Born October, 1753. Died June 12, 1835.

Edward Troughton, the first astronomical instrument maker of our day, was born in the parish of Corney, on the south-west coast of Cumberland, and was the third son of a small farmer. An uncle of the same name, and his eldest brother John were settled in London as mathematical instrument makers; and as his second brother was apprenticed to the same business, Edward was designed to be a farmer, continuing to be his father's assistant till the age of seventeen.

The death of his younger brother, however, altered Edward's destination, and caused him to be placed with his brother John, at that time a chamber master, employed chiefly in dividing and engraving for the trade, and the higher branches of the art. Under the instruction of John, who was an excellent workman, Troughton made very rapid progress, and at the end of his time was taken into partnership.

About the year 1782 the Troughtons established themselves in Fleet Street, where they commenced an independent business and soon rose into eminence. After the death of his brother John, Edward alone continued the business until the year 1826, when increasing age and dislike to routine employment, induced him to take Mr. William Simms as his partner and successor.

The instruments which facilitate navigation were peculiarly objects of interest to Mr. Troughton, and long after his infirmities were an effectual bar to the applications of his most esteemed friends, he exerted himself to supply the seamen with well adjusted and accurate sextants. "Your fancies," he would say, "may wait; their necessities cannot."

In 1778 he took out a patent for the double framed sextant, a construction which, combining firmness and lightness, yet admitted of a considerable radius in this invaluable instrument. After trying and rejecting the repeating reflecting circle of Borda, Mr. Troughton, in 1796, hit upon one of his happiest constructions, the British reflecting circle, as he delighted to call it, an instrument which in right hands is capable of wonderful accuracy. It is a characteristic trait of Mr. Troughton, that in order to bring his favourite circle into general use, he reduced its price far below the usual profits of trade; and if he had succeeded in his attempt, he might have been ruined by his success, for his sextants were by far the most gainful article of his business.

With the same earnestness to promote the interests of navigation, he invented the dip sector (afterwards re-invented by Dr. Wollaston), and expended time, money, and ingenuity to no inconsiderable amount, in attempting to perfect the marine top for producing a true horizontal reflecting surface at sea. The marine barometer, the snuff-box sextant, and the portable universal dial, owe to him all their elegance, and much of their accuracy. Where others invented or sketched he perfected.

In the ordinary physical apparatus Troughton made considerable improvement in the construction of the balance, and of the mountain barometer. In the same class may be mentioned the form given to the compensated mercurial pendulum; his pyrometer, by which some very valuable expansions have been determined; the apparatus by which Sir George Shuckburgh attempted to ascertain the standard of weight and measure; and that apparatus which, in the hands of Francis Baily, has given an invariable simple seconds pendulum. In the ordinary geodesical instruments Mr. Troughton greatly improved the surveying level and staff, and reduced them both in weight and price, with increased convenience and accuracy. It is, however, in the construction of astronomical instruments that this great mechanician particularly excelled; here he reigned without a rival. His portable astronomical quadrants are models of strength and lightness, while the repeating circle of Borda, an instrument which he disliked, first received its beauty and accuracy from his hands.

The ordinary reading micrometer, and the position micrometer, commonly employed in the measurement of double stars, were greatly improved by him in simplicity and brought to perfection; and he first applied the former to dividing, though in circles and scales it had already been used in reading off.

Mr. Troughton's larger works, such as his equatorial instruments, circles, transits, &c., are as well known in the astronomical world as those of Wren in the architectural; they are too numerous to mention here, and are distributed in various parts of the world. The gigantic zenith tube at Greenwich was about the last work on which he was engaged, and he had just time to finish it before his strength failed. The only astronomical instrument which is not greatly indebted to Mr. Troughton is the telescope, and he was deterred from making any attempt in this branch of his art by the curious physical defect of colour blindness, which existed in many members of his family. Like Dalton he could not distinguish colours, and had little idea of them, except generally as they conveyed the impression of greater or less light. The ripe cherry and its leaf were to him of one hue, only to be distinguished by their form. With this defect in his vision he never attempted any experiments in which colour was concerned; and it is difficult to see how he could have done so with success.

The most remarkable of Troughton's writings are, 'An account of a method of dividing astronomical and other instruments by ocular inspection,' &c.—Phil. Trans., 1809, which was awarded with the Copley medal; 'A comparison of the repeating circle of Borda, with the altitude and Azimuth Circle'—Memoirs R. Ast. Soc.; and several articles in Brewster's 'Edinburgh CyclopÆdia,' such as 'Circle,' 'Graduations,' &c.

In the year 1825 Mr. Troughton paid a visit to Paris, and in 1830 he received an honorary gold medal from the King of Denmark. During the latter portion of his life he became almost entirely deaf, only hearing by the aid of a powerful trumpet. He died at his house in Fleet Street, June 12, 1835, in the eighty-second year of his age, and was buried at the Cemetery, Kensal Green.—Monthly Notices of the Royal Astronomical Society, vol. 3, February, 1836.