THIS eminent mathematical and astronomical instrument-maker was the son of an innkeeper, at Salterhebble, near Halifax, in Yorkshire, and born there in 1735. He was educated first at Halifax free-school, and afterwards at an academy in Craven, Yorkshire, at which latter he made considerable proficiency in geometry and algebra, and took great delight in these studies. On leaving school, he was put apprentice to a clothier, at Halifax, for three years, at the expiration of which period, he entered the service of another manufacturer of the same town, in the capacity of clerk. This situation he exchanged, in his twentieth year, for a similar one in a London house; but, after he had stayed there two years, his inclination for mechanical pursuits so forcibly revived, that he quitted the clothiery line altogether, and bound himself apprentice to Mr. Burton, a celebrated thermometer and barometer maker, and engraver and divider of mathematical instruments. On the expiration of his apprenticeship, he hired himself, at the rate of twelve shillings a-week, as a journeyman workman, to one Cole, with whom he subsequently entered into a partnership, but soon effected a dissolution, and opened a workshop on his own account. He was not long in gaining employment from some of the most eminent mathematical instrument-makers of the day, and thus becoming intimate with Dollond, married his daughter about the year 1765. At this time he was not only master of the lathe and file, but of the art of grinding glasses, and had formed the design of examining every astronomical instrument in use, with a view of correcting those well designed, but imperfectly executed, and of proscribing those which were defective, both in principle and

construction.

Mr. Ramsden kept a shop in the Haymarket, from 1766 till 1774, when he removed to Piccadilly, and carried on business there for the remainder of his life. As early as the former year

he had invented his famous dividing machine, and brought the sextant to such perfection as never to give more than half a minute of uncertainty. The value of his labours, in this respect, to science, may be conceived from the fact that the same instrument generally in use among astronomers might fail by five minutes, and thus occasion, in the longitude, an error of fifty nautical degrees. The merit of his dividing

machine will be understood when it is stated, that a sextant can be divided with it in twenty minutes; and, in smaller works, it may be said to have superseded, in a great_measure, the use of beam compasses. For bringing this machine to perfection, the board of longitude gave Mr. Ramsden a premium of £1,000, and caused a description of it, with a plate, to be published, in 1777, which edition was, unfortunately, burnt, The theodolite was so far improved by Mr. Ramsden, as to serve, not only for taking angles, but also for measuring heights and distances. He made one for General Roy, of such accuracy, though only of eighteen inches radius, as not to admit an error of a single second. His alteration in barometers for measuring the height of mountains is another triumph of his skill. By marking at the bottom the line of the level, and looking at the top to the contact of the index with the summit of the mercury, he made it possible to distinguish the hundredth part of a line, and to measure heights within a foot. We may also here mention his superior execution of an electrical machine; a manometer, for measuring the density of the air; assaying balances, which turn with a ten-thousandth part of the weight used; the optic rectangle, prismatic eye-glasses, a dynameter, pyrometer, and a reflecting object-glass micrometer. Accounts of his successful improvement of the last instrument were published in the Transactions of the Royal Society for 1779 and 1785; and, in the following year, Mr. Ramsden was elected a mem

ber of that body, an honour his modesty had, for some time previously, led him to decline. In 1794, he was elected a member of the Imperial Academy of Sciences at Petersburgh; and, in 1795, he was presented with the annual gold medal of the Royal Society.

But the great works of the subject of our memoir are yet to be mentioned; these are the equatorial, the transit instrument, and the mural quadrant. A patent was granted him for the firstmentioned instrument, in which his chief improvements were, his rejection of the endless screw, which, by pressing on the centre, destroyed its precision; and his placing the centre of gravity on the centre of the base, causing all the movements to take place in every direction. Upon one of these instruments, the greatest that had ever been attempted, he was employed nine or ten years. It was made for Sir George Shuckburgh, and in so admirable a manner, that observations could be made nearly within a second. We have not space for a detail of the manner in which he improved the transit instrument; in this, as in others, exactness was his grand aim, and with that view one of his inventions was, a method for superseding the use of the spirit level. In the mural quadrant he has distinguished himself by the exactness of his divisions, and by the manner in which he has furnished the planes, by working them in a vertical position. A proof of the perfection to which he brought this instrument, is to be seen in one of six feet, which he made for the Duke of Marlborough, at Blenheim. "For this," says one of his biographers, "which is as beautiful as it is perfect, Mr. Ramsden invented a method of rectifying the are of ninety degrees, respecting which an able astronomer had started some difficulties; but with a horizontal thread, and with a thread and plummet, forming a kind of cross, which does not touch the quadrant, he showed him that there was not an error of a single second in ninety degrees; and that the difference arose from a mural quadrant of Bird, in which the arc of ninety degrees contained several seconds too much, and which had not been verified by so exact a method as this." It seems, however, that Mr. Ramsden preferred the whole circle to the quad

rant, and he is said to have demonstrated to M. de Lalande, that to attain to the utmost degree of precision of which observation is susceptible, the quadrant must be renounced entirely. The perfection to which he brought his instruments recommended him to such constant employment, that, although he kept sixty men, he was unable to execute all his orders; and persons who succeeded in purchasing, were considered fortunate. He sold them, however, at a cheaper rate than any other artist in the same line, in London, and was enabled to leave but a very small fortune behind him. His intense application to business at length injured his health, and having removed to Brighton, for the benefit of the sea air, he died there, on the 5th of November, 1800.

His character has been drawn in a very high strain of panegyric, by the Rev. L. Dutens, at the close of a memoir of him in Aikin's Biography. He appears to have been above the middle size, with a countenance full of sweetness and intelligence, frank and cheerful in manners, and full of humour, even to playfulness, among his intimate friends. His chief failing appears to have been a facility of temper, which induced him to break his promises to absent, in favour of present, friends; a graver defect in character than his eulogists or biographers seem to have considered. His temperance, simplicity of dress, and frugality, might have pointed him out as a miser, but for the total heedlessness of expense with which he pursued any new idea for the improvement of his instruments, and his utter indifference to all views of pecuniary profit. His whole life was devoted to his business, and it was less in the hours of relaxation than of illness, that he found time to make himself completely master of the French language. His manual dexterity was on a par with his scientific knowledge; and it is said that he could, with his own hands, have begun and finished every single part of his most complicated instruments. Of his skill in astronomical mechanism the preceding memoir will have furnished sufficient proof, nor need we, perhaps, add, that as an optician he was perfect; yet, to use the words of the writer above-mentioned, "While

Europe, in every corner, repeated his name with respect, it was, to a great portion of his countrymen, scarcely known, but as that of a very idle spectacle-maker; and he thus worked for every foreign nation with a marked predilection over his own countrymen." When he occasionally sent for a workman to give him directions concerning what he wished to have done, he first shewed the recently finished plan, then explained the different parts of it, and generally concluded by saying, "Now see, man, let us try to find

fault with it;" and if any improvement appeared to be feasible, he spared no expense to effect it. It is said to have been the custom of Ramsden to retire, in the evening, to what he considered the most comfortable corner in the house, the kitchen fire-side, and there, with his drawing implements, on the table before him, a cat sitting on one side, and a certain portion of bread, butter, and a small mug of porter placed on the other, draw some plan for torming a new instrument, or for the improvement of one already made.

THIS distinguished naturalist was born in the province of Nordland, in Sweden, where his father was minister, on the 28th of February, 1736. He received both his scholastic and medical education at Upsal, at the university of which place, he appears also to have taken his doctor's degree. After having made a tour to Russia, he was advised, by Linnæus, whose pupil he had been, to visit England; and he, accordingly, set out for that country in 1760. On his way thither, he happened to go on board a ship of war, for the purpose of seeing a friend who formed part of the crew, when the vessel was suddenly ordered to sail to the Canary isles; a circumstance which protracted the period of his arrival in England in a manner he had little anticipated. On reaching the metropolis, he presented a letter of introduction, from Linnæus, to Mr. Peter Collinson; which gentleman, in 1762, recommended him to the trustees of the British Museum, as a person, who had made natural history the study of his life, and was particularly qualified to draw up a catalogue of that part of their collection. In 1764, he was elected a fellow of the Royal Society; and, in 1765, one of the assistants to the British Museum, in the department of natural history. In the following year, he drew up, for Mr. Brander, the scientific description of his Hampshire fossils, entitled Fossilia Hantoniensia, &c.

In 1768, Mr. (afterwards Sir Joseph) Banks proposed to Dr. Solander to accompany him and the celebrated Captain Cook, in a voyage round the world, in pursuit of discoveries in his favourite science; and permission being granted him, by the trustees of the British Museum, to retain his appointment during his absence, he prepared to depart. Such a companion." it is observed, in the introduction to Captain Cook's first voyage," Mr. Banks considered an acquisition of no small importance; and, to his great satisfaction, the event abundantly proved that he was not mistaken." In the course of this voyage, he encountered many dangers in his ardour for botanical discoveries, and, in particular, during his ascent of a mountain in Terra del Fuego, in search of Alpine plants; on which occasion, Mr. Banks and himself were near losing their lives. According to the Dictionnaire Historique, the subject of our memoir had a salary of £400 a-year during his absence, but on what account is not stated: he had no public appointment, and was probably indebted to the munificence of Mr. Banks for his pecuniary resources at this time. In 1773, he was appointed one of the under-librarians in the British Museum, and continued to hold this situation till his death, which was brought on by apoplexy, on the 16th of May, 1782.

In testifying to the merits of Dr. Solander as a naturalist, Dr.

vessel containing the water, exposed to the fire. He ascertained also the quantity of coals necessary for the evaporation of any given quantity of water, the heat at which it boils under various pressures, and many other particulars never before accurately determined.

He now proceeded to attempt a remedy of the two grand defects of Newcomen's engine-the necessity of cooling the cylinder before every stroke of the piston, by the water injected into it; and the non-employment of the machine, for a moving power, of the expansive force of the steain. On account of the first defect, a much more powerful application of heat, than would otherwise have been requisite, was demanded for the purpose of again heating the cylinder, when it was to be refilled with steam. To keep this vessel, therefore, permanently hot, was the grand desideratum; and Watt at length hit upon an expedient equally simple and successful. His plan was to establish a communication, by an open pipe, between the cylinder and another vessel, the consequence of which would be, that when the steam was admitted into the former, it would flow into the latter, so as to fill that also. Supposing, then, that the steam should here only be condensed, by being brought into contact with cold water, or any other convenient means, a vacuum would be produced, into which, as a vent, more steam would immediately rush from the cylinder; this steam would also be condensed; and so the process would go on, till all the steam had left the cylinder, and a perfect vacuum had been effected in that vessel, without so much as a drop of cold water having touched or entered it. The separate vessel alone, or the condenser, would be cooled by the water used to condense the steam; which, instead of being an evil, would tend to quicken and promote the condensation. Experiments fully confirmed Watt in these views; and the consequence was, not only a saving of three-fourths of the fuel formerly required to feed the engine, but a considerable increase of its power. In overcoming this difficulty, Watt was conducted to another improvement, which effected the complete removal of what we have described as the

second radical imperfection of Newcomen's engine, namely, its non-employment, for a moving power, of the expansive force of the steam. The effectual way, it occurred to him, of preventing any air from escaping into the parts of the cylinder below the piston, would be to dispense with the use of that element above the piston, and to substitute there likewise the same contrivance as below, of alternate steam and a vacuum. This was to be accomplished by merely opening communications from the upper part of the cylinder to the boiler, on the one hand, and the condenser on the other; and forming it, at the same time, into an air-tight chamber, by means of a cover, with only a hole in it to admit the rod or shank of the piston, which might, besides, without impeding its freedom of action, be padded with hemp, the more completely to exclude the air. It was so contrived, accordingly, by a proper arrangement of the cocks, and the machinery connected with them, that while there was a vacuum in one end of the cylinder, there should be an admission of steam into the other; and the steam so admitted now served, not only by its susceptibility of sudden condensation, to create the vacuum, but also, by its expansive force, to impel the piston."

These were the principal fundamental improvements in an engine, which has since been brought to such perfection of action and power, as to form one of the most triumphant eras in the history of human ingenuity. Instead of entering into all the subsequent contrivances which Watt invented, we cannot give a better idea of his splendid success, than by quoting the language of a recent writer. "In the present state of the engine, it appears a thing almost endowed with intelligence. It regulates, with perfect accuracy and uniformity, the number of its strokes in a given time, counting or recording them, moreover, to tell how much work it has done, as a clock records the beats of its pendulum; it regulates the quantity of steam admitted to work; the briskness of the fire, the supply of water to the boiler; the supply of coals to the fire; it opens and shuts its valves with absolute precision as to time and manner; it oils its joints; it takes out any