RAMSDEN, JESSE, will always occupy a distinguished position in the history of mechan • ism by his beautiful optical and astronomical instruments. He was born in 1735. At the age of 20 we find him engaged as a clerk in a cloth warehouse in London, in which capacity he continued till 1757-8, when his predilection for other pursuits led him to bind himself for four years to a working mathematical and philosophical instrument maker. He com menced working on his own account, and his skill as an engraver and divider gradually re commended him to the employ of the leading instrument-makers. Ramsden subsequently married Dollond's daughter, and he received with her part of Mr. Dollond's patent right in achromatic telescopes. His occupation afforded him frequent opportunities of observing the defective construction of the sextants then in use, the indications of which, as had been pointed out by Lalande, could not be relied on within five minutes of a degree, and might therefore leave a doubt in the determination of the longitude amounting to fifty nautical leagues. The improvements introduced by
Ramsden are said by Piazzi to have reduced the limits of error to thirty seconds. This circumstance, added to the cheapness of his instruments, which were sold for about two thirds the price charged by other makers, soon produced a demand which, even with the assistance of numerous hands, he found difficulty in supplying. In his workshops the principle of the division of labour was carried out to a considerable extent, and a propor tionate dexterity was acquired by the workmen; but it is asserted that in none of these, even the most subordinate, and least of all in the higher departments did the skill of the work men surpass that of Ramsden himself. His attention was incessantly directed to new provements and further simplification, the result of which was the invention of a dividing machine. From this time his fame was fully established as the first instrument-maker of his day. He died in 1800.