NICHOL'S PHCE110MENA OF THE SOLAR SYSTEM.

ALTHOUGH appearing second in point of time, this volume, which treats of our own planetary system, is in reality a precursor of the Architecture of the Heavens, that, travelling far beyond our sun and his attendant worlds, laid open the stupendous won- ders of space, so far as human faculties can traverse it. Hence there is necessarily less both of grandeur and of novelty in the second work than the first. Thousands of " firmaments," each containing countless suns and their attendant planets—the forma- tion of new " milky ways,' going on under the very eye of the astronomic observer—was a subject more overwhelming to the mind by its novelty and vastness, than an exposition of our plane- tary system, with which we have a sort of school or " popular ency- clopaedia" acquaintance. Dr. l■Ticytot, may perhaps have felt this inevitable deficiency of subject, and aimed at removing it by spurring Pegasus, and urging his native poetical temperament till it runs into rhapsody. At all events, there is in this volume an occasional appearance of art striving to become effective, and of enthusiasm swelling itself into turgidness,—a natural fault. we suspect, of Dr. Nicuois genius, over which he will do well to keep watch.

Having thus freely stated the drawbacks of the volume, we turn to the pleasanter task of noting its excellences, which are of the highest kind. The charm of novelty is often imparted to a worn subject, and the most seemingly abstruse points are made perfectly clear to an attentive examination. By throwing the exposition of the solar system into the form of a history of astronomical discovery, Dr. NICHOL not only introduces the truths of astronomy in the way in which the human mind first received them, but he gives an interesting coup doeil of the his- tory of the science, as well as a curious chapter of the human mind. By this mode, too, he is enabled to intermingle with an exposition and history of astronomy, characteristic biographical notices of those men whose labours advanced the science. Dr. NICHOL has also animated his knowledge by a composition lucidly eloquent ; which, though sometimes, as we have said, forced and overdone, always attracts and sustains attention.

The volume commences with a picture of the heavenly bodies as they appear to uninstructed observers; and then proceeds to sketch the astronomical theories of the ancients, as perfected by PTOLEMY, and afterwards overlaid and disfigured by the logical fancies of the middle ages. Almost as soon as this system appeared dm!), established by the work of PURBACH, the "unknown Polish ecclesiastic" COPERNICUS arose, to destroy for ever the Ptolemaic theory ; to maintain that the earth was not fixed, but moved round the sun ; and to degrade this globe from its fancied preeminence as the centre of the heavenly host, to the state of an inferior planet. Having sketched the life and discoveries of this founder of true astronomy, Dr. NICHOL proceeds to the man whose invention and use of the telescope enabled some of the doubts and difficulties attendant upon the views of COPERNICUS to be cleared up and the objections answered. " The starry GALILEO and his woes," is followed in the field of discovery by the laborious, observing, and noble Dane, TYCHO BRAHE; of whose singular castle at Uraniburg, (a little islet in the Baltic,) of whose singular study, of whose singular globe, and of whose singular effigy, we have characteristic descriptions and engravings, from Tvetto's own book. Banished by his Sovereign for the offence given to courtiers by his rough and plain-speaking ways, TYCHO luckily became associated with a genius capable of using the immense mass of minute astronomical facts which he had collected. This individual was JOHN KEPLER; who, availing himself of TYCHO'S observations, corrected the system of COPERNICUS, by proving the true form of the orbit in which the planets revolve; established the system, by demonstrating that the apparent irregularity of the planetary motions was really regular ; and extended it, by showing that the solar system was knit together, forming one con- nected whole instead of a series of independent members. Much as the human intellect had accomplished in tracing the courses, watching the motions, and detecting the relations of the sun and its attendant worlds, still it was of a formal and outward kind ; the living principle—the law which compressed the matter of each planet, which caused it to describe the peculiar elliptical orbit it travels, and which holds together the whole system in such won- drous harmony, was a mystery, till NEWTON discovered the law of gravitation. Other astronomers, following the path he opened, bare made considerable additions to science since his day ; but the principal ones to be noticed in this cursory description,---..are tho discovery by WILSON and HERSCHEL of the true nature of the in the sun, with the singular deductions as to his atm: spheres which it led to, and the map of the moon by B,„a IM MADLER, a reduced copy of which illustrates the volume. However clearly the more teaching parts of the book may be expounded,—and we suspect its very clearness will induce some loose-judging persons to deem it superficial,—yet, resting upon mathematical demonstration, they require diagrams. We Rust therefore confine our extracts to the speculations suggested by astronomy, or to some anecdotes of astronomers. After having borrowed HERSCHEL'S illustration, to show the impossibility of presenting to the eye the respective distances of the planets from the Sun, Dr. IslicHot indulges in some

SPECULATIONS ON THE PLANETS.

I. Of the Sun's train of eleven planets, all regularly revolve around bias and so far as ascertained, also rotate on their own axes; the former motion eon: stituting the year of each orb, and the latter its succession of day and nigh:, But how various are the absolute durations of these important periods in the different bodies ! The following table compares them with those of the Emil, moats. 11‘ Hod of Rotation, or nearly thePeriod of liciolinion in L'XI:f. a Dgnai6ride :.1 igh • _e n.Lengtho,4,1;.eara. Mercury 24° 1 aO 31 "12 tt.

Venus Earth 1 10 21

27

in judging of the probable effect of this signal variety upon the internal etc. portly of the several planets, we must either abandon speculation as vain and

impossible, or be conteut with a few guesses drawn from a supposed anale,f with the Earth. The latter course, indeed, is almost equivalent to the farmer; kr it conducts us among circumstances where we are only bewildered, seeing that

imagination fails in the effort to combine and embody them. How, for instance, can that contrast be pictured, which subsists between the two extreme babe; of our system—Uranus and Mercury ; the one hurrying through its rettle4 cycle of seasons in three months, and the other spending on the same relative

change eighty-four terrestrial years? A tree in 51ercury—if such there is-. WORM gather around its pith or axis three hundred and thirty.six of those well.

known circular layers, in a time during which the sluggish vegetation of Uranus

would only have deposited one : and a full and burning lifetime, made up of rapid sparkling joys and acute sorrows, would, in so chaos neighbourhood of tie Sun, be compressed within a space hardly adequate on Earth to lead youth to its meridian ; while at that outer confine a slow pulse and drowsy blood might sustain for centuries a slumbering and emotionless existence! The yes. lion is further complicated, if we refer to the rapid succession of day and night in the remote planets ; perhaps modifying, by the activity it excites, thecompa• rative torpidity due to the length of the year. We can form no notion of the physiological consequences due to a recurrence of day and night within the brief period of nine or ten hours. II. The very different distances of the planets from the Sun is a second ob- vious source of remarkable contrast. Those proportionate distsuces may be guessed from the illustration at the commencement of this chapter ; but Figure 2, Plate Xi., will further aid the imagination. It shows the comparative cite of the Sun when seen from the different bodies in our system ; dwindling gm dually from the mighty globe visible at Mercury, to that comparatively small orb which enlightens the landscapes of Uranus. It is computed that at Ma- cury the Sun shines with seven times the intensity experienced on Earth, ail that at Uranus his radiation is at least 330 times weaker than with us. Between Mercury and Uranus, therefore, besides the difference occasioned by the rapid and slow alternation of seasons, there is an actual disproportion in the quintityof solar light shed upon them of upwards of 2,000 to 1. And yet Uranus is Dot obscure, nor its plains benighted. The light of our full moon has been computed as about 300,000 times weaker than that of the meridian sun ; so that the light• giver can bestow, even on his remotest attendant, as much light at noonday as if nearly 1,000 of our moons were shining in its sky. In these remoteregion we likewise find, as if in some compensation, a singular extension of that pro. vision which so muds adorns our Earth—the provision for throwing part of the solar light on the dark hemisphere of the planet, by reflection from moans. la Mercury, Venus, and Mars, the midnight vault is bespangled only with star; but Jupiter has four moons, each larger than ours, constantly circling around him, varying his skies by their beautiful and ever-changing phases; Saturable seven ; and, according to Sir William Herschel, Uranus has six. The subject is further continued with reference to the respective densities of the planets, and the character of the bodies which con- sequently can exist on them— If the varying periods of the revolutions of the planets and their varying distances from the Sun, intimate a necessarily diverse external aspect, the right interpretation of the previous table will emphatically show that the internal varieties cannot be less striking, and that only a fragment or stray leaf of era. istence is found within those four cardinal points which are the cameo of our world. For observe the necessary and essential difference of such stolid in material composition. The matter of which Mercury is made up is nearly four times heavier than that which composes our world ; while Saturn ists light as cork. What can be the surface of Mercury? where the locality of water in Saturn ? And again, howgreat the influence of such varieties upon the forms of organization ! Upon the weight or mass of each planet depends in chief part the weight of a body at its surface. Now the size attained by organized families must be regulated ultimately by the power of the materials of which they are composed, to resist the depressing force of their own weight. lf, for instance, the enormous Bro. bab—that grandest proof of the strength of the vegetable fabric—were sod. denly to become twenty times heavier than it is, or it a North American pm received an equal addition of weight, the fibres which sustain them would be bruised, and they would fall crashing to the ground. So, in the animal world, the elephant or the old magatherium are, perhaps, the mightiest fabrics which can be sustained by the utmost strength of bone ; whence it may be, among other causes, that the drying up of interior lakes (on the waters of which they often reposed their enormous weights) has caused the disappearance from our world of the gigantic dinotheria. Now, give a man twenty-seven times his present weight, i. e. transport him to the surface of the Sun, and every boot which supports him would crumble in one instant into powder. But if, 00 visiting the Sun, we must consent, for security, to be transformed into scar beetle or caterpillar, a visit to Vesta would soothe the vainest ; for there-000 • For the sake of simplicity, the year is here accauaIo exactly 365 clays,10163 month 30 days.

Mars

Vesta,

23

21

23 56 24 39

...... .. 0 7 5 1* 0 t

3

Juno unknownCeres

Pallas Jupiter 9 56

Snturn 10 29

Uranus unknown ell 4 4 13 4 11

11 10 17 17

29 5 24 84 planet whose whole surface is not greater than the kingdom of France- gc dimensions are possible with our present structure, and vertical leaps of some sixtyfeet would assuredly gladden the heart of the most ambitious athlete. It were the easist undertaking to push these conjectures further ; per-

haps they already verge on the ludicrous. It is one great use and function of all such speculations to arouse due conceptions of the variety of the universe, a variety coextensive with its vastness, but through which law unquestionably prevails and rules and orders all.

The following speculation, on the possible extinction of the Sun, follows a description of the discoveries of WILSON and HERSCHEL, already alluded to. The question cannot fail to suggest itself here—whether this light-producing power may depend, in degree, on the probably ever•changing electric elate of a growing globe—whether the Sun is now as he was and will ever be, or only in one state or epoch of his efficacy as the radiant source of light and heat ? It seems to me most worthy of consideration, whether those puzzling phenomena, indicative of an altered heat in our Earth, may not pertain in part to this source —to the onward progress of our heat-giver through the destiny to which law foreordained him ? The changes referred to stretched over epochs in which man was not present, and when, of course, their progress could not be marked ; but even now, due attention is not paid to the momentous subject ; for the delicate acianetnent of the Sun's direct strength is of greatly- more consequence than that temperature which arises for the most part from a mere terrestrial meteorology. The further heavens, however, come here in aid. atd supply this gap in our knowledge; appearing to substantiate the possibility, if not the reality, of such changes. The new star in Cassiopeia, seen by Tycho, for in- stant*, indicated some great change in the light and heat of an orb, far more probably than a mere orbitual motion. That star never mnred from its place ; and, during its course from extreme brilliancy to apparent extinction, the colour of its light altered—passing through the hues of a dying conflagra- tion. Can aught of this be seen iu the Southern star, one of Sir John Herschel's 'pails, which is gradually clothing itself with an extreme brilliancy ? Many other stars have altered slowly in magnitude, also preserving rigorous invariability of place; and some, as Sirius, have changed colour ; this star having turned from the fiery dog•star of old time9, led and fiery as .Mars, into the brilliantly white orb now adol sing our skies. Is it not likely, then, that the intrinsic energies to whose development these phenomena moist be Ming, act also in our Suu that, in short, he also may pass through phases, filling up inyt lads of centuries • once, it may be, shining on Uranus with a lustre as burning us that which now dazzles Mercury ? How vast are the effects involved in such a change ! The rays of the Sun are nut luereis light-giving ; for, combined with these, in the same beam or pencil, there ate rays whose functionis heat-giving, and others equally distinct, which are product ice of chemical influence. Nose, in the pro- bable march of our linnimay, how great a variety in the relations of these three systems of rays may be involved, and, of course, what diversities in his action on his dependents! Imagination, clinging to such conjectures, passes to the august conception of this muster of surrounding worlds, this majestic globe, himself organized, progressing slowly chi ought has destiny, ever acting, as he moves °matt!, on the inner and proper principle of each planet ; drawing from it (which also may itself vary, according to some intrinsic energy or law) every form and manifestation of which it is capable, and conducting them all through a long and wondrous history. How emphatically dues even this guess inform us that we see only sIetchea of the history of things—that a leaf or two of the mystic volume is all that ever will be read by man !

THE END OF TYCIIO BEARE.

Tycho removed to Germany, where lie obtained a friend in the Emperor Rodolphus, and an asylum at Piague. Suite would have been happy in that new retreat, and have forgotten Denmark. Not so Tycho. His spirit was broken, and lie drooped. Rugged though lie was, lie could not forget [-rani- burg; and he always spoke with a doting longing of the scenes and friends of his youth, the country which had exiled him, and of Hues, his little island, the theatre of the play of his dearest affections, the spot with which he associated his labours and glory. Notwithstanding the kindness of Rodolphus and the companionship of Kepler, he felt as in a strange land; and disease from an accidental cause carried him off at the age of fifty-five. Sad and too early termi- nation of so glorious a career ! many even then were the hearts which, when the tidings reached them, felt blank, fur they knew that a great man was gone. During the last night of his life,, he was afflicted by delirium, interrupted by a few intervals, in which he seems to have been employed in reflecting on his career, and surveying his labours ; for he repeatedly exclaimed, "1 have Out lived in vain." Most true! of all the observers of the ancient world, lie alone is worthy to stand beside Ilipparchus ; they are twin names, which should never be dissociated. In awarding hint the merit which is his due, let us forget his deficiencies: his failings belong to the humanity of every age—his greatness WAS original, and his own !

Here is an account of the full discovery of gravitation. The calculation was not to show that it influenced the courses of the planets, (which NEWTON had already proved,) but to demonstrate that it was the pervading principle of material nature, operating equally upon a falling stone, upon the flowing tides, upon the revolution of the moon, and the orbits of the planets. The attrac- tion of the earth over the moon, it may be gathered, was the problem to be resolved.

The accurate resolution of the problem, it will be seen, depends on the accu- racy of the data, on the known diameter or size of the earth, and of the dis- tance of the moon. When Newton first undertook it, his data were not accu- rate. The result, of course, was incongruous with his conjecture ; and with the honour of a man who loves truth, he threw his theory aside. Three years after, truer measures of the required quantities were obtained, and he revised

his old calculations. It is recorded, that towards the close of his work—when itseemed that the results were coming in accordance with his surmise—when he felt on the verge of obtaining one of the most important laws ever revealed to man—when, in short, he was recognizing that which for evermore would bind the heavens to the earth, and constitute himself the first of philosophers—the nerves of the great man quivered, and he could not finish his task. He called in the aid of a friend, pacing his room in tumultuous agitation, while the few last arithmetical operations were being concluded, and perhaps as fearful at the moment lest his conjecture might be true as that it should prove fallacious. It is difficult now to conceive the intensity of Newton's feelings when the re- sult was finally announced to him. 13v effect of familiarity it has become com- mon; hat revert back to the revolution it made in man's knowledge of the universe. No order or connexion among events had then been discovered save what lay in Kepler's laws ; which, limited as they are, it bad required the in • tellect of the previous world to elaborate t but here was a tevelatiun, not merely tracing some further small analogy, not binding together more closely the cha- racter of the planetary orbits, but uniting them in all their majesty with the simplest of terrestrial phenomena, and demonstrating, that over a drop of spray, tossed in an apparently random course through the gulf of a cataract or across the rocky barriers of a raging ocean, is dominant the same regulating power which retains the great planets with their moons in their sweep around the sun. Knowing how trifling a novelty may agitate the firmest minds, no wonder that Newton was affected by an uncontrollable tremor. Aod it may be that, at that moment, he perceived not only the extent of those great tidings of which he had become the herald, but also that an entire clamp had passed over himself—that, instead of the persevering and successful pnsate student, he bad become a name which would never die from the minds of men.