PHILOSOPHICAL 
TRANSACTIONS. 
XII. A Description of a Transit Circle, for determining the 
Place of celestial Objects as they pass the Meridian. By the 
Rev. Francis Wollaston, LL. B. and F. R. & 
Read May 9, 1793. 
An instrument which, in one observation, is capable of giving 
with precision both the right ascension and declination of 
celestial objects, has always appeared to me one of the desi- 
derata in astronomy. Though I had often considered the va- 
rious methods practiced for ascertaining each, and turned it 
in my mind how I could contrive to make one instrument 
answer both purposes ; I never could satisfy myself in what 
way to effect the one. without destroying the accuracy of the 
other ; till one evening, at a meeting of our Society in the 
beginning of 1787, Mr. Ramsden mentioned to me his idea of 
reading off the divisions of an instrument, by a microscope 
having a micrometer in the field of view, which, being de- 
tached from the limb, could examine with accuracy the 
MDCCXC III. T 
