the years 1650-60, his pursuits were chiefly mathematical, resulting in several publications of acknowledged merit. In 1655 he travelled into France, and took the degree of Doctor of Laws at Angers; and in 1658 made known his invention of the pendulum clock. In the following year he published his discoveries relative to the planet Saturn; discoveries which inseparably associate his name with the science of astronomy. Galileo had endeavoured to explain some of the appearances exhibited by that planet. He had at first observed two attendant stars, but some time afterwards was surprised to find that they had disappeared. Huygens, desirous to account for these changes, laboured with his brother Constantine to improve the construction of telescopes; and having at length made an instrument of this kind, possessing greater power than any which had yet been contrived, he proceeded to observe the phases of Saturn, and to record all the different aspects of that planet. The results were of equal interest and importance to the science of astronomy. He discovered a satellite of that planet which had hitherto escaped the notice of astronomers; and after a long course of observation, he showed that the planet is surrounded by a solid and permanent ring, which never changes its situation. In 1660 he took a second journey into France; and the year following he visited England, where he communicated the art of polishing glasses for telescopes, and was admitted a member of the Royal Society. The air-pump, then recently invented, he materially improved; and about the same time he also discovered the laws of the collision of elastic bodies, as did afterwards our own countrymen Wallis and Wren, who disputed with him the honour of the discovery. After a stay of some months in England, Huygens returned to France, where, in 1633, his merit became so conspicuous, that Colbert resolved to bestow on him such a pension as might induce him to establish himself at Paris. This resolution was not carried into effect until 1665, when letters in the king's name were written to the Hague, where the philosopher then resided, inviting him to repair to Paris, and offering him a considerable pension, with other advantages. Huygens accepted the proposal; and from 1666 to 1681, settled at Paris, where he was admitted a member of the Royal Academy.

During this period he was chiefly engaged in mathematical pursuits he wrote and published several works, which were favourably received; and he invented and improved some useful instruments and machines. By continued application, his health began to be impaired, and he at length found it necessary to return to his native country-a step somewhat accelerated by the revocation of the Edict of Nantes, which rendered him liable to molestations, although assured of the fullest privilege to follow his own religious opinions. He accordingly left the French metropolis in 1681; passed the remainder of his days in his own

country, and in the pursuit of his favourite subjects; and died at the Hague on the 8th of June 1683, in the sixty-seventh year of his age. "This illustrious man," continues our authority, gave his whole time to science; he loved a quiet studious life, and found sufficient enjoyment in pursuing curious and useful researches. He was modest, amiable, cheerful, and in all respects as estimable in private life as he was eminent in science. It is not a little singular that the discovery of the real nature, or at least of the true figure, of the luminous ring which encompasses the planet Saturn, should have been made by the same individual who invented the pendulum clock and the micrometer." His inventions, however, were more of a mathematical and mechanical than of an astronomical character; and we safely predict, that had Hüygens lived in the present day, he would have risen to superlative fame as a mechanician and engineer.

HALLEY.

Dr Edmund HALLEY, a name well known in the annals of astronomy, was the only son of a soap-boiler in London, and was born in 1656. He received the rudiments of his education at St Paul's School in his native city; and in his seventeenth year, became a commoner in Queen's College, Oxford. At first he applied himself to the study of the languages and sciences, but at length gave himself wholly up to that of astronomy; and before he had attained his nineteenth year, published a method of finding the aphelia and eccentricity of planets, which supplied a defect in the Keplerian theory of planetary motions. By some observations on a spot on the sun's disk in the summer of 1676, he established the certainty of the motion of that body round its own axis; and in the same year fixed the longitude of the Cape of Good Hope, by his observation of the occultation of Mars by the moon. Immediately after, he went to St Helena, where he stayed till 1678, completing a catalogue of the fixed stars of the southern hemisphere, which was published in the following year, and gained for its author the appellation of the "Southern Tycho.' In 1679 he was called upon to settle a dispute between the English philosopher Hooke and the celebrated Hevelius, respecting the use of optical instruments in astronomy, and for this purpose went to Dantzic, where, with honourable impartiality, he decided against his own countryman. In 1680 he made the tour of Europe, making the acquaintance of Cassini at Paris, and completing his observations from the Royal Observatory of France on the comet which now bears his name. After spending the greater part of 1681 in Italy, he returned to England, and settled at Islington, where he fitted up an observatory for his astronomical researches.

In 1683 he published his Theory of the Variation of the Mag

netical Compass, in which he endeavoured to account for the phenomenon, by the supposition of the whole globe being one great magnet, having four circulating magnetical poles or points of attraction. His theory, though unsatisfactory, is ingenious. The doctrines of Kepler relative to the motions of the planets next engaged his attention; and finding himself disappointed in his endeavours to obtain information on the subject from Hooke and Sir Christopher Wren, he went to Cambridge, where Newton, then mathematical professor, satisfied all his inquiries. In 1691 he was candidate for the Savilian professorship of astronomy at Oxford-a chair which he would have obtained, had he not refused to profess his thorough belief in all the doctrines of the Christian religion, as taught by the church of England. For the purpose of making further observations relative to the variation of the compass, he set sail on a voyage in 1699 (having obtained the command of a vessel from King William, who was anxious to promote the cause of geographical and astronomical science); and after traversing both hemispheres, and making important observations at numerous stations, he returned to England in September 1700. As the result of his researches, he published a general chart, showing at one view the variation of the compass in all those seas where the English navigators were acquainted; and thus laid the foundation of that department of science which has since received the attention of the greatest philosophers. His next employment, under the patronage of the king, was to observe the tides in the English Channel, with the latitudes and longitudes of the principal headlands; observations which were shortly after published in a large map of the Channel. In 1703, he was engaged by the emperor of Germany to survey the coast of Dalmatia; and returning in November of that year to England, he was elected Savilian professor of geometry on the death of Dr Wallis, and was also honoured with the diploma of LL.D.; a title somewhat more in consonance with his pursuits than that of "Captain," by which he had been styled from the time of his appointment to the command of the surveying vessel furnished him by King William. Dr Halley now gave his mind more entirely to mathematics, translating into Latin from the Arabic and Greek several treatises, which he afterwards published with supplementary matter, such as those of Appolonius and Serenus.

In 1719 he received the appointment of astronomer-royal at Greenwich, where he afterwards chiefly resided, devoting his time to completing the theory of the motion of the moon, which, notwithstanding his age, he pursued with enthusiastic ardour. In 1721 he began his observations, and for the space of eighteen years, scarcely ever missed taking a meridian view of the moon when the weather was favourable. He died at Greenwich in 1742, at the advanced age of eighty-six, having spent one of the most active and useful lives on record. His honours and titles

were numerous, but not more than his multifarious occupations and achievements entitled him to. In all, he exhibited the same promptness of resolve and incessant assiduity, willing to assist or be assisted; and never deigning it beneath him to confess when ignorant, nor to receive information from any quarter, however humble. Whether as Captain Halley, as secretary to the Royal Society, consulting engineer to the emperor of Germany, or astronomer-royal, he was the same ardent, prompt, and indefatigable labourer. His publications and papers were numerous; he gave important assistance to Dr D. Gregory in the preparation of the conic sections of Appolonius; and to Halley are we also indebted for the publication of several of the works of Sir Isaac Newton, who had a particular friendship for him, and to whom he frequently communicated his discoveries.

FERGUSON.

WE pass by several authors and observers who contributed, during the time of Huygens and Halley, to the advancement of astronomy, to notice the life of an individual whose career, while beneficial to the science under review, furnishes an ever-memorable instance of the acquirement of knowledge under the most pressing difficulties and obstructions. The most of those to whom we have adverted were men in independent circumstances, or at least so situated as to obtain at once a liberal education and the patronage and support of the great and wealthy. James Ferguson, the ingenious experimental philosopher, mechanist, and astronomer, to whom we allude, had no such advantages. He was born in 1710, a few miles from Keith, a village in Banffshire, in the north of Scotland. His parents were of the poorest order, but honest and religious, and, by toilsome labour in the cultivation of a few rented acres, contrived to rear to manhood a large family of children. Of the manner in which James acquired the rudiments of education, and how he struggled to rise from obscurity to distinction, we have a most interesting account in a memoir by himself, which we cannot do better than quote in an abridged form.

After mentioning how he learned to read with a very scanty aid from an old woman and his father, and that little more than three months' tuition at the grammar school of Keith was all the education he ever received, he thus proceeds:-"My taste for mechanics was soon developed; but as my father could not afford to maintain me while I was in pursuit only of these matters, and as I was rather too young and weak for hard labour, he put me out to a neighbour to keep sheep, which I continued to do for some years; and in that time I began to study the stars in the night. In the daytime I amused myself by making models of mills, spinning-wheels, and such other things as I happened to

see. I then went to serve a considerable farmer in the neighbourhood, whose name was James Glashan. I found him very kind and indulgent; but he soon observed, that in the evenings, when my work was over, I went into a field with a blanket about me, lay down on my back, and stretched a thread with small beads upon it, at arm's-length, between my eye and the stars, sliding the beads upon it till they hid such and such stars from my eye, in order to take their apparent distances from one another; and then, laying the thread down on a paper, I marked the stars thereon by the beads, according to their respective positions, having a candle by me. My master at first laughed at me; but when I explained my meaning to him, he encouraged me to go on; and, that I might make fair copies in the daytime of what I had done in the night, he often worked for me himself. I shall always have a respect for the memory of that man.

"I soon after was introduced by a schoolmaster whom I knew to a Mr Cantley, an ingenious man, who acted as butler to Thomas Grant, Esq. of Achoynaney, and from whom I received some instruction, particularly in decimal arithmetic, algebra, and the first elements of geometry. He also made me a present of 'Gordon's Geographical Grammar,' which at that time was to me a great treasure. There is no figure of a globe in it, although it contains a tolerable description of the globes, and their use. From this description I made a globe in three weeks at my father's, having turned the ball thereof out of a piece of wood, which ball I covered with paper, and delineated a map of the world upon it, made the meridian ring and horizon of wood, covered them with paper, and graduated them; and I was happy to find that by my globe, which was the first I ever saw, I could solve the problems. But this was not likely to afford me bread; and I could not think of staying with my father, who, I knew full well, could not maintain me in that way, as it could be of no service to him; and he had, without my assistance, hands sufficient for all his work."

Thinking it would be a very easy matter to attend a mill, and that he would have plenty of leisure for study, poor Ferguson next engaged himself to a miller; but the fellow turned out to be a harsh, ignorant drunkard, who required every moment of the boy's time, starving and ill-using him besides, so that at the end of a year he had to betake himself to the roof of his father. He next hired himself to a farmer; but here, again, he was worked beyond the strength of his naturally delicate constitution: illness ensued, and he had again to seek the paternal refuge. "In order to amuse myself in this low state, I made a wooden clock, the frame of which was also of wood; and it kept time pretty well. The bell on which the hammer struck the hours was the neck of a broken bottle. Having then no idea how any timekeeper could go but by a weight and a line, I wondered how a watch could go in all positions, and was sorry that

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