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Dr. Brewster recurs in another place to this hypothesis to explain a circumstance, which we have not noticed, namely, that two of the new planets have very extensive atmospheres, while the other two have apparently none. He admits, that this is a difficulty not easily accounted for upon the supposition that they were once united. He takes occasion, therefore, from a comet passing somewhere near the region of the paths of these bodies, about the year 1770, to furnish the extra quantities of this fluid. This reminds us of the romantick days of Whiston.

For our own parts, we are perfectly ready to receive these celestial guests, and as many more as may present themselves, as bona fide planets and intitled to all the consideration and respect, which we pay to our older associates, and so far from marring the beauty and order of this association, to which we belong, we think that they add to it by adding to its variety. It was once thought that the planets could not exceed seven in number, either because there are seven stars in a remarkable cluster, or because there are seven musical divisions in the octave, or for some other reason about as good. The discovery of the planet Hershel produced almost as great a derangement as that of the smaller planets. It was another exception to the gradation of magnitude following the increase of distance. It was an interruption to the law of specifick gravities decreasing with the distances. Its satellites were found, in violation of all analogy, to have their orbits nearly perpendicular to the ecliptick, and what was still worse, they performed their motions contrary to the order of the signs. We begin to be reconciled to these apparent anomalies, and future discoveries may erect them into rules. All this proceeds from our notions of what is orderly, harmonious and fit, being derived from our limited knowledge, from a little narrow system in our own minds, which every new discovery requires to be altered and re-adjusted, or to be taken entirely to pieces and made over again; and it is not the least of the advantages of the study of Astronomy, that in so many instances it exposes our partial views and lurking prejudices. The discipline has an influence beyond the sphere in which it is received. We bring a more liberal mind to other inquiries.

There is another speculation, in which Dr. Brewster maintains that the sun is not inhabited, as some have been led to suppose from the observations of Dr. Herschel, which indicate an atmosphere and strata of dark and luminous clouds elevat

ed far above his surface. One of the reasons, which he gives, is, that the inhabitants would be precluded from the study of Astronomy; and another is, that the sun is an exception to the law of specifick gravities, forgetting, that these specifick gravities have been certainly determined only with respect to those planets that have satellites. We are not disposed to enter into a discussion of this question, believing, as we do, that we have not the materials for forming any satisfactory conclusion on the subject.

We shall give a few extracts as specimens of Dr. Frewster's manner, when his aim is merely to instruct. His style forms a striking contrast to that of Mr. Ferguson.

It appears, that the lunar surface is not only diversified with rocks and cavities, but that some parts of it are distinguished from others by their superiour illumination. The dark parts of the Moon's disc are always smooth, and apparently level; while the luminous portions are elevated tracts, which either rise into high mountains, or sink into deep and extensive cavities. The general smoothness of the obscure regions naturally induced astronomers to believe that they were immense collections of water. The names given by Hevelius are founded on this opinion; and notwithstanding the discoveries which have been made on the surface of the Moon, it is still very generally maintained among modern astronomers. When we examine the Moon's disc, however, with minute attention, we find that these obscure portions are not exactly level like a fluid surface. In many of them the inequality of surface and of light is considerable; and in some parts, parallel ridges are distinctly visible. The large dark spot on the Moon's western limb, which is called the Crisian Sea, appears in general to be extremely level; but we have frequently observed, when the Moon was a little past her opposition, and when the boundary of light and darkness passed through the Crisian Sea, that this bounding line, instead of being elliptical, as it would have been had the surface been fluid, was irregular, and evidently indicated that this portion of the Moon's disc was actually elevated in the middle. The light of these obscure regions, likewise, varies very much, according to the angle of illumination, or the altitude of the Sun above their horizon; and when the Moon is near her conjunction, they are not much less luminous than the other parts of her disc. Now this could never happen if they were covered with water ; for when a fluid surface is not ruffled by the wind, the light of the Sun, or rather the image of the Sun could not be seen, unless when the eye of the observer was in the line of the reflected rays.

It would appear, therefore, from these facts, that there is no water in the moon, neither rivers, nor lakes, nor seas, and hence we are entitled to infer, that none of those atmostpherical phenomena, which arise from the existence of water in our own globe, will take place in the lunar world.

The strata of mountains, and the insulated hills which mark the disc of this luminary have evidently no analogy with those in our own globe. Her mountainous scenery, however, bears a stronger resemblance to the towering sublimity, and the terrific ruggedness of Alpine regions, than to the tamer inequalities of less elevated countries. Huge massess of rock rise at once from the plains, and raise their peaked summits to an immense height in the air, while projecting crags spring from their rugged flanks and threatening the valleys below, seem to bid defiance to the laws of gravitation. Around the base of these frightful eminences are strewed numerous loose and unconnected fragments, which time seems to have detached from their parent mass; and when we examine the rents and ravines which accompany the over-hanging cliffs, we expect every moment that they are to be torn from their base, and that the process of destructive separation which we had only contemplated in its effects, is about to be exhibited before us in tremendous reality. The strata of lunar mountains called the Appennines, which traverse a portion of her disc from north-east to south-west, rise with a precipitous and craggy front from the level of the Mare Imbrium. În some places their perpendicular elevation is above four miles and though they often descend to a much lower level, they present an inaccessible barrier to the north-east, while on the south-west, they sink in gentle declivity to the plains.

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'The analogy between the surface of the Earth and Moon fails in a still more remarkable degree, when we examine the circular cavities which appear in every part of her disc. Some of these immense caverns are nearly four miles deep and forty miles in diameter. A high annular ridge, marked with lofty peaks and little cavities, generally encircles them; an insulated mountain frequently rises in their centre, and sometimes they contain smaller cavities of the same nature with themselves. These hollows are most numerous in the south-west part of the Moon; and it is from this cause that that portion of this luminary is more brilliant than any other part of her disc. The mountainous ridges, which encircle the cavities, reflect the greatest quantity of light; and from their lying in every possible direction, they appear near the time of full Moon like a number of brilliant radiations, issuing from the large spot, called Tycho.

'It is difficult to explain, with any degree of probability, the formation of these immense cavities; but we cannot help thinking,

that our Earth would assume the same figure, if all the seas and lakes were removed; and it is therefore probable, that the lunar cavities are either intended for the reception of water, or that they are the beds of lakes and seas which have formerly existed in that luminary. The circumstance of there being no water in the Moon is a strong confirmation of this theory.'

Dr. Brewster closes his supplement with a table, containing the elements of the orbits of the planets and several other particulars. In this, we are surprised to find, that he has not availed himself of the later corrections and improvements.We have, for instance, the longitude of the nodes for the year 1750, the inclination of the orbits, without the variation, for 1780, and the place of the aphelia for 1801, printed 1800; whereas the practice has been for some time to refer all these to the beginning of the present century, and to give the place of the perihelia instead of that of the aphelia for the sake of preserving a uniformity in this respect between the planets and comets. The secular variations of the nodes and aphelia are given not according to the latest corrections, and the reader is left to find out as he can when they are additive, and when subtractive, and whether they are absolute, or whether they are to be referred to the equinox. The eccentricities are in parts of the earth's mean distance considered as 100000, instead of being expressed in parts of the semi-major axes respectively. There are morever some important mistakes, besides such as are evidently typographical. The Moon's mass is stated to be 0.025, instead 0·0146, and that of Mars at 0·0875 instead of 0.1294, the earth's being considered as 1. On the whole, this table, which is a sort of an abtract of the author's view of the subject, when compared with similar ones given by Laplace, Biot, Delambre, or by Mr. Woodhouse, will be found to be more or less incorrect in a greater part of the articles contained in it.

We have adverted to what we conceive the most exceptionable parts of the editor's labours. In others, he has given abundant proof of learning and extensive research; and the matter, which he has collected, appears to us, for the most, to be well arranged. His style is perspicuous, and animated, and more highly wrought than we generally meet in productions of this nature. He is sometimes, however, a little too lofty, and too ambitious of rhetorical ornament.

We have confined ourselves principally in the remarks we have offered, to the faults and defects of this work, in the hope that some exertions may be made towards procuring one more respectable, and more worthy of the nature and present state of the science. Were we already supplied with such a treatise, adapted to the higher class of readers, we should not regret the republication of this, as it may be useful in academies and schools, and to a large description of persons whose education and pursuits do not lead them to inquiries of a more refined and difficult character,

ART. VIII. Inaugural Address, delivered in the Chapel of the University at Cambridge, November 5, 1817. By Levi Frisbie, A. M. Alford Professor of Natural Religion, Moral Philosophy, and Civil Polity in Harvard University. University Press, Hilliard & Metcalf, 1817.

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WE in this country have great reason to congratulate ourselves upon the rapid improvement, which has taken place. within a few years in the state of our literature. Without doubt, there is not in any nation, so large a proportion of readers of some degree of cultivation and refinement. One of the most striking evidences of our literary improvement is to be found in the character of many of our popular addresses, which indicate at once the talents of the speaker, and the estimate which he has formed of the information, good taste, and good sense of those whom he is addressing. Of these it would be impossible to select a more favourable specimen, than the discourse now under review, which, though pronounced before the University in Cambridge, upon the occasion of the author's inauguration as Professor,* may yet be regarded as a popular address, when we consider the numerous audience which attends upon such occasions. It is partly as affording evidence of the good state of our literature, that we are desirous of directing the publick attention to it; but principally on account of its intrinsick value. We are persuaded that so far as we are able to make it more known, we are doing service to the cause of letters, and of morals.

* See our last number, p. 146.

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