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planets may have in this respect, it is impossible to know, but it is probable ihat the moon has become highly magnetic, in consequence of her proximity to the earth, and because her greatest diameter always points towards it.'-pp. lix, Ix.
After explaining the nature and the end of astronomical knowledge, Mrs. Somerville proceeds to trace the history of the progress of its improvement, from the discovery of its first rudiments, to the date of what may be called its comparative perfection. The law of gravitation, found out by Newton, forms the great foundation of our acquaintance with the heavens. Simple, however, and universally applicable as this law is, yet, as applied to the motions of the planets, it presents problems extremely difficult of solution. It is the principal object of Mrs. Somerville's work to facilitate the explanation of these difficulties, and for that purpose, she chiefly relies on the immortal work of La Place. In the first book are explained the laws by which force acts upon matter. This explanation is altogether derived from the Mecanique Celeste, and in general, Mrs. Somerville, instead of tamely translating the language of La Place, more properly chooses to explain the methods by which that distinguished man arrived at the results of his glorious labours. In the second book, the author compares the laws of the action of force upon matter, with the actual motions of the heavenly bodies; and to each of the planets she devotes a chapter, in which the phenomena that they present are described with equal felicity and accuracy. The number of diagrams employed by Mrs. Somerville to assist the elucidation of her meaning, and the purely algebraical character of most of her explanations, place it altogether out of our power to pursue the course of reasoning or description which she has adopted. There are, however, at intervals, curious observations, and not infrequently some important facts, to be met with in her pages, which cannot fail to excite the attention of general readers. Of the existence of an atmosphere about each of the planets, no doubt can be now entertained. The author observes, that the presence of this atmosphere is proved by the spots and belts which are observed on the discs of the planets.
* These spots,' observes Mrs. Somerville, 'appear like clouds driven by the winds, especially in Jupiter. The existence of an atmosphere round Venus is indicated by the progressive diffusion of the sun's rays over her disc. Schroëter measured the extension of light beyond the semicircle when she appeared like a thin crescent, and found the zone that was illuminated by twilight to be at least four degrees iv breadth, whence he inferred that her atmosphere must be much more dense than that of the earth. A small star hid by Mars was observed to become fainter before its appulse to the body of the planet, which must have been occasioned by his atmosphere. Saturn and his rings are surrounded by a dense atmosphere, the refraction of which may account for the irregularity apparent in bis form : his seventh satellite has been observed to hang on his disc more than 20' before its occultation, giving by computation a refraction of two seconds, a result confirmed by observation of the other satellites. An atmosphere so dense must have the effect of preventing the radiation of the heat from the surface of the planet, and consequently of mitigating the intensity of cold that would otherwise prevail, owing to his vast distance from the sun. Schroëter observed a small twilight in the moon, such as would be occasioned by an atmosphere capable of reflecting the sun's rays at the height of about a mile. Had a dense atmosphere surrounded that satellite, it would have been discovered by the duration of the occultations of the fixed stars being less than it ought to be, because its refraction would have rendered the stars visible for a short time after they were actually behind the moon, in the same manner as the refraction of the earth's atmosphere enables us to see celestial objects for some minutes after they have sunk below our horizon, and after they have risen above it, or distant objects are hid by the curvature of the earth. A friend of the author's was astonished one day on the plain of Hindostan, to behold the chain of the Himala mountains suddenly start into view, after a heavy shower of rain in hot weather.
• The Bishop of Cloyne says, that the duration of the occultations of stars by the moon is never lessened by 8" of time, so that the horizontal refraction at the moon must be less than 2": if therefore a lunar atmosphere exists, it must be 1000 times rarer than the atmosphere at the surface of the earth, where the horizontal refraction is nearly 2000". Possibly the moon's ato:osphere may have been withdrawn from it by the attraction of the earth. The radiation of the heat occasioned by the sun's rays must be rapid and constant, and must cause intense cold and sterility in that cheerless satellite'—p. 400.
The peculiarities of each of the planets are well described by Mrs. Somerville. Mercury's motions, it appears, are less disturbed than those of any other body. He sometimes is seen as a morning and sometimes as an evening star. Occasionally he passes over the sun's disc, like a black spot, and the partial eclipse of the sun's light, which is produced by the transit of Mercury, proves that it is an opaque body, which shines by reflected light alone. Venus is distinguished as the only planet mentioned in the Sacred Writings. It has also been celebrated in the poet's song from the era of Hesiod, to that of our own Milton. She is the most brilliant of all the planets—but, like all beauties, her splendour is very variable. Though her disc increases with her distance from the earth, yet her lustre decreases according to that distance. It is only in a mean position that Venus assumes all her natural brilliancy, and the periods at which she returns to this position are separated by intervals of about eight years. On such occasions this planet is visible to the naked eye during the day, but at all other times she may also be seen, but not so distinctly, during the day, every eighteen months. One of the principal apparent peculiarities of Mars is, that bis disc is occasionally gibbous—and that there are spots near his poles, which augment or diminish according to the degree of exposure to the sun, and which give to the spectator the notion of great masses of ice. The newly discovered planets, Vesta, Juno, Ceres, and
Pallas, whose orbits are situated between those of Mars and Jupiter, are all nearly equidistant from the sun. They are altogether invisible to the naked eye—their apparent diameters, with the exception of Juno, scarcely amounting to the fourth of a second, or sixty-five miles. Juno, however, is supposed to have a real diameter of two hundred miles. We pass over the remarks of the author on the remaining planets, in order that we may be enabled to insert the account which Mrs. Somerville gives of the present state of our knowledge of the sun.
· The sun viewed with a telescope, presents the appearance of an enormous globe of fire, frequently in a state of violent agitation or ebullition; black spois of irregular form rarely visible to the naked eye sometimes pass over his disc, moving from east to west, in the space of nearly fourteen days: one was measured by Sir W. Herschel in the year 1779, of the breadth of 30,000 miles. A spot is surrounded by a penumbra, and that by a margin of light, more brilliant than that of the sun. A spot when first seen on the eastern edge, appears like a line, progressively extending in breadth till it reaches the middle, when it begins to contract, and ultimately disappears at the western edge: in some rare instances, spois re-appear on the east side; and are even permanent for two or three revolutions, but they generally change their aspect in a few days, and disappear: sometimes several small spots unite into a large one, as a large one separates into smaller ones which soon vanish.
• The paths of the spots are observed to be rectilinear in the beginning of June and December, and to cut the ecliptic at an angle of 7° 20'. Between the first and second of these periods, the lines described by the spots are convex towards the north, and acquire their maximum curvature about the middle of that tiine. In the other half year the paths of the spots are convex towards the south, and go through the same changes. From these appearances it has been concluded, that the spots are opaque bodies attached to the surface of the sun, and that the sun rotates about an axis, inclined at an angle of 7° 20' to the axis of the ecliptic.
The apparent revolution of a spot is accomplished in twenty-seven days; but during that time, the spot has done more, having gone through a revolution, together with an arc equal to that described by the sun in his orbit in the same time, which reduces the time of the sun's rotation to 25° 9' 36".
* These phenomena induced Sir W. Herschel to suppose the sun to be a solid dark nucleus, surrounded by a vast atmosphere, almost always filled with luminous clouds, occasionally opening and discovering the dark mass within. The speculations of La Place were different: he imagined the solar orb to be a mass of fire, and that the violent effervescences and explosions seen on its surface are occasioned by the eruption of elastic Auids formed in its interior, and that the spots are enormous caverns, like the craters of our volcanoes.
• Light is more intense in the centre of the sun's disc than at the edges, although, from bis spheroidal form, the edges exhibit a greater surface under the same angle than the centre does, and therefore might be expected to be more luminous. The fact may be accounted for, by supposing the existence of a dense atmosphere absorbing the rays which have to penetrate a greater extent of it at the edges than at the centre; and accordingly, it appears by Bouguer's observations on the moon, which has litle or no atniosphere, that it is more brilliant at the edges than in the centre,
A phenomenon denominated the zodiacal light, from its being seen only in that zone, is somehow connected with the rotation of the sun. It is observed before sunrise and after sunset, and is a luminous appearance, in some degree similar to the milky way, though not so bright, in the form of an inverted cone with the base towards the sun, its axis inclined to the horizon, and only inclined to the plane of the ecliptic at an angle of 7°; so that it is perpendicular to the axis of the sun's rotation. Its length from the sun to its vertex varies from 45° to 120°. It is seen under the most favourable circumstances after sunset in the beginning of March : its apex exterds towards Aldebaran, making an angle of 64° with the horizon. The zodiacal light varies in brilliancy in different years.
• It was discovered by Cassini in 1682, but had probably been seen before that time. It was observed in great splendour at Paris on the 16th of February, 1769.
• The elliptical motion of the planets is occasioned by the action of the sun ; but by the law of reaction, the planets must disturb the sun, for the invariable point to which they gravitate is not the centre of the sun, but the centre of gravity of the system; the quantity of motion in the sun in one direction must therefore be equal to that of all the planets in a contrary direction. The sun thus describes an orbit about the centre of gravity of the system, which is a very complicated curve, because it results from the action of a system of bodies, perpetually changing their relative positions; it is such however as to furnish a centrifugal force with regard to each planet, sufficient to counteract the gravitation towards it.
· Newton has shown that the diameter of the sun is nearly equal to 0.009 of the radius of the earth's orbit. Jf all the great planets of the system were in a straight line with the sun, and on the same side of him, the centre of the sun would be nearly the farthest possible from the common centre of gravity of the whole; yet it is found by computation, that the distance is not more than 0.0085 of the radius vector of the earth ; so that the centre of the sun is never distant from the centre of gravity of the system by as much as his own diameter.'—pp. 401–403.
Unfortunately, the strictly scientific nature of this work, and the numerous subdivisions in which the subject is necessarily considered, prevent us from giving to the reader that complete description of its contents, which would enable him to form a true judgment of its various merits. Taken altogether, the production does honour to the age in which we live—but as the exclusive performance of a female, it must be regarded as a prodigy of intelligence and mental industry. It is a subject worthy of national congratulation, that a lady of extraordinary talents, and of sufficient ambition to trespass beyond the restraints imposed upon her sex, should enlist in the ranks of the missionaries of " useful knowledge.” The cooperation of such auxiliaries in any enterprize of moral, or even physical amelioration, must always be a desirable object, since it is a part of their nature to invest with a charm of almost invincible attraction, every project or design which may be placed under their
management. Happy is it then, that under a sanction so influential, and under auspices so fortunate, the study of the works of the creation are strongly recommended. The contemplation of the heavens, which, from the erect posture given to him, exclusively of all animated beings, would appear to be one of the primary duties imposed on man, is yet one of the inost powerful means of elevating and dignifying his nature. It teaches him to look beyond
ignorant present," to raise his wishes, his hopes, his desires, far beyond any objects of gratification which are to be found in this perishable sphere; it imparts to his soul some knowledge of that all-wise and all-provident First Cause, which, assuredly, would never have implanted in his soul a thirst of immortality, without intending to gratify the appetite.
NOTICES. Art. XII.— The Ladies Cabinet of a highly diversified and entertaining
Fashion, Music, and Romance. miscellany, ull for the price of sirNo. I. 18mo. London: G. Hen pence! We should hardly have bederson. 1832.
lieved the fact, if the book were not
before us with the price marked The first number of this new jour- upon it. The steel engraving dal now lies before us, and we alone would, in our opinion, be must say that it appears to us to worth five or six times that suin. be, as the prospectus states, really, But we presume the publisher must “ one of the miracles of the age." sell some thousands of his journal, It contains three or four plates of in order to afford him a fair comfashions, well coloured, and afford pensation for his outlay. Among ing the ladies a correct idea of the the articles, besides the tale of changes which have taken place in Eugene Walmer," there are two the style of costume during the last others, “ The Haunted Casket”. month. In addition to these, it and “The Deserted Mother,” wbich gives a steel engraving, exceedingly cannot fail to excite the attention well executed, representing a “de of the reader. There is a ballad serted mother" with two children on the “ Italian Boy,” a conver in her arms, in the back ground a sational glance at passing topics, field with reapers at work; and under the head of “ At Home,” a prefixed to the first article, the tale review of Sir Walter Scott's last of “Eugene Walmer," is a very neat work, an essay on
Female Eduwoodcut of a scene connected with cation,” and on the “ Plurality of the story. There is next a song, Worlds.” To these are added a called “ The Wedding Bells," set variety of miscellaneous topics, to music in a large sheet, which connected with literature, with folds into the journal, the words passing events, and the drama, and the music being both original ; - making on the whole, we and as if these were not enough for suppose, incomparably the cheapthe money, we have sixty pages
book that ever was pubof letter press, forming for the most lished in any country. We subjoin, part an original, and in the whole as a specimen of the poetry, the