rarified light, as in bodies which consist of white and black particles arranged alternately. _Green_ is nearly allied to blue. _Yellow_ is a mixture of much white and a little red; and _Purple_ consists of a great deal of blue mixed with a small portion of red. The blue colour of the sea arises from the whiteness of the salt which it contains, mixed with the blackness of the pure water in which the salt is dissolved; and the blueness of the shadows of bodies, seen at the same time by candle and daylight, arises from the whiteness of the paper mixed with the faint light or blackness of the twilight. These opinions savour so little of genuine philosophy that they must have attracted the observation of Newton, and had he discovered at that time that white was a mixture of all the colours, and black a privation of them all, he could not have permitted the absurd speculations of his master to pass uncorrected. That Newton had not distinguished himself by any positive discovery so early as 1664 or 1665, may be inferred also from the circumstances which attended the competition for the law fellowship of Trinity College. The candidates for this appointment were himself and Mr. Robert Uvedale; and Dr. Barrow, then Master of Trinity, having found them perfectly equal in their attainments, conferred the fellowship on Mr. Uvedale as the senior candidate. In the books of the university, Newton is recorded as having been admitted sub-sizer in 1661. He became a scholar in 1664. In 1665 he took his degree of Bachelor of Arts, and in 1666, in consequence of the breaking out of the plague, he retired to Woolsthorpe. In 1667 he was made Junior Fellow. In 1668 he took his degree of Master of Arts, and in the same year he was appointed to a Senior Fellowship. In 1669, when Dr. Barrow had resolved to devote his attention to theology, he resigned the Lucasian Professorship of Mathematics in favour of Newton, who may now be considered as having entered upon that brilliant career of discovery the history of which will form the subject of some of the following chapters. CHAPTER III. _Newton, occupied in grinding Hyperbolical Lenses—His first Experiments with the Prism made in 1666—He discovers the Composition of White Light, and the different Refrangibility of the Rays which compose it—Abandons his Attempts to improve Refracting Telescopes and resolves to attempt the Construction of Reflecting ones—He quits Cambridge on account of the Plague—Constructs two Reflecting Telescopes in 1668, the first ever executed—One of them examined by the Royal Society, and shown to the King—He constructs a Telescope with Glass Specula—Recent History of the Reflecting Telescope— Mr. Airy’s Glass Specula—Hadley’s Reflecting Telescopes—Short’s— Herschel’s—Ramage’s—Lord Oxmantown’s._