NEWTON, Sir Is:A.kc (1042-1727). A failloll9 English mathematician and natural philosopher, born at Woolsthorpe, in Lincolnshire. Newton received his early education at the glummer school of Grantham, in the neighborhood of his Mpe, at Woolsthorpe. Onolune 5, 1661, he lett home for Cambridge, where he was adMitted as subsizar at Trinity College. On July sth follow ing he matriculated as sitar of the same col lege. lie immediately applied himself to mathe matical studies, and within a very few years not only made himself master of most of the works of value then existing, but had also begun to make some progress in original methods for ex tending the science. In the years 1665 and 1666 he made many important mathematical inven tions and discoveries, including that of the binomial theo•eun, the method of tangents of Gregory and Clusius, the direct method of flnxions (integral calculus), and the ac tion of gravity on the moon. According to a legend, which, however, is seriously considered by certain authorities, in the year 1665 the fall of an apple, as Newton sat in his garden at Woolsthorpe, suggested the most magnificent of Ins subsequent discove•ies—the law of universal gravitation (q.v.). On his first attempt, how ever, to apply the law, to explain the Inner and planetary motions, he employed an estimate then in use of the radius of the earth, which based on the value of a degree of latitude then prevalent, was so erroneous as to produce a dis crepancy between the value of the real force of gravity and that required by theory to explain the motions, and indicated only an approximate verification of his theory. He accordingly aban doned for a number of years the hypothesis for other studies, which consisted chiefly of investi gations of the nature of light and the construc tion of telescopes (q.v.). In 1666 he had ac quired a prism, and in 1668 completed his first reflecting, telescope, with which he observed Jupi satellites. In a variety of ingenious and in teresting experiments where a spectrum was duced by sunlight refracted through a prism in a darkened room, he 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 inapo•fection of its form, but to the fact of the different col ored rays of being brought to a focus at different distances. Be concluded rightly that it was impossible for an object-glass consisting of a single lens to produce a distinct image. Ile went further, and too hastily concluding, from a single experiment, that the dispersive power of different substances was proportional to their re fractive power, he pronounced it impossible to produce a perfect image by a combination of lenses. This conclusion—since proved erroneous
by the invention of the achromatic telescope by Chester :More Hall. about 1729, and afterwards, independently, Holland (q.v.) in 1751—turned attention to the construction of re fleeting telescopes; and the form devised by him is the one which, at later periods, proved so use ful in astronomical researches.
It was on .January II, 1672. that Newton was elected a member of the Royal Society, having become known to that body from his reflecting telescopes. and a month later his famous paper on a Theory About Light and was read before that body, in which he states that "Light consists of rays and that "Colors are not qualifications of light derived from refractions or natural bodies, as is generally believed, but original and connate properties which in divers rays are lie also said that "White light is ever mm1101111(1011 and to its composition are requisite all the afore said primary colors mixed in proper In 1675 Newton C01111111.111icated to the Itoyal So viety a paper on light and color. which contained an explanation of the production of colors by thin plates o• films, and in which were given the results of the first measurements of the col ored rings now known as rings (q!v.). Newton formulated the emission theory of light from hypotheses previously advanced by Des cartes, and a complete exposition of that theory was the iesult. All of investigations in light and color were collected into a work with the title of ptpublished in 1704. The velopment of the theory was accomplished by rigid dynamical reasoning, and the explanations of reflection, refraction, diffraction, and the colors of thin plates were made on the basis that light consisted of luminous corpuscles sent out from the light-giving body. This theory, while it did not survive the work of Young and Fresnel, nevertheless had more points in common with the undulatory theory than is generally slip posed (Optics, book ii., part iii., prop. X11.1. At what period Newton resumed his calculations about gravitation, employing the more correct measure of the earth obtained by Picard in 1670, does not clearly appear: lint it was in the year 1634 that it became known to Halley that he was in possession of the whole theory and its demon stration. It was on the urgent solicitation of Halley that he was induced to commit to a syste matic treatise these principles and their demon strations. The principal results of his discoveries were set down in a treatise called Pc .1Iot a Cor pont m , and were afterwards more completely folded in the great work entitled Philosophic(' No t u rot/is Principiu Mathenurtiea, was finally published about 16S7.