I. MEASUREMENT. 399 



1781. 12-inch Astronomical Quadrant, by Bird, em- 

 ployed in the observations of the transit of Venus. 



Royal Society,. 



1782. Prismatic Circle, constructed in 1843, from the design 

 of Professor Kaiser. 



H. G. Van de Sahde Bakhuyzen, Director of the Observa- 

 tory, Ley den. 



By means of two observations the measurement of the angle can be obtained 

 without any instrumental error, excepting those of division. Angles can be 

 measured from to 170. 



1783. Kaiser's Prismatic Circle, constructed on the same 

 principles as the preceding. The construction of the stand) 

 and of a few details, have been improved in this second model. 



H. G. Van de Sande Bakhuyzen, Director of the Observa- 

 tory, Leyden. 



d. EQUATORIALS. 



1784. Equatorial Telescope by Abraham Sharp. 



The Council of the Yorkshire Philosophical Society \ 



Abraham Sharp, eminent mathematician, mechanist, and astronomer, 

 descended from an ancient family at Little Horton, near Bradford in York- 

 shire, was born about 1651. He was apprenticed to a merchant at Manchester, 

 but his genius led him strongly to the study of mathematics, both theoretical 

 and practical. By the consent of his master, he quitted business and removed 

 to Liverpool, where he studied mathematics, astronomy, &c., and where for 

 a subsistence he opened a school, and taught writing and accounts. He had 

 not been long at Liverpool when he fell in with a merchant from London, in 

 whose house the astronomer, Flamsteed, then lodged. Sharp contracted an 

 intimate friendship with Flamsteed, by whose interest and recommendation 

 he obtained a more profitable employment in the dock} r ard at Chatham, 

 where he continued till his friend and patron, knowing his great merit in 

 astronomy and mechanics, called him to his assistance in contriving, adapt-* 

 in, and fitting up the astronomical apparatus in the Royal Observatory at 

 Greenwich, which had been recently built, about 1676. He was principally 

 employed in the construction of the mural arch, which in 14 months he 

 finished, greatly to the satisfaction of Flamsteed. According to Smeaton 

 this was the first good instrument of the kind, and Sharp the first artist 

 who cut accurate divisions upon astronomical instruments. When it was 

 constructed Flamsteed was 30, and Sharp 25 years of age. Sharp assisted 

 Flamsteed also in making a catalogue of nearly 3,000 fixed stars, with their 

 longitudes and magnitudes, their right ascensions and polar distances, with 

 the variations of the same while they change their longitude by one degree. 

 Among other indications of great genius, it was stated that Sharp made 

 most of the tools used by joiners, clockmakers, opticians, and mathematical 

 instrument makers. The telescopes he made use of were all of his own 

 making, and the lenses were ground, figured, and adjusted with his own 

 hands. He died July 18th, 1742, aged 91. 



