaken; by him they dispense a perpetual tide of beams, and never are exhausted.— He formed that exquisitely tine collection of tubes, that unknown multiplicity of subtle springs, which organize and actuate the frame of the minutest insect, lie bids the crimson current roll, the vital movements play, and joins together a world of wonders, even in an animated point. For there are living creatures abundantly smaller than a mite. Mr. Bradly mentions some, which by computation he found to be a thousand times less than the least visible grain of sand; at the same time he declares, that this was a bulky beinz, compared to others discovered by Mr. Lewenhock. If then we consider the several limbs. which compose such an organized particle: the different springs which actuate those limbs; the flow of spirits which put those springs in motion; the various fluids which circulate: the different secretions which must necessarily be performed; together with the proportion-able minuteness of the solids, before they arrive at their full growth: we shall see the utmost reason to own, that the Creator is greatly glorious even in his smallest works.

“ To conclude this head. If the stars are magazines of fire, and immense reservoirs of light, undoubtedly they have some grand uses, suited to the magnificence of their nature. To determine what Uses, is not possible, in our present state of distance and ignorance. This however is clear, they are disposed in such a manner, as is most pleasing and serviceable to mankind. They are not placed at such an infinite remove, as to lie beyond our sight neither are they brought so near to our abode, as to annoy us with their beams.”