(see Astronomy Index, Encycl.) is certainly that celestial body which, of all others, should most attract our attention. It has accordingly employed much

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(a) Although lime is one of the constituent principles of the sulphuret, yet being so intimately united to the sulphur, it has no longer the property of lime; upon the same principle that sulphuric acid in sulphat of potash has not the property of that acid. Sir Isaac Newton has shown, that the sun, by its attractive power, retains the planets of our system in their orbits; he has also pointed out the method whereby the quantity of matter which it contains may be accurately determined. Dr Bradley has assigned the velocity of the solar light with a degree of precision exceeding our utmost expectation. Galileo, Scheiner, Hevelius, Cassini, and others, have ascertained the rotation of the sun upon its axis, and determined the position of its equator. By means of the transit of Venus over the disk of the sun, our mathematicians have calculated its distance from the earth, its real diameter and magnitude, the density of the matter of which it is composed, and the fall of heavy bodies on its surface. We have therefore a very clear notion of the vast importance and powerful influence of the sun on its planetary system; but with regard to its internal construction, we are yet extremely ignorant. Many ingenious conjectures have indeed been formed on the subject; a few of which we shall mention as an introduction to Dr Herschel's, of which, as it is the latest, and perhaps the most plausible, we shall give a pretty full account nearly in his own words.

The dark spots in the sun, for instance, have been supposed to be solid bodies revolving very near its surface. They have been conjectured to be the smoke of volcanoes, or the foam floating upon an ocean of fluid matter. They have also been taken for clouds. They were explained to be opaque masses swimming on the fluid matter of the sun, dipping down occasionally. It has been supposed that a fiery liquid surrounded the sun, and that by its ebbing and flowing the highest parts of it were occasionally uncovered, and appeared under the shape of dark spots; and that by the return of the fiery liquid, they were again covered, and in that manner successively assumed different phases. The sun itself has been called a globe of fire, though perhaps metaphorically. The waste it would undergo by a gradual consumption, on the supposition of its being ignited, has been ingeniously calculated; and in the same point of view its immense power of heating the bodies of such comets as draw very near to it has been assigned.

In the year 1779 there was a spot on the sun which was large enough to be seen with the naked eye. By a view of it with a seven feet reflector, charged with a very high power, it appeared to be divided into two parts. The largest of the two, on the 16th of April, measured 1'8"56 in diameter, which is equal in length to more than 31,000 miles. Both together must certainly have extended above 50,000. The idea of its being occasioned by a volcanic explosion violently driving away a fiery fluid, ought to be rejected (says Dr Herschel) on many accounts. "To mention only one, the great extent of the spot is very unfavourable to such a supposition. Indeed a much less violent and less perilous cause may account for all the appearances of the spot. When we see a dark belt near the equator of the planet Jupiter, we do not recur to earthquakes and volcanoes for its origin. An atmosphere, with its natural changes, will explain such belts. Our spot on the sun may be accounted for on the same principles. The earth is surrounded by an atmosphere composed of various elastic fluids. The sun also has its atmosphere; and if some of the fluids which enter into its composition should be of a shining brilliancy, in the manner that will be explained hereafter, while others are merely transparent, any temporary cause which may remove the lucid fluid will permit us to see the body of the sun through the transparent ones. If an observer were placed on the moon, he would see the solid body of the earth only in those places where the transparent fluids of our atmosphere would permit him. In others, the opaque vapors would reflect the light of the sun without permitting his view to penetrate to the surface of our globe. He would probably also find, that our planet had occasionally long shining fluids in its atmosphere; as, not unlikely, some of our northern lights might not escape his notice, if they happened in the unenlightened part of the earth, and were seen by him in his long dark night. Nay, we have pretty good reason to believe, that probably all the planets emit light in some degree; for the illumination which remains on the moon in a total eclipse cannot be entirely ascribed to the light which may reach it by the refraction of the earth's atmosphere. For instance, in the eclipse of the moon October 22, 1799, the rays of the sun refracted by the atmosphere of the earth towards the moon, admitting the mean horizontal refraction to be 30°50'8", would meet in a focus 189,000 miles beyond the moon; so that consequently there could be no illumination from rays refracted by our atmosphere. It is, however, not improbable, that about the polar regions of the earth there may be refraction enough to bring some of the solar rays to a shorter focus. The distance of the moon at the time of the eclipse would require a refraction of 54°6", equal to its horizontal parallax at that time, to bring them to a focus so as to throw light on the moon.

The unenlightened part of the planet Venus has also been seen by different persons; and not having a satellite, those regions that are turned from the sun cannot possibly shine by a borrowed light; so that this faint illumination must denote some phosphoric quality of the atmosphere of Venus.

In the instance of the large spot on the sun already mentioned, Dr Herschel concludes, from appearances, that he viewed the real body of the sun itself; of which we rarely see more than its shining atmosphere. In the year 1783 he observed a fine large spot, and followed it up to the edge of the sun's limb. Here he took notice that the spot was plainly depressed below the surface of the sun, and that it had very broad shelving sides. He also suspected some part, at least, of the shelving sides to be elevated above the surface of the sun; and observed that, contrary to what usually happens, the margin of that side of the spot which was farther from the limb was the broadest.

The luminous shelving side of a spot may be explained by a gentle and gradual removal of the shining fluid, which permits us to see the globe of the sun. As to the uncommon appearance of the broadest margin being on that side of the spot which was farthest from the limb when the spot came near the edge of it, we may surmise that the sun has inequalities on its surface, which may possibly be the cause of it. For when mountainous countries are exposed, if it should chance that the highest parts of the landscape are situated so as to be near that side of the margin or penumbra of the spot which is towards the limb, they may partly intercept our view of it when the spot is seen very obliquely. This would require elevations at least five or six hundred miles high; but considering the great attraction exerted by the sun upon bodies at its surface, and the slow revolution it has upon its axis, we may readily admit inequalities to that amount. From the centrifugal force at the sun's equator, and the weight of bodies at its surface, he computes, that the power of throwing down a mountain by the exertion of the former, balanced by the superior force of keeping it in its place of the latter, is near 6½ times less on the sun than on our equatorial regions; and as an elevation similar to one of three miles on the earth would not be less than 384 miles on the sun, there can be no doubt but that a mountain much higher would stand very firmly. The little density of the solar body seems also to be in favour of the height of its mountains; for, *exteris paribus*, dense bodies will sooner come to their level than rare ones. The difference in the vanishing of the shining side, instead of explaining it by mountains, may also, and perhaps more satisfactorily, be accounted for from the real difference of the extent, the arrangement, the height, and the intensity of the shining fluid, added to the occasional changes that may happen in these particulars during the time in which the spot approaches to the edge of the disk. However, by admitting large mountains on the face of the sun, we shall account for the different opinions of two eminent astronomers; one of whom believed the spots depressed below the surface of the sun, while the other believed them elevated above it. For it is not impossible that some of the solar mountains may be high enough occasionally to project above the shining elastic fluid, when, by some agitation or other cause, it is not of the usual height; and this opinion is much strengthened by the return of some remarkable spots which served Cassini to ascertain the period of the sun's rotation. A very high country, or chain of mountains, may often become visible, by the removal of the obstructing fluid, than the lower regions, on account of its not being so deeply covered with it.

In 1791 the Doctor examined a large spot on the sun, and found it evidently depressed below the level of the surface. In 1792 he examined the sun with several powers from 90 to 500, when it appeared evidently, that the black spots are the opaque ground, or body of the sun; and that the luminous part is an atmosphere, which, being interrupted or broken, gives us a transient glimpse of the sun itself. He perceived likewise, that the shining surface of the sun is unequal, many parts of it being elevated and others depressed; and that the elevations, to which Hevelius gave the name of faculae, so far from resembling torches, were rather like the shrivelled elevations upon a dried apple, extended in length, and most of them joined together, making waves or waving lines. The faculae being elevations, very satisfactorily explains the reason why they disappear towards the middle of the sun, and reappear on the other margin; for about the place where we lose them, they begin to be edgewise to our view; and if between the faculae should lie dark spots, they will most frequently break out in the middle of the sun, because they are no longer covered by the side-views of these faculae.

The Doctor gives a very particular account of all his observations, which seem to have been accurately made, and we need scarcely add with excellent telescopes; for that account, however, we must refer to the memoir itself, and hasten to lay before our readers the result of his observations. "That the sun (says he) has a very extensive atmosphere, cannot be doubted; and that this atmosphere consists of various elastic fluids, that are more or less lucid and transparent, and of which the lucid one is that which furnishes us with light, seems also to be fully established by all the phenomena of its spots, of the faculae, and of the lucid surface itself. There is no kind of variety in these appearances but what may be accounted for with the greatest facility, from the continual agitation which, we may easily conceive, must take place in the regions of such extensive elastic fluids.

"It will be necessary, however, to be a little more particular as to the manner in which I suppose the lucid fluid of the sun to be generated in its atmosphere. An analogy that may be drawn from the generation of clouds in our own atmosphere, seems to be a very proper one, and full of instruction. Our clouds are probably decompositions of some of the elastic fluids of the atmosphere itself, when such natural causes, as in this grand chemical laboratory are generally at work, act upon them; we may therefore admit, that in the very extensive atmosphere of the sun, from causes of the same nature, similar phenomena will take place; but with this difference, that the continual and very extensive decompositions of the elastic fluids of the sun are of a phosphoric nature, and attended with lucid appearances, by giving out light.

"If it should be objected, that such violent and unremitting decompositions would exhaust the sun, we may recur again to our analogy, which will furnish us with the following reflections. The extent of our own atmosphere, we see, is still preserved, notwithstanding the copious decompositions of its fluids in clouds and falling rain; in flashes of lightning, in meteors, and other luminous phenomena; because there are fresh supplies of elastic vapours continually ascending to make good the waste occasioned by those decompositions. But it may be urged, that the case with the decomposition of the elastic fluids in the solar atmosphere would be very different, since light is emitted, and does not return to the sun, as clouds do to the earth when they descend in showers of rain. To which I answer, that, in the decomposition of phosphoric fluids, every other ingredient but light may also return to the body of the sun. And that the emission of light must waste the sun, is not a difficulty that can be opposed to our hypothesis: for as it is an evident fact, that the sun does emit light, the same objection, if it could be one, would equally militate against every other affigable way to account for the phenomenon.

"There are, moreover, considerations that may lessen the pressure of this alleged difficulty. We know the exceeding subtilty of light to be such, that in ages of time its emanation from the sun cannot very sensibly lessen the size of this great body. To this may be added, that very possibly there may always be ways of restoration to compensate for what is lost by the emis- fion of light, though the manner in which this can be brought about should not appear to us. Many of the operations of Nature are carried on in her great laboratory which we cannot comprehend; but now and then we see some of the tools with which she is at work. We need not wonder that their construction should be so singular as to induce us to confess our ignorance of the method of employing them; but we may well assured that they are not a mere *infar natura*. Here he alludes to the great number of small telescopie comets; which he supposes, as others had done before him, may be employed to restore to the sun what had been lost by the emission of light. "My hypothesis, however, (continues he) does not lay me under any obligation to explain how the sun can sustain the waste of light, nor to shew that it will sustain it for ever; and I should also remark that, as in the analogy of generating clouds, I merely allude to their production as owing to a decomposition of some of the elastic fluids of our atmosphere, that analogy, which firmly rests upon the fact, will not be less to my purpose, to whatever cause these clouds may owe their origin. It is the same with the lucid clouds, if I may call them, of the sun. They plainly exist, because we see them; the manner of their being generated may remain an hypothesis—and mine, till a better can be propofed, may stand good; but whether it does or not, the consequences I am going to draw from what has been said will not be affected by it."

Before he proceeds to draw these consequences, he informs us that, according to the above theory, a dark spot in the sun is a place in its atmosphere, which happens to be free from luminous decompositions; that faules are, on the contrary, more copious mixtures of such fluids as decompose each other; and that the regions, in which the luminous solar clouds are formed, adding thereto the elevation of the faules, cannot be less than 1843, nor much more than 2765 miles in depth. It is true, continues he, that in our atmosphere the extent of the clouds is limited to a very narrow compass; but we ought rather to compare the solar ones to the luminous decompositions which take place in our aurora borealis, or luminous arches, which extend much farther than the cloudy regions. The density of the luminous solar clouds, though very great, may not be exceedingly more so than that of our aurora borealis.

For if we consider what would be the brilliancy of a space two or three thousand miles deep, filled with such corrugations as we see now and then in our atmosphere, their apparent intensity, when viewed at the distance of the sun, might not be much inferior to that of the lucid solar fluid.

From the luminous atmosphere of the sun, he proceeds to its opaque body; which, by calculation from the power it exerts upon the planets, we know to be of great solidity; and from the phenomena of the dark spots, many of which, probably on account of their high situations, have been repeatedly seen, and otherwise denote inequalities in their level, we surmise that its surface is diversified with mountains and valleys.

What has been said, enables us to come to some very important conclusions, by remarking, that this way of considering the sun and its atmosphere removes the great dissimilarity we have hitherto been used to find between its condition and that of the rest of the great bodies of the solar system.

The sun, viewed in this light, appears to be nothing else than a very eminent, large, and lucid planet, evidently the first, or, in strictness of speaking, the only primary one of our system, all others being truly secondary to it. Its similarity to the other globes of the solar system with regard to its solidity, its atmosphere, and its diversified surface, the rotation upon its axis, and the fall of heavy bodies, leads us on to suppose that it is most probably also inhabited, like the rest of the planets, by beings whose organs are adapted to the peculiar circumstances of that vast globe.

It may, however, not be unfit to remove a certain difficulty, which arises from the effect of the sun's rays upon our globe. The heat which is here, at the distance of 95 millions of miles, produced by these rays, is so considerable, that it may be objected, that the surface of the globe of the sun itself must be scorched up beyond all conception.

This may be very substantially answered by many proofs drawn from natural philosophy, which shew that heat is produced by the sun's rays only when they act upon a calorific medium; they are the cause of the production of heat, by uniting with the matter of fire which is contained in the substances that are heated; as the collision of flint and steel will inflame a magazine of gunpowder, by putting all the latent fire it contains into action. But an instance or two of the manner in which the solar rays produce their effect, will bring this home to our most common experience.

On the tops of mountains of a sufficient height, at an altitude where clouds can very seldom reach to shelter them from the direct rays of the sun, we always find regions of ice and snow. Now if the solar rays themselves convey all the heat we find on this globe, it ought to be hottest where their course is least interrupted. Again, our aeronauts all confirm the coldness of the upper regions of the atmosphere; and since, therefore, even on our earth, the heat of any situation depends upon the aptness of the medium to yield to the impression of the solar rays, we have only to admit, that on the sun itself, the elastic fluids composing its atmosphere, and the matter on its surface, are of such a nature as not to be capable of any executive affection from its own rays: and indeed this seems to be proved by the copious emission of them; for if the elastic fluids of the atmosphere, or the matter contained on the surface of the sun, were of such a nature as to admit of an easy chemical combination with its rays, their emission would be much impeded.

Our author then proceeds to support his theory by analogical reasonings; but as these will occur to such of our readers as are conversant with these speculations of astronomers, we pass on to his reflections upon the consequences of this theory. "That the stars are suns can hardly admit of a doubt. Their immense distance would perfectly exclude them from our view, if the light they send us were not of the solar kind. Besides, the analogy may be traced much farther. The sun turns on its axis; so does the star Algol; so do the stars called Lyre, Cephei, Antinori, Ceti, and many more; most probably all. From what other cause can we probably account for their periodical changes? Again, our sun has spots on its surface; so has the star Algol, and so have the stars already named, and probably every star in the heavens. On our sun these spots are changeable; so they are on the star Ceti, as evidently appears from the irregularity of its changeable luster, which is often broken upon by accidental changes while the general period continues unaltered. The same little deviations have been observed in other periodical flares, and ought to be ascribed to the same cause. But if flares are suns, and suns are habitable, we see at once what an extensive field for animation opens itself to our view.

"It is true, that analogy may induce us to conclude, that since flares appear to be suns, and suns, according to the common opinion, are bodies that serve to enlighten, warm, and sustain a system of planets, we may have an idea of numberless globes that serve for the habitation of living creatures. But if these flares themselves are primary planets, we may see some thousands of them with our own eyes, and millions by the help of telescopes, when at the same time the same analogical reasoning still remains in full force with regard to the planets which these flares may support."

The Doctor then observes, that from other considerations, the idea of flares or flares being merely the supporters of systems of planets, is not absolutely to be admitted as a general one. "Among the great number of very compressed clusters of flares I have given (says he) in my catalogues, there are some which open a different view of the heavens to us. The flares in them are so very close together, that, notwithstanding the great distance at which we may suppose the cluster itself to be, it will hardly be possible to assign any sufficient mutual distance to the flares composing the cluster, to leave room for crowding in those planets, for whose support these flares have been, or might be, supposed to exist. It should seem, therefore, highly probable, that they exist for themselves; and are, in fact, only very capital, lucid, primary planets, connected together in one great system of mutual support.

"The same remark may be made with regard to the number of very close double flares, whose apparent diameters being alike, and not very small, do not indicate any very great mutual distance: from which, however, must be deducted all those where the different distances may be compensated by the real difference in their respective magnitudes.

"To what has been said may be added, that, in some parts of the milky way, where yet the flares are not very small, they are so crowded, that in the year 1792, Aug. 22, I found by the gauges that, in 41 minutes of time, no less than 258,000 of them had passed through the field of view of my telescope.

"It seems, therefore, upon the whole, not improbable, that in many cases flares are united in such close systems as not to leave much room for the orbits of planets or comets; and that consequently, upon this account also, many flares, unless we would make them mere useless brilliant points, may themselves be lucid planets, perhaps unattended by satellites."

What a magnificent idea does this theory give of the universe, and of the goodness, as well as power, of its Author? And how cold must be that heart, and clouded that understanding, who, after the contemplation of it, can for one moment listen to the atheistical doctrines of those men who presume to account for all the phenomena of nature by chemical affinities and mechanical attraction? The man who, even in his heart, can say, that such an immense system, differing so widely in the structure of the different parts of it, but everywhere crowded with life, is the effect of unintelligent agency, is indeed, to use the emphatic language of an ancient astronomer—a fool.