Page:The New International Encyclopædia 1st ed. v. 14.djvu/565

NEWTON. 489 NEWTON. born at Woolstliorpc, in Lincolnshire. Ncuton received lii.s early education at the grammar school of (iranthani, in the ncij;liliorliood of his home, at Woolstliorpc. On .June .">, UiOl, he left home for t'aniliridye, where he was admitted as suhsizar at Trinity College. On .July Stli follow- ing he matriculated as sizar of the same col- lege. He 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 cxi.sting, but had also begun to make some progress in original methods for ex- tending the science. In the years UiOo ami lUOO he made many important mathematical inven- tions and discoveries, including that of the binomial theorem, the method of tangents of Gregory and Clusius, the direct method of fluxions (integral calculus), and the ac- tion of giavity on the moon. According to a legend, which, however, is scrious-ly consitlered by certain authorities, in the year 16G5 the fall of an apple, as Xewton sat in his garden at W'oolsthorpe, suggested the most magniticent of his subsequent discoveries — the law of universal gravitation (q.v.). On his first attempt, liow- ever, to apply the law, to explain the lunar 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 stiulies, which consisted chicily of investi- gations of the nature of light and the construc- tion of telescopes (q.v.). In ICGG he had ac- quired a prism, and in 1G68 completed his first reflecting telescope, with which he observed Jupi- ter's satellites. In a variety of ingenious and in- teresting experiments where a spectrum was pro- duced by sunlight refracted through a prism in a darkened room, he was led to the conclusion that rays of light which difTer in color difi'er 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 diflercnt col- ored rays of light being broiight to a focus at difYcrent 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 the dispersive power of difl'erent substances was proportional to their re- fractive power, be pronounced it impossible to produce a perfect image by a comliination of lenses. This conclusion — since proved erroneous by the invention of the achromatic telescope by Chester ilore Hall, about 1720. and afterwards, independently, by Dolland (q.v.) in 17.51 — turned Newton's attention to the construction of re- flecting 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 11. 1(172, 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 "New Theory About Light and Color" was read before that body, in which he states that "Light consists of rays dilVerently refrangible" and that "Colors are not (lualilieations of light derived from refractions or natural bodies, as is generally believed, but original and connate ])roperties which in divers rays are divers." Ho also said that "White light is ever compounded and to its composition are recpiisite all the afore- said primary colors mixed in proper proportion." In 1075 Newton connnunicated to the Royal So- ciety a paper on light and color, which contained an explanation of the production of colors by thin plates or films, an<l in which were given the results of the first measurements of the col- ored rings now known as Newton's 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 result. All of Newton's investigations in light and color were collected into a work with the title of Oplictn, published in 1704. The de- velopment of the theory was accomplished l)y rigid dynamical reasoning, and the explanation.s of reflection, refraction, diffraction, and the colors of thin ])lates 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 Voung and Fresnel, nevertheless had more points in connuon with the undulatory theory than is generally sup- posed {Optics, book ii., part iii., prop. XI I.). At what period Newton resumed his calculations about gravitation, employing the more correct measure of the earth obtained by Picard in lti70, does not clearly appear; but it was in the year 1684 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 w'as 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 Dr Motii Cor- porum, and were afterwards more conii)lctely un- folded in the great work entitled FhihisiijihitB Saturalis Piviicipia Mnlhemuticn, which was finally pfl)lished about midsununer, I0S7. Shortly before the Principi/i was given to the public, Newton, who since 1(560 had occupied the Lucasian chair at Cambridge, was called to take an active part in defending the rights of the university against the illegal encroachments of .James II. The conspicvu)us part which he had taken on that occasion procured him a seat in the Convention Parliament, in which he sat from January, 1680. to its dissolution in ICiOO. In 1606 he was appointed warden of the mint, and in 1600 was promoted to the oflice of master of the mint, an ollice which he held till the end of his life. He again took a seat in Parliament in the year 1701, as the representative of his university. Thus engaged in the public service, he had little time left for mere scientific studies — pursuits which he always held of secondary iuqiortance to the public duties in which he was engaged. In the interval of public duly, how- ever. Newton showed that lie still retained the scientific power by which his great discoveries had been made. He was president of the Royal Society from 1703 till his death, a period of twenty-four years, being each year reelected. In this position, and enjoying the confidence of Prince George of Denmark, he did much toward the advancement of science; and one of his most