MILNER'S GALLERY OF NATURE.
In former times, a compilation very often assumed the character of an -original work. The idea of the book, let alone its plan, was less obvious than such things are at present, and therefore argued in the writer a bent of mind—a vocation to that particular task : many of the works that had to be consulted were not so ready of access as volumes are now and what was more, the nature of their contents was not so easily known without examination. Hence more of learning was necessary to rea- lize sufficient matter to form the plan, a great deal more of labour and reading to execute it. Some of these books, as Calmet's illustrations of the Bible, Potter's Greece, and Adams's Rome, still continue standard works to which modern discoveries and improvements are added : bat time has superseded many mere collections of scattered knowledge. This result was sure to be the case in advancing sciences, unless some extraor- dinary charm or knack of treatment induced people to read the book for its style, or its mode of exposition. Even in fixed subjects, as Scriptural or Classical antiquity, new lights or new speculations are continually coming up, and the fashion of composition changes so that unless a man ex- hausted the main body of the subject, and skilfully presented his learn- ing, some one borrowed his plan and labours, and improved him into oblivion.
• Expositions of existing knowledge, where no claim is made to new discovery, or novel views are not deduced from the known facts, have become so numerous, from the sixpenny catechism up to elaborate treatises, that character in compilation seems only attainable by two modes —the writer must be fully versed in the science of which he un- dertakes to exhibit a portion, and the knowledge itself be not already descended to the public ; or the largeness of his plan, and consequently the completeness of his matter, may overtop the lesser compilations by mere magnitude. Amongst the first may be ranked Dr. Nichol's popular exhibitions of the solar and stellar systems with the discoveries of the elder Herschel ; amongst the second may be placed the volume before us.
The Reverend Mr. Miler's Gallery of Nature derives its character from the variety of its subjects, the extent at which they are handled,
and the consequent fuhiess of matter in the book. Astronomy, physical geography, and geology, with a history of astronomical discovery, are his four great divisions. In astronomy, the sun and its planets are treated at length ; and comets, aUrolitw, the stars, and the nebulae, are each ex- hibited, Mr. Milner not giving up the nebular hypothesis of Herschel. In geography, the reader has the most striking features of the " earth and animated nature " presented to him ; and in the course of his examina- tion he is carried over the world, but not in the regular and systematic form of an instruction in geography : highlands, vallies, caverns, rivers, &c., with the distribution of plants, animals, and the human race, are treated of—not particular regions, though these may be noticed incident- ally. Geology is presented more systematically : first the general sub- jects, then the "rocks" and "systems," with the diluvinm and alluvi- um—the drift and erratic blocks, and the recent formations.
In so large a field, the facts and phrenomena, as they almost offer themselves, fiirnish matter full of interest ; and Mr. Milner is not defi- cient in the skill and cleverness of a litterateur. In running over his materials he selects the salient points of subjects, and varies his matter by anecdotes of men distinguished in science. But there seems to us some deficiency of wholeness, and of consequent continuity and homo- geneity. The compiler himself appears conscious of this deficiency ; for he apologizes in his preface for circumstances that have interfered with its execution. The interest attending remarkable features of nature of course remain ; but the critical merit of The Gallery of Nature is in the plan—the wide range of subject, the vast sweep of information brought before the reader in one volume. We give a specimen or two.
ANECDOTES OF BRADLEY, TIIE THIRD ASTRONOMER ROYAL.
Aberration, or wandering [of the stars] is the name given to this phrenomenon. The term is not strictly accurate, as the apparent movements thus denominated are not irregular, but uniform. To discover the physical cause became an object of intense interest to Bradley; but it long baffled his researches and reasonings, and was at length developed by an accidental circumstance. He was accompany- ing a pleasure-party in a sail on the river Thames. The boat in which they were was provided with a mast which had a vane on the top of it; it blew a moderate wind, and the party sailed up and down the river for a considerable time. Bradley remarked, that every time the boat put about, the vane at the top of the mast shifted a little, as if there had been a slight change in the direction of the wind. He observed this three or four times without speaking; at last he mentioned it to the sailors, and expressed his surprise that the wind should shift so regularly every time they put about. The sailors told him that the wind had not shifted, but that the apparent change was owing to the change in the direction of the boat, and assured him that the same thing invariably happened in all cases.
From that moment he conjectured that all the light of aberration he had observed arose from the progressive motion of light combined with the earth's ma
tion in its orbit. • This discovery established the fame of Bradley; who was exonerated from all future payments to the Royal Society on account of it: and it is of great importance, as the only sensible evidence we have of the earth's annual motion. Soon after his appointment to the Greenwich Observatory, he effected his second great discovery, that of the notation of the earth's axis,— slight oscillation of the pole of the equator about its mean place, describing. an ellipse in the period of eighteen years. He determined likewise its cause, which theory had previously inferred to be the action of the moon upon the equatorial regions of the earth. Some idea of his industry may be formed from the fact, that, in conjunction with his nephew, he made no less than eighteen thousand ob- servations in a single year while Astronomer Royal; and the number from the year 1750 to 1762 amounted to upwards of sixty thousand. The death of Brad,. ley was interpreted as a Divine judgment by the populace. He had taken an active part with the Earl of Maeclesfield and others in urging on and assimilating the British calendar to that of other nations. This rendered it necessary to throw eleven days out of the current year in the month of September 1752,—a measure which the ignorance of great numbers of the people led them to regard as an im- pious intermeddling with the Divine prerogative.
TRAITS OF MERCURY.
Mercury, the nearest planet to the Sun, is the smallest primary in the system, with the exception of the asteroids. It is the fastest traveller also; having aye- locity in space which is nearly twice the rate of the earth's orbital motion. It is the densest celestial body with which we are acquainted, supposed to be fourteen times that of water. A globe of lead, therefore, of the same volume, if weighed in the balances against its mass, would be found wanting. Yet notwithstanding this remarkable density, if loosened from the centrifugal force, it would require more than a fortnight for the planet to accomplish its dash headlong to the San. The days and nights are about the same length as our own; but a whole cycle of seasons has been four times gone through, before the Earth's spring, summer, autumn, and winter, have once revolved. Owing to his near neighbourhood to the Sun, his orb will occupy seven times more space in the Mercurian heavens than in ours, and afford a light and heat which would be intolerable to our organs without some modifying circumstances. We may, however, dismiss the idea of water always boiling at the surface, and an ever-burning heat seven times greater than the fiercest ex- perienced at our equator, distinguishing its material. The sensible heat at the different planets may depend chiefly upon their substance being more or less adapted to combine with the solar influence: there is nothing improbable, there- fore, in the supposition that the nearest may be as cool, and the remotest as warn; as the temperate zones of the Earth. Besides, it is a proud presumption to ima- gine the organism of the terrestrials to be the standard and model of finite beings. We are bound to admit that the great Author of existence can as duly attemper to every dwelling-place the physical constitution of its inhabitants as obtains with reference to our globe and its population. The volume is very handsomely printed, and profusely illustrated by copperplate scientific maps, with wood diagrams and cuts interspersed among the text.
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