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by his undivided devotion to science, is equally probable.

      On July 8, 1661, Newton entered college, and soon, through the study of Descartes' Geometry, showed his skill in higher mathematics. And now began an almost unexampled development of mind.

      At twenty-two, he was studying a comet so closely, and the circles and halo round the moon, that he impaired his health by sitting up late at night. In 1665, May 20, when he was twenty-three, he committed to writing his first discovery of fluxions – "the infinitely small increase or decrease of a variable or flowing quantity in a certain infinitely small and constant period of time."

      The same year, when the college had been dismissed on account of the plague in Cambridge, Newton made his immortal discovery of the Attraction of Gravitation. While sitting alone in his garden at Woolsthorpe, and observing an apple fall to the ground, it occurred to him that as the same power by which the apple fell was not sensibly diminished at the summits of the loftiest spires, nor on the tops of the highest mountains, it might extend to the moon, about which he had been studying, and retain her in her orbit. If to the moon, why not to the planets?

      The tree from which the apple fell was so much decayed in 1820, that it was cut down, but the wood was carefully preserved by Mr. Turnor of Stoke Rocheford.

      In the beginning of the following year, 1666, when Newton was twenty-four, he purchased a prism, in order to make some experiments on Descartes' theory of colors. He made a hole in his window shutter, darkened the room, and admitted a ray of the sunlight. On the opposite wall he saw the solar or prismatic spectrum, an elongated image of the sun, about five times as long as it was broad, and consisting of seven different colors; red, orange, yellow, green, blue, indigo, and violet. White light was thus discovered to be of a compound nature; a mixture of all the colors. He said, "Whiteness is the usual color of light; for light is a confused aggregate of rays endued with all sorts of colors, as they are promiscuously darted from the various parts of luminous bodies." If any one color predominates, the light will incline to that color, as the yellow flame of a candle. Heretofore, there had been all sorts of conjectures about the nature and origin of colors. Descartes believed them to be a modification of light, depending on the direct or rotary motion of its particles. But Newton showed by many experiments that color is a property of light, or innate in light itself. We speak of a thing as red because it reflects red, and absorbs all the other colors. The green leaf stops or absorbs the red, blue, and violet rays of the white light, and reflects and transmits only those which compose its green.

      He also found that the red rays are refracted or turned out of their course least of all the colors, and violet most, thereby discovering the different refrangibility of the rays of light; "a discovery which has had the most extensive applications to every branch of science, and, what is very rare in the history of inventions, one to which no other person has made the slightest claim."

      His beautiful experiments with rings resulted in his Scale of Colors, of great value in optical research.

      In 1668, when Newton was twenty-six, he constructed a small reflecting telescope, and soon a larger one, which he sent to the Royal Society; and was made a member of that body, in 1671. Two years previously he had been appointed to the Lucasian professorship of mathematics at Cambridge.

      He was now, at twenty-seven, spoken of as a man of "unparalleled genius." He had discovered the compound nature of white light, the attraction of gravity, fluxions, and made the first reflecting telescope ever directed toward the heavens, though one had been invented previously, by James Gregory, of Aberdeen. The boy who had thought of a mouse to turn his windmill had thought out some of the sublimest things in nature, and was henceforward to rank as one of the few masterminds of science. Newton's doctrine of colors met with the most bitter opposition. At last, he became so tired of the controversy, that he wrote Leibnitz, "I was so persecuted with discussions arising out of my theory of light, that I blamed my own imprudence for parting with so substantial a blessing as my quiet to run after a shadow." To another he wrote, "I see I have made myself a slave to philosophy; but if I get free of Mr. Linus's business, I will resolutely bid adieu to it eternally, excepting what I do for my private satisfaction, or leave to come out after me; for I see a man must either resolve to put out nothing new, or to become a slave to defend it."

      Newton was also troubled pecuniarily at this time, and asked to be excused from the weekly payments to the Royal Society, thereby resigning his membership. He even meditated the study of law, as his income was so limited. Strange that so many of the great things of this life are wrought out by those who are in sorrow or privation.

      But amid all the opposition to his discoveries and his poverty, the unparalleled devotion to study was continued. When he was weary of other branches, he said "he refreshed himself with history and chronology." Years afterward he published the "Chronology of Ancient Kingdoms amended, to which is prefixed a short chronicle, from the first memory of things in Europe, to the Conquest of Persia, by Alexander the Great." Says a gentleman who was with him for years, "I never knew him to take any recreation or pastime, either in riding out to take the air, walking, boating, or any other exercise whatever, thinking all hours lost that were not spent in his studies, to which he kept so close that he seldom left his chamber except at term time, when he read in the schools, as being Lucasianus Professor, where so few went to hear him, and fewer that understood him, that oftentimes he did in a manner, for want of hearers, read to the walls…

      "So intent, so serious upon his studies that he ate very sparingly, nay, ofttimes he has forgot to eat at all, so that, going into his chamber, I have found his mess untouched, of which when I have reminded him he would reply, 'Have I?' and then making to the table, would eat a bit or two standing, for I cannot say I ever saw him sit at table by himself. At some seldom entertainments the masters of colleges were chiefly his guests.

      "He very rarely went to bed till two or three of the clock, sometimes not till five or six, lying about four or five hours, especially at spring and fall of the leaf, at which times he used to employ about six weeks in his elaboratory, the fire scarcely going out either night or day, he sitting up one night, and I another, till he had finished his chemical experiments, in the performances of which he was the most accurate, strict, exact…"

      When his most intense studies were carried on, "he learned to go to bed at twelve, finding by experience that if he exceeded that hour but a little, it did him more harm in his health than a whole day's study."

      "He very rarely went to dine in the hall, except on some public days, and then if he has not been minded, would go very carelessly, with shoes down at heels, stockings untied, surplice on, and his head scarcely combed… At some seldom times when he designed to dine in the hall, he would turn to the left hand and go out into the street, when making a stop when he found his mistake, would hastily turn back, and then sometimes, instead of going into the hall, would return to his chamber again… In his chamber he walked so very much that you might have thought him to be educated at Athens, among the Aristotelian sect."

      So absent-minded was he, the story is told of him, that going home to Colsterworth, he led his horse up a hill. When he designed to remount, the animal had slipped the bridle and gone away unperceived, though Newton held the bridle in his hand all the time. He would often sit down on his bedside after he rose, and remain there for hours without dressing, so completely absorbed was he in his thought. How few in all this world have been so devoted to science! And yet how many expect success without this devotion!

      The same gentleman writes of Newton, "His carriage was very meek, sedate, and humble, never seemingly angry, of profound thought, his countenance mild, pleasant, and comely. I cannot say I ever saw him laugh but once."

      In 1687, when Newton was forty-five, his Philosophiæ Naturalis Principia Mathematica was published. "The Principia consists of three books. The First Book, besides the definition and axioms, or laws of motion, with which it begins, consists of fourteen sections, in the first of which the author explains the method of prime and ultimate ratios used in his investigations, and which is similar to the method of fluxions. The other sections treat of centripetal forces, and motions in fixed and movable orbits.

      "The Second Book consists of nine sections, and treats of bodies moving in resisting media, or oscillating as pendulums.

      "The Third Book consists of five sections,

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