seized with a violent fever, supposed to have been brought upon him by too hard riding; and to this he fell a victim in the month of November, in the fifty-ninth year of his age. In 1808, a monument, consisting of a Doric temple enshrining his bust, was erected to his memory in Ratisbon by Charles Theodore Von Dalberg.

Kepler is represented by his biographers as a man of small stature, thin, of a weak constitution, and defective sight; but of somewhat gay and sportive manners. He was attached to his science with the most fervent enthusiasm: he sought after truth with eagerness, but forgot, in the search, the maxims of worldly prudence. To him were allotted but a scanty share of what are commonly esteemed the pleasures of life; but he endured all calamities with firmness, being consoled by the higher enjoyments which science never fails to impart to her true and cordial votaries. "As an astronomer," says Lalande, "he is as famous in astronomy for the sagacious application which he made of Tycho's numerous observations (for he was not himself an observer), as the Danish philosopher for the collection of such vast materials." To him, says another authority, the world is indebted for the discovery of the true figure of the planetary orbits, and the proportions of the motions of the solar system. Like the disciples of Pythagoras and Plato, Kepler was seized with a peculiar passion for finding analogies and harmonies in nature; and though this led him to the adoption of strange and ridiculous conceits, we shall readily be disposed to overlook these, when we reflect they were the means of leading him to the most important discoveries. He was the first who discovered that astronomers had been mistaken in ascribing circular orbits and uniform motions to the planets, since each of them moves in an ellipse, having one of its foci in the sun; and after a variety of fruitless efforts, he, on the 15th of May 1618, made his splendid discovery, that the squares of the periodic times of the planets are always in the same proportion as the cubes of their mean distances from the sun. The sagacity of this wonderful man, and his incessant application to the study of the planetary motions, pointed out to him some of the genuine principles from which these motions originate. He considered gravity as a power that is mutual between bodies; that the earth and moon tend toward each other, and would meet in a point so many times nearer to the earth than to the moon as the earth is greater than the moon, if their motions did not prevent it. His opinion of the tides was, that they arise from the gravitation of the waters towards the moon; but his notions of the laws of motion not being accurate, he could not turn his conceptions to the best advantage. prediction he uttered at the end of his epitome of astronomy, has been long since verified by the discoveries of Sir Isaac Newton; namely, that the determination of the true laws of gravity was reserved for the succeeding age, when the Author of Nature would be pleased to reveal these mysteries.

The

NEWTON.

THE year in which Galileo died, was that in which Isaac Newton was born. This eminent individual, who was destined to establish the truth of the discoveries of his illustrious predecessors, Copernicus and Galileo, was born on the 25th of December 1642, at Coltersworth, in Lincolnshire, where his father cultivated his own moderate paternal property. After receiving the rudiments of education, under the superintendence of his mother, he was sent, at the age of twelve, to the grammar school at Grantham, where the bias of his early genius was shown by a skill in mechanical contrivances, which excited no small admiration. Whilst other boys were at play, his leisure hours were employed in forming working models of mills and machinery; he constructed a water clock from an old box, which had an index moved by a piece of wood sinking as the drops fell from the bottom, and a regular dial-plate to indicate

the hours.

On his removal from school, it was intended that he should follow the profession of a farmer, but his utter unfitness for the laborious toils of such a life was soon manifested. He was frequently found reading under a tree when he should have been inspecting cattle, or superintending labourers; and when he was sent to dispose of farming produce at Grantham market, he was occupied in solving mathematical problems in a garret or hay-loft, whilst the business was transacted by an old servant who had accompanied him to town. These strong indications of the bias of his disposition were not neglected by his anxious mother; she sent him again for a few months to school, and on the 5th of June 1660 he was admitted a student of Trinity College, Cambridge.

The combination of industry and talents, with an amiable disposition and unassuming manners, naturally attracted the notice of his tutors, and the friendship of his admiring companions; amongst these was Isaac Barrow, afterwards justly celebrated as a preacher and a mathematician. Saunderson's Logic, Kepler's Optics, and the Arithmetic of Infinites by Wallis, were the books first studied by Newton at Cambridge. He read the Geometry of Descartes diligently, and looked into the subject of judicial astrology, which then engaged some attention. He read little of Euclid, and is said to have regretted, in a subsequent part of his life, that he had not studied the old mathematicians more deeply.

The attention of Newton, while he was pursuing his studies at Cambridge, was attracted to a branch of natural philosophy hitherto little understood-namely, light. It was the opinion of the celebrated philosopher Descartes that light is caused by a certain motion or undulation of a very thin elastic medium,

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which he supposed pervaded space. Newton overturned this theory. Taking a piece of glass with angular sides, called a prism, he caused the sun to shine upon it through a small hole in the shutter of a darkened apartment. By this experiment he found that the light, in passing through the glass, was so refracted or broken, as to exhibit on the wall an image of seven different tints or colours; and after varying his experiments in a most ingenious way, he established the very interesting facts, that light is composed of rays resoluble into particles, that every ray of white light consists of three primary and differentlycoloured rays (red, yellow, and blue), each of which three is more or less refrangible than the other. This remarkable discovery laid the foundation of the science of optics.

In 1665, the students of the university of Cambridge were suddenly dispersed by the breaking out of a pestilential disorder in the place. Newton retired for safety to his paternal estate; and though he lost for a time the advantages of public libraries and literary conversation, he rendered the years of his retreat a memorable era in his own existence, and in the history of science, by another of his great discoveries-that of the theory of gravitation, or the tendency of bodies towards the centre of our globe. One day, while sitting in his garden, he happened to see an apple fall from a tree, and immediately began to consider the general laws which must regulate all falling bodies. Resuming the subject afterwards, he found that the same cause which made the apple fall to the ground, retained the moon and planets in their orbits, and regulated, with a simplicity and power truly wonderful, the motions of all the heavenly bodies. In this manner was discovered the principle of gravitation, by a knowledge of which the science of astronomy is rendered comparatively perfect.

On his return to Cambridge in 1667, he was elected Fellow of Trinity College; and two years afterwards, he was appointed professor of mathematics in the place of his friend Dr Barrow, who resigned. His great discoveries in the science of optics formed for some time the principal subject of his lectures, and his new theory of light and colours was explained, with a clearness arising from perfect knowledge, to the satisfaction of a crowded and admiring audience. He was elected a Fellow of the Royal Society in 1671, and is reputed to have been compelled to apply for a dispensation from the usual payment of one shilling weekly, which is contributed by each member towards the expenses. He had at this period of his life no income except what he derived from his college and his professorship, the produce of his estate being absorbed in supporting his mother and her family. His personal wishes were so moderate, that he never could regret the want of money, except in as much as it limited his purchases of books and scientific instruments, and restricted power of relieving the distresses of others. About the year

his

1683, he composed his great work, The Principia, or Mathematical Principles of Natural Philosophy. In 1688, the memorable year of the Revolution, he was chosen to represent the university in parliament, and the honour thus conferred on him was repeated in 1701. His great merit at last attracted the notice of those who had it in their power to bestow substantial rewards, and he was appointed warden of the Mint, an office for which his patient and accurate investigations singularly fitted him, and which he held with general approbation till his death. Honours and emoluments at last flowed upon him. Leibnitz, having felt envious of the discoveries of Newton, tried to revenge himself by transmitting a problem, which he thought would show his superiority, by baffling the skill of the English mathematician. It was received by Newton in the evening, after his usual day's labour at the Mint, and he solved it before he retired to rest. After this there was no further attempt made to traduce his fame. In 1705 he received the honour of knighthood from Queen Anne.

Newton's benevolence of disposition led him to perform all the minor duties of social life with great exactness; he paid and received frequent visits; he assumed no superiority in his conversation; he was candid, cheerful, and affable; his society was therefore much sought, and he submitted to intrusions on his valuable time without a murmur; but by early rising, and by a methodical distribution of his hours, he found leisure to study and compose, and every moment which he could command, he passed with a pen in his hand and a book before him. He was generous and charitable-one of his maxims being, that those who gave nothing before death, never, in fact, gave at all. His wonderful faculties were very little impaired, even in extreme old age; and his cheerful disposition, combined with temperance and a constitution naturally sound, preserved him from the usual infirmities of life. He was of middle size, with a figure inclining to plumpness; his eyes were animated, piercing, and intelligent; the general expression of his countenance was full of life and kindness; his sight was preserved to the last; and his hair in the decline of his days was white as snow. The severe trial of bodily suffering was reserved for the last stage of his existence, and he supported it with characteristic resignation. On the 20th of March 1727 he expired at the advanced age of eighty-four years.

The character of Newton cannot be delineated and discussed like that of ordinary men; it is so beautiful, that the biographer dwells upon it with delight, and the inquiry, by what means he attained an undisputed superiority over his fellow-creatures, must be both interesting and useful. Newton was endowed with talents of the highest order; but those who are less eminently gifted, may study his life with advantage, and derive instruction from every part of his career. With a power of intellect almost

divine, he demonstrated the motions of the planets, the orbits of the comets, and the cause of the tides of the ocean; he investigated, with complete success, the properties of light and colours, which no man before had even suspected; he was the diligent, sagacious, faithful interpreter of nature, while his researches alĺ tended to illustrate the power, wisdom, and goodness of the Creator. Notwithstanding, also, his reach of understanding and knowledge, his modesty was such, that he thought nothing of his own acquirements; and he left behind him the celebrated saying, "that he appeared to himself as only a child picking up pebbles from the shore, while the great ocean of truth lay unexplored before him."

HUYGENS.

WHILE Newton, in England, was thus enlarging the boundaries of astronomy, and conferring upon it a degree of accuracy and system hitherto unknown, a number of continental philosophers were contributing materials, which, though of a humble character, was not the less necessary to the future progress of the science. First among these was Christian Huygens, Lord of Zeelhem, born at the Hague on the 14th of April 1629, and descended of a rich and respected family. His father, secretary and counsellor to the Princes of Orange, and distinguished as a scholar and poet, was not slow in observing the genius of his son, and, full of paternal solicitude for his improvement, became his first instructor. He early taught him music, arithmetic, and geography-says a writer in the Encyclopædia, from which we select the materials of this notice and initiated him, when about thirteen, in the knowledge of mechanics, for which the boy had evinced a surprising aptitude. At fifteen, he received the assistance of a master in mathematics, under whose tuition he made great progress; and at sixteen, was sent to Leyden, to study law under the eminent jurisconsult Vinnius. He did not, however, permit jurisprudence to divert him from his mathematical studies, which he now prosecuted with success, as well as afterwards at Breda, at the university of which he resided from 1646 to 1648. In these two cities he had respectively as masters two very able geometers, Francis Schooten and John Pell; and his first essays were so successful, that they attracted the notice of Descartes, to whom the author, in his admiration of that great philosopher, had communicated them. Descartes predicted his future greatness, but did not live to appreciate his discoveries.

On quitting the university, Hüygens, as was then the custom, made the tour of Europe; and after his travels, settled in his native country, where he commenced that series of inventions which have rendered his name so justly celebrated. Between