NEWTON, Sir ISAAC, the most remarkable mathematician and natural philosopher of his own or perhaps of any other age, was b. at Woolsthorpe, hi Lincolnshire, in the year 1642. That year, remarkable in English history for the breaking out of the civil war between Charles I. and the parliament, is doubly remarkable in the history of science by the birth of Newton and the death of Galileo. The circumstances with which the pursuit of truth, in scientific matters, was at this time surrounded in the respective coun tries of these great philosophers, were not more different than the characters of the phi losophers themselves. Galileo died a prisoner, under the surveillance of the inquisition, "for thinking, in astronomy." as Milton says, "otherwise than the Franciscan and Dominican licensers thought." In England. it had become the practice, and soon became the fashion, through the influence of Bacon and Descartes. to discard altogether the dic tates of authority in matters of science. The dispositions of the two philosophers were happily suited to the situations in which they thus found themselves. Galileo's was a mind whose strength and determination grew by the opposition it encountered. The disposition of Newton on the other hand, diffident of the value and interest of his own labors, and shrinking from the encounter of even scientific controversy, might have allowed his most remarkable discoveries to remain in obscurity had it not been for the constant and urgent solicitation of his friends that they should he published to the world.
Newton received Ids early education at the grammar school of Grantham, in the neighborhood of his home, at Woolsthorpe. On June 5, 1661, he left home for Cam bridge, where he was admitted as subsizar at Trinity college. On July 8 following, he matriculated as siza• of the same college. He immediately applied himself to the mathe matical studies of the place, and within a very few years must have not (W. v made him self master of most of the works of any value on such subjects then existing, but had also begun, to make some propTess in the :nethods for extending the science. In the year 1665 he committed to writing his first discovery on flexions; and it is said that in the same year, the fall of an apple, as he sat in his garden at Woolsthorpe, suggested the most magnificent of his subsequent discoveries—the law of universal ,gravitation. On
his first attempt, however, by mesas the.lawso suggested to his mind, to explain the lunar and planetary./ Imitions;ho einPloYlid an eatimate then itruse:of the radius of the earth, which was so erroneous as to produce is discrepancy between the real fon>a of gravity and that required by theory to explain the motions, corresponding to the respec tive figures 16.1 and 13.9. He accordingly abandoned the hypothesis for otherstudies. These other pursuits to which he thus betook himself, consisted chiefly of investigations into the nature of light, and the construction of telescopes. By a variety of ingenious and interesting experiments upon sunlight refracted through a prism in a darkened apartment, lie was led to the conclusion that rays of light which differ in color, differ also in refrangibility. This discovery enabled him to explain an imperfection of the telescope, which had not till then been accounted for. The indistinctness of the image formed by the object-glass was not necessarily due to any imperfection of its form, but to the fact of the different colored rays of light being brought to a focus at different distances. He concluded rightly that it was impossible for an object-glass consisting of a single lens to produce a distinct image. He went further, and too hastily concluding, from a single experiment, that t he dispersive power of different substances was pro portional to their refractive power, he pronounced it impossible to produce a perfect image by a combination of lenses. This conclusion—since proved erroneous by the dis covery of the acromatic telescope by Mr. Chester More Hall, of More Hall, in Essex, about 1729, and afterwards, independently, by Mr. Dollond in 1731—turned Newton's attention to the construction of reflecting telescopes; and the form devised by him is the one which, at later periods, reached such perfection in the hands of sir William Her schel and lord Bosse.