POND, JOHN. - TROUGHTON'S ASTRONOMICAL CIRCLE DESCRIBED.

On the Declinations of Some of the Principal Fixed Stars; With a Description of an Astronomical Circle, and Some Remarks on the Construction of Circular Instruments.

(London, W. Bulmer and Co., 1809). 4to. No wrappers as extracted from "Philosophical Transactions" 1809 - Part II. Pp. 420-454 and 1 large folded engraved plate depicting the large Circle Instrument (41x26 cm.).

The paper records observations made at Westbury and describes a simple method of correcting latitudes at places.
"The observations..were made..in the years 1800 and 1801 with an Astronomical Circle of twoo feet and a half in diameter, constructed by Mr. Troughton, and considered by him as one of the best divided instruments he had ever made; a drawing of it, with a short description, is annexed to the observations."

"Troughton made many contributions to the development of instrument making: in 1788 an improvement of Hadley's quadrant; in 1790 a mercurial pendulum; and in 1796 a refined version of the Borda, or reflecting circle. He was responsible for substituting spider web filaments for hair or wire in his optical instruments.....Troughton's most notable achievement was the improvement of the method of dividing a circle. His paper on this in 1809 won him the Copley Medal from the Royal Society, which elected him as fellow the following year."(DSB).

Order-nr.: 45171