DR. NICHOL ON THE SYSTEM OF THE WORLD.

Tans volume is a sort of sequel, or in the language of the author of the Vestiges of Creation an "explanation," of Dr. Nichol's former work on the Architecture of the Heavens. In the opinion of Dr. Nichol, the power

of Lord Rosse's great telescope, by resolving the supposed nebulous fluid into stars, has overthrown the nebular hypothesis of the elder Herschel.

As an important section of the Professor's first book was devoted to the exposition of this theory, he wishes to correct an erroneous view, which he was a means of widely disseminating ; and to rescue the memory of Herschel from any suspicion of rashness in forming his speculation, which was a natural and legitimate deduction from the data within his reach. To make these positions clear, of necessity carries Dr. Nichol over the field of his former work ; and the earlier part of Thoughts on some Important Points relating to the System of the World is a cor- rection by later discoveries of several views, or rather speculations, before advanced. To this is added a further review of La Place's theory of the formation of our solar system; the mathematical and chemical arguments in favour of which are not overthrown by the alleged dissolution of the nebular hypothesis, though La Place is deprived of an important piece of evidence. A very singular speculation or conjecture follows, touching the movement going on throughout the universe; late discoveries show- ing a high probability that not only our own solar but other systems have an onward motion through space, over and above their own re- volving and orbital motions—that these systems seem slowly though surely drawing near each other ; and there is a possible inference that the greater will attract the lesser, the existing state of creation be broken up, and a new and more advanced condition arise, in obedience to that law which is seen to operate wherever we can collect data to trace its operations, the law of progress.

Having traversed the sidereal universe so far as the assisted eye of the astronomer can penetrate, Dr. Nichol turns to our own Earth, and the neighbouring planets as far as they can be used to throw any light upon its history. Geology is here the leading subject; but the object is pretty much the same as in the former part. The enormous duration of the system, measured by our notions of time—the state of continual change which is everywhere traceable—and the evident progress of such part of creation as we can submit to any test—are the main topics. In the course of their discussion, Dr. Nichol brings together some of the More striking facts both of astronomy and geology, making them his own by applying them to his exposition of the Earth's cosmogony: but in looking at the vastness and duration of the material world, he does not forget the dignity of the moral. According to the individual temperament, there are passages where the reader will almost be driven to "weep or smile" at his own insignificance, and the utter littleness of all we consider great ; till Dr. Nichol calls attention to the dignity of mind and all that is connected with its laws ; and finally, rising still higher, he points out the possible advance of man in the knowledge of creation and of the Crea- tor's laws, and enforces the same submissive reliance on "one disposing power" as was inculcated by the great moral poet in his "Essay on Man."

Many of the topics handled in this volume, and perhaps the very basis of the whole, partake of that daring character from which very excellent though narrow-inhaled persons shrink as impious, while men of a more prac- tical cast may look with some distrust upon the utility of the inquiries. It may therefore be proper to say, that a profound spirit of natural piety animates the System of the World, and that Dr. Nichol passes no fair Opportunity of recording his opposition to such views as those promul- gated in the Vestiges of Creation. He as distinctly announces that he will be guided by "a cautious and reverential criticism" ; carefully separating the hypothetical, which is based upon an imperfect or even a conjectural knowledge of facts, from those deductions which, whether true or false, rest upon an examination of data, that, like the geological rocks, can be seen and touched. In a critical point of view, however, it must be acknowledged that the necessary unsubstantiality of the premises may in the remoter speculations give something of a similar cast to their ex- position. This necessary defect is probably less felt in Dr. Nichors hands than it would be in those of any other person, from the completeness of his knowledge, and his power of popular exposition, which enable him to present the hypothesis as clearly as its nature admits, as well as from the style of his eloquence, which varies and rises with his theme,—plain in ex- position, pellucid in argument, but with something of a poetical vein when he ventures "beyond the visible diurnal sphere." The main interest of the book, after all, is perhaps less in its entirety than its parts or sections. These are of various character, with various interest. One of the most speculative and remote, (for the system will last our age,) yet at the same time one of the grandest, is the onward movement of the Sun and his satellites, the Earth of course included.

"But if the San moves, how are we to descry his changes? Not by sensation, not by direct observation on himself; for we would necessarily pass along, without jerk or disturbance, on through the abysses. One mode of discovery alone is open— that, viz., through the apparent change of place of the external stars. If our luminary is indeed rolling onward in some great path, the external orbs can no more remain in the same apparent positions than terrestrial objects which, when travelling, we swiftly pass; and although, on account of the great remoteness of these bodies from our sphere, and, as is probable, the comparatively slow motion of the Sun, it may require the lapse of ages and the exercise of the finest instru- ments to determine their apparent changes, these changes must—if they originate as I am supposing—all tell one tale, and, when discerned even roughly, point, by their direction and general characteristics, to that grand motion which is their cause. It was the rude view only which induced Sir William Herschel to an- nounce his early conclusions on this subject; which subsequent more full and accurate inquiry has thoroughly confirmed, viz, that the Sun, with his planets, is rapidly darting towards a point in the direction of the constellation Hercules."

"In recent times, Argelander of Bonn has discussed the subject with an accu- racy that leaves nothing to be desired; and the truth is firmly established, that we must accept the motion of translation of our Sun. The speculative views of this astronomer, that our orb is rolling around some grand central body, as he thinks opaque, situated near the bright spot in Perseus, are certainly questionable; bat it is undoubted that its motion is in the plane of the Miav Way, where the pre- ponderating attractive or centralizing power of our galaxy is naturally located. AO only do the general apparent displacements of the stars uphold this concln- sion, but what is still residual with regard to these motions seems to bestow on them all grand orbits, reconcileable in so far with Argelander's general views; so that our bed of stars no longer shines before the apprehension as a fixed and corn- plated stratum, but rather as one mass of unresting activities, working out, as time rolls on, its stupendous destinies."

The Chronology of the World is another section on a startling and stu- pendous subject. It is not so well illustrated without the diagrams which accompany the exposition ; but the general survey of the rocks of the globe may be sufficiently understood from the text alone.

"De Beaumont's chart, appended to his celebrated letter to Humboldt, emphati- ally illustrates this great subject; the visible progressive deposition and successive upturning of the sedimentary strata being there represented and impressed with a distinctness much surpassing aught attainable by elaborate descriptions. Stand- ing on the peaks of the Andes, whose origin belongs to the modern or existing epoch, how extraordinary and imposing the perspective which greets the view Nearest in point of time' but scattered over the world's surface like stars of the first magnitude through the heavens, we discern the mighty Himalaya, the peaks of Caucasus, the leading Alpine chain., Atlas, and other cognates. Lying between these—equally dispersed, but with thew distinctness diminished by distance—Mont Blanc rears its pinnacles the Cordilleras of Brazil, the Scandinavian Alps, and many minor parallel chains that burst from the interior daring the same epoch of commotion. -Farther among the recesses of the past, Lebanon arose, and the

Ural, and Corsica and Sardinia; beyond which, separated by an interval like that which divides the orders of fixed stars, we recognize the Pyrenees, Apennines, and Alleghenies. Across these latter peaks Ben Nevis and Snowdon are descried,

venerable with age; and, finally, the eye, wearied with the immensity of its range, loses itself, not unwillingly, amid the mists that overhang the origin of the transition rocks. Stupendous elaboration of Nature T.—as a whole, indeed, incon- ceivable: let us reflect, therefore, for a moment on some of its minor stages. On examining System IL on the chart, it seems clear, that when those commotitn. shook our planet, which, by twisting and upheaving the transition rocks, prodtteed the hills of the Bocage, not a trace of the great coal formation could have been iv being; for as exhibited there, it is lying evenly on the upturned edges of the other. But its for, and upheaval by the next system proves that before the earth was again disturbed, that profusion of vegetable life of which it is the significant remains had obtained its full development; or that this solitary period of terres- trial history included the apparition and prolonged existence dispersed widely over the earth's surface of continents or mighty islands, teeming with a gorgeous vege- tation the accumulation of whose leaves and stems through ages that are surely countless, produced the substance of that consolidated rock on which, during sub-

sequent revolutions, so many other depositions have since been laid down by the

sea. Now, the history of this single sera, necessarily including vest and multi- plied though orderly changes—for it contains the development of vegetable life until it reached an extreme exuberance—might well be estimated, according to our usual modes of thought, as an adequate history even for a world; but en the map it occupies the shortest span!"

We will take leave of Dr. Nichol's book with a subjeet snore within the common apprehension—the aspect of the planet Mars and of the Moon.

"Wherever the gaze of the telescope has clearly pierced, the surface of the planets are discerned to be marked by singular inequalities of outline; depriving

them entirely, as well as the Earth, of those perfectly smooth and unbroken

spheroidal forms, with which, under the simple action of the power of gravity they must all have been rigorously endowed. It were not desirable, nor is this the place, to explain under what evidence or aspects a fact so replete with interest can, in our present knowledge' be predicated in each of these various bodies; but, for illustration's sake, I shall refer a moment to what has been learnt of two of

our companions. One face or hemisphere of Mars when somewhat gibbous is

approximately represented in plate X. Now, as the shades charactenzing that picture are altogether stationary, they can have no relation to mere atmospherical phenomena, like the varying spots which often obscure the brilliancy of Venus;

and, therefore, it seems conclusive that they betoken terrestrial peculiarities; or, what is the same thing, show that tho body of the planet is divided between sub- stances of very different efficiency in reflecting the incident light. But, as tooter

absorbs much light, while land, on the contrary, reflects a large portion of all that falls on it, the distant view of our own globe would precisely resemble this

aspect of Mars in its leading features; and the different reflective power of various soils would bestow on the brighter Parts a mottled appearance. This analogy may seem very faint; but it is much strengthened by another singular phsenome-

non around the poles of our neighbouring planet. These are surrounded by bril- liant spots, exactly resembling our Polar snows; and, jut as with ours, eschpot contracts itself during the summer of the hemisphere to which it belongs, ally again enlarging with the approach and increase of winter. Appearances so nearly identical, reaching us through so vast a distance, mast be received as emi- nently emphatic; and certainly they press towards but one conclusion viz, that this picture represents the land and sea of Mars; and, therefore that the tele- scope has here unfolded, as an attribute of this orb, that uneven 'and broken surs face—that division into high land and, valley—which characterizes the vertical profile of the surface of the Earth. But if further distinctness be still wanting, we find it most abundantly in the Moon. The disc of our satellite, in every phase, exhibits its structure with a clearness as great as the aeronaut could deaire, when looking from a considerable elevation and through a pure atmosphere down on our terrestrial ranges. The surface of our luminary is visibly separated into plain and high land—the latter portion of it actually bristling with mountains: in some places isolated peaks disturb its evenness; elsewhere, long and lofty ridges stretch onwards, encircling extensive flats; and over a large area, those remarkable craters or ring-shaped mountains are studded with extraordinary profusion."