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haps, be illustrated by a work on corpuscular mechanics, bearing the same relation to these primary discussions of Laplace, that the Mecanique Celeste does to the Principia of Newton.
Wherever we have had occasion to speak of the progress made in any of the branches of celestial mechanics, Newton has presented himself to us as the first inquirer, and we have in some cases seen him making vast and even marvellous progress. · He was in truth, in this department of knowledge, far in advance of the spirit of the age in which he lived. Astonished at his progress, or envious of his honours, his contemporaries took no part in the mighty labour, and fifty years elapsed between Newton's publication of the Principia, and the time of Clairaut, nay, near seventy from the discovery of the law of gravitation, before one important addition was made to the investigations of Newton. Instances of this sort are rare in the history of man. Archimedes is another similar case, but he was even more widely removed from the bounded sphere of his contemporaries, for no addition was made to his discoveries in the theory of mechanics, until the time of Galileo. The last named philosopher was on the other hand one of a brilliant constellation that spread a sudden light over Europe, and left pupils who rapidly extended his discoveries.
But although Newton thus amazed, or excited the envy of his contemporaries, until they either feared, or refused to enter into competition with him, the age was not unprepared for his discoveries; it may even be considered probable that the theory of universal gravitation, and its consequences, could not have remained much longer hidden. We have in another place mentioned how closely Kepler approached the point attained by Newton,* but a single false step prevented him from anticipating Newton in laying the foundation of the mechanics of the heavens. In his introduction to his work de Stella Martis, as quoted by Laplace in his Exposition du Systeme du Monde, he thus expresses his views in relation to gravity :
“Gravity is no more than a corporeal and mutual affection between bodies.
“The direction of the gravity of bodies is not towards the centre of the world, but towards that of the round body of which they form a part; and if the earth were not spherical, heavy bodies placed at different points on its surface would not fall towards the same centre.
“Two isolated bodies would approach each other, like two magnets, passing over, in order to meet, spaces inversely as their masses. If the earth and the moon were not retained, at the distance which separates them, by an animal force or something equivalent, they would fall one upon the other, the moon performing of the distance, and the earth the rest, supposing them to be both equally
dense. “If the earth should cease to attract the waters of the ocean they would be carried towards the moon, in consequence of the attractive force of that body.
* 4'm. Quar. No. VI. p. 295.
“This force which reaches to the earth produces there the phenomena of the Aux and reflux of the tides. "
But these beautiful and correct views are mixed up with much absurdity and hypothesis, from which his cotemporaries and successors knew not how to separate them. He himself stopped short in the middle of the career he had entered upon, and even in his latest works appears to have laid as much stress upon fantastic views of the theory of numbers, and the necessity of the universe being subject to the laws of musical harmony, as upon the just and clear views we have cited above.
Other steps had been also made, equally suited as preparations for the investigations of Newton. Descartes had shown how mathematics might be applied to mechanical philosophy, and although his discussions are in themselves useless in consequence of faulty and absurd hypotheses, the example was not the less valuable in pointing out how similar methods might be applied to true theories. The method of maxima and minima and that of tangents invented by Format had laid the foundations of the infinitesimal calculus; Wallis, Wren, and Huygens had just discovered the laws of motion; the last named philosopher, had, in his theory of centrifugal force, led the way to the consideration of curvilinear motion; and Leibnitz was on the very eve of the invention of a method similar to that employed by Newton himself in his researches. But one thing was in truth wanting to render all these isolated inventions applicable to the theory of the universe, and this was, that the law which governed the action of the mutual attraction of the planets, should be attained. Newton however does not appear to have known, or at least to have been satisfied with the views of Kepler in relation to the mutual action of gravity, while the law that Kepler had assigned for its decrease is obviously false. The scene of his first inquiry into this subject is usually laid in a garden at Cambridge, but in the letter written by his nephew Conduitt to Fontenelle, the occurrence is said to have happened in the garden of his paternal estate of Woolsthorpe, and in Turner's History of the Town and Soke of Grantham, published in 1806, the apple-tree whose falling fruit gave rise to the inquiry is still said to exist.
The mental process by which he extended the cause, that makes a heavy body fall to the earth's surface, to the circumstances of the moon's motion, is familiar to all, as well as the instantaneous grasp he took of the true law of its action; while the modesty with which he submitted to lay aside this splendid theory, when he found it inconsistent with what was then known of the magnitude of the earth and the distance of the moon, is perhaps as characteristic of a great mind as the discovery itself. The subject was again up taken under more fortunate auspices, after VOL. V.-NO. 10.
the publication of Picard's measure of a degree of the meridian, and was developed in the immortal Principia.
A synopsis of the extent to which he carried his investigations of the necessary consequences of his theory, although we have already had occasion to state some of them, and shall, in our succeeding article, refer to the rest, will not be out of place. To unite them in one view, will give a better means of estimating the powers of Newton, than the separate discussion of each under its appropriate head.
1. He found these remarkable properties of the mutual attraction of the particles of bodies: that the attractive force of a sphere, or of a spherical shell, is the same as if its mass were collected in its centre; and that a point placed within a spherical or elliptical shell, is equally attracted on all sides.
2. He proved the rotation of the earth must cause it to be flattened at the poles; and he determined the laws of the variation of degrees of a meridian, and of the intensity of gravity, on the hypothesis of the earth's being homogeneous.
3. He saw that the action of the sun and moon on the terrestrial spheroid, must produce an angular motion in its axis of rotation, cause the equinoctial points to fall back, lift up the waters of the ocean, and keep up the oscillations in the fluid mass, which we call the tides.
Of these, he completed the theory of the attraction of spherical bodies, and left nothing further to be done by his successors; so also the problem of the mutual attraction of two bodies causing the elliptic motion of the planets, and the examination of the intensity of the attractive force of the sun, and of planets accompanied by satellites, leave nothing to be desired. But the other subjects are merely presented in outline. His theory of the figure of the planets, is limited to a single case; his solution of the problem of the precession of the equinoxes is imperfect; and he has considered the perturbations of no other body but the moon, one of the most important of which escaped his view entirely. Still, however, he succeeded in establishing, beyond question, the truth of the principle he had discovered. To have detected it, and placed its evidence upon incontrovertible grounds, entitle him to claim a station among philosophers the most exalted. It is the peculiar glory of the Newtonian philosophy, that its extension, is limited by the bounds of the universe alone, and its application, by our power of becoming acquainted with the existence of bodies. If its applications to the solar system have been finally exhausted by Laplace; the phenomena of the double stars, and the probability which daily becomes more strong, that the stars themselves move according to the great law of universal gravitation, open new fields for extending it to the explanation of phenomena, upon a scale exceeding those observed in
our system, as much, or far more, than that system exceeds in magnitude our own earth.
It is this vast extent of application, of which the theory of Newton is susceptible, and its having been the basis of all the discoveries made in celestial mechanics, which entitle his Principia to deserved pre-eminence over every uninspired production of human genius.
But in elevated science, works of even the most exalted character soon cease to excite interest, and in this respect stand upon a footing far less favourable than those which treat of the mere elements, or than the productions of literary genius. In elementary science, however difficult the first formation of the path may have been, when once it is fairly beaten, it becomes the only practicable passage. In literature, the state of the language forms the only limit of the excellence to which a single author of exalted genius may at once attain, unaided by his predecessors, and without the risk of being surpassed by posterity. The first book of Euclid's Geometry, is, after more than twenty centuries, superior, in all the essential requisites, to any other treatise ; while the poems of Homer maintain a pre-eminent rank among literary productions. It is not so with the researches of this elevated science; the subject is vast as creation itself, and its improvement is due to the labours of successive generations. However perfect a work may be at first, it will, generally speaking, serve only as the point whence to proceed to new discoveries, and thus prepares the
way for works that will condemn itself to oblivion. Such cannot be the case with the Principia ; its value can never be forgotten; it will always be consulted by the curious inquirer, but its use at the present day, in a course of the study of celestial mechanics, is in a great measure at an end.
We have spoken of a letter written by Newton's nephew, and successor in the office of master of the mint, to Fontenelle, when the latter was engaged in preparing his eulogium. It was first published in the year 1806, in a history of the town of Grantham, by Edmund Turner, F. R. S. There are also in it other particulars in respect to the early life of this great man, in a letter from Dr. Stukely to Dr. Mead.
Newton's attention, it appears, was originally drawn to mathematics, in any thing but the legitimate mode of study. Desiring to know the grounds of judicial astrology, at an early age, he erected a figure, and as in this some geometric problems are necessary, he looked for those he wanted in the Elements of Euclid, by the aid of the index. Thence,
"He went at once upon Descartes' Geometry, and made himself master of it, by dint of genius and application, without going through the usual steps, or having the assistance of any other person.'
In 1664, being then twenty-two years of age, he obtained a prism, and made the discoveries that form the basis of his theory of optics; about the same time, he seems to have discovered his method of Auxions. In 1665, he first obtained the law of the decrease of the attraction of gravitation, in the detection of which he was probably aided by his previous experiments on light, the decrease of whose intensity follows the same law with that of gravity. Thus he had laid the foundation of all his reputation, at the early age of twenty-three years.
The earnestness with which Conduitt urges upon Fontenelle to take particular notice of the favour Newton enjoyed with Queen Caroline, the wife of George II., is curious. At this distance of time, when the fame of Newton fills the whole world, and when Queen Caroline is better known to us by the space she occupies in the “Heart of Mid-Lothian," and the gossiping Reminiscences of Horace Walpole, than by her importance in real history; we can hardly believe, that one who admired and respected his great relative, as cordially as Mr. Conduitt seems to have done, could have thought this to be an addition to his fame.
In the letter from Dr. Stukely, it appears, that when at the grammar school of Grantham, he employed the time devoted by his school-fellows to play, in the construction of machines, among which a clock and a windmill were particularly remembered.
When he was of the age of fourteen, his mother removed him from the school, with the view of making him useful on her farm. Among other tasks, he was often sent in company with a trusty servant to the market at Grantham, to sell corn, and other commodities. But Newton on these occasions either retired until the business was performed, to a garret, in which lay a pile of books, or else stopped upon the road, and amused himself with a book under the shade of a hedge, until the servant returned. The farming business at home was no better attended to.
“ Likewise, when at home, if his mother ordered him into the fields, to look after the sheep, the corn, or any other rural employment, it went on very heavily through his manage. His chief delight was to sit under a tree with a book in his hands, or to busy himself with his knife in cutting wood for models of somewhat or other that struck his fancy: or he would get to a stream, and make mill-wheels."
Such amusements, at such an age, were probably considered as childish ; they at least convinced his mother that he was unfit for a farmer; he was returned to the grammar school, and thence transferred in due time to the University of Cambridge. Yet was he not of that abstract turn of mind which disqualifies for the active business of life; he held for many years the important public oflice of master of the mint, in which he gave the greatest