Mr. Newton's first discoveries respecting the Colours of Light, which appeared in the Philosophical Trans actions for 1671, did not experience that reception to which they Were entitled. Father Pardics published attacks upon the new doctrines; but, after two re plies from Me. Newton, the Cartesian philosopher aban doned the field. An anonymous Frenchman, AI. N. re vived the controversy in 1673, and when two papers had appeared on each side, the discussioo was dropped. Father Lucas, and his pupil Al. Gascoigne, followed in thc same route of ignolant opposition to incontroverti ble lam. NI. Lucas of Liege opposed the theory even after repeating the experiments; hut Newton, who re plied to every animadversion that was made upon his opinions, finally triumphed over all his enemies, and left his Doctrine of Light and Colour as an imperish able monument of his industry and genius.
But though our author had the high satisfaction not only of knowing the soundness of his doctrines, but of seeing them universally received by those who could understand them, it was mingled with feelings of no very agreeable kind. The mean jealousies, both private and national, which had shown themselves during a contro versy of four ycars continuance, made a deep impression on his candid and upright mind. He had no doubt ima gined, under the influence of his own noble zeal for science, that new truths would meet with a weluome reception from all who bore the name of philosophers ; and his surprise was great indeed when he made the only one of his discoveries which was truly mortifying to him, that the petty jealousies of vulgar life had often a deep root in minds which education and knowledge ought to have elevated and ennobled. So deep indeed was his mortification, that, in his preface to his Optics, lie says, that in order " to avoid being engaged in disputes about these ir.atters, I have hitherto delayed the printing, and should still have delayed it, had not the importunity of friends prevailed on me." Hc seems indeed to regret that he took any part in the contioversy, when he says, " I blamed my own imprudence for parting with so real a blessing as my quiet, to run alter a shadow." In the winter of 1676 and 1677, he discovered the ce lebrated proposition, that by a centripetal force, varying in the inverse ratio of the distance, a planet will de scribe an ellipse about the centre of force placed in the lower focus, and that the radius vector will describe areas proportioned to the lines.
In the year 1630, Alr Newton made numerous ob servations on the comet, and. contrary to the opinion of Mr. Flanistead, he supposed that there were two differ ent comets. Upon receiving a letter from Air. Hook, explaining the nature of the line described by a falling body, supposed to be moved circularly by the diurnal motion of the earth, and perpendicularly by the power of gravity, he was led to inquire into the real cubit of such a body. in the course of thc inquiry, he resumed his forrner spe culations respecting the moon ; and as Picard had, in 1679, measured a degree of the earth with considerable accuracy, lie proceed( d upon better data, and found that the moon was actually retained in her orbit by the power of gravity, and that this power decreased in the duplicate ratio of the distance. Hence he found that the line described by a falling body was an ellipse, having one of its foci in the earth's centre. In
this manner was Newton led to the consideration of the planetary motions ; and when Dr. Halley was at Cam bridge about the end of 1684, lie showed him a treatise De Motu. Corporunz, which he promised to send to the Royal Society to be entered in their register Dr. Hal ley mentioned these particulars to the Royal Society at their meeting on the 18th December, 1689, and he was desired, along with Mr. Paget, to put AIr. Newton in mind ol his promise. In a letter dated the 25th of Fe bruary, Mr. Newton signified his willingness to enter in their register his opinions about motion; and he seems to have spent the remainder of that year, and the whole of 1685, in arranging his various discoveries respecting the law of gravity and the planetary motions. On the 18th of April, 1686, he accordingly presented to the Royal Society, through Dr. Vincent, a manuscript trea tise, entitled, Philosophic Araturalis Principia llfathema tica, dedicated to the Society. in which, as the minute states," he gives a mathematical demonstration of the Copernican hypothesis, as proposed by Kepler, and makes out all the phenomena of the celestial motions by the only supposition of a gravitation towards the cen tre of the sun, decreasing as the square of the distance therefrom reciprocally." On the 19th Alay, it was or dered " that Mr. Newton's book be printed forthwith in a 4to. of a fair letter; and that a letter be written to him to signify the Society's resolution, and to desire his opinion as to the print, volume, cuts, 8tc." On the 2r1 June, it was again ordered " that Air. Edmund Halley shall undertake the business of looking after it, and printing it at his own charge, which he engaged to do." This great work accordingly appeared under the above mentioned title about midsummer, 1637; but it did not at first receive that applause which it so well merited. From the universal prevalence of the Cartesian philoso phy, on the one hand, and the mathematical acquirements which Were necessary to understand the profound inqui ries which the Principia contained, it was introduced slowly into notice. The triumph, however, of the new philosophy was sure in proportion to the slowness of its march ; and when its value became generally known, it acquired for its author a brilliancy of reputation which had never before fallen to the lot of man. " Does Mr. Newton eat, drink. or sleep, like other men ?" said the Marquis de l'llospital to the English who visited him : " I represent him to myself as a celestial genius, en tirely disengaged from matter." In the year 1687, king James II. sent a mandamus to the University of Cambridge, to achnit father Francis, an ignorant Benedictine monk, to the (levee of M. A. This unwarrantable encroachment on the privileges of the university was strenuously resistcd by its leading members, and Mr. Newton was appointed one of the delegates to the high commission court, where the uni versity maintained its rights with such resolution and steadiness, that the king found it advisable not to press the matter any faither. Mr. Newton was in 1688 cho sen one of the /representatives of thc University, in the corvention parliament, which he regulatly attended till its chssollition.