V. Determination o//^(? Latitude and Longitude of the 

 Observatory at Aberdeen : In Two Letters from 

 Jndrew Mack at, L L. D. & F. R. S. Ed in. to John 

 P LA r FAIR, F. R. S. Ed IN. and Profeffhr of Mathematics- 

 in the Univerfity of Edinburgh ». 



LETTER L 

 \^Read 2d Dec. 1793.] 



Dear Sir, Aberdeen, iSth September 1793. 



OME time ago I promifed to fend you the refult of a feries 

 of obfervations, made to determine the fituation of this 

 place. Having, however, been much hurried of late, I am only 

 able at prefent to tranfmit you the determination of the latitude, 

 deduced from a feries of obfervations of the fun's meridian ze- 

 nith diftances. With refpedl to the longitude, as foon as it is 

 in my pow^er, I will reduce fome obfervations of occultations, 

 and of the late folar eclipfe, and fend you the refults. 



The following obfervations of the fun's meridian zenith di- 

 ftances were made with a moveable quadrant of two feet radius, 

 conftrudled by Mr Macculloch of London. This qua- 

 drant has two feparate fets of divifions : the quadrantal arc of 

 the inner fet is divided into ninety degrees as ufual ; and the 

 exterior arc is divided into ninety-fix primary divifions ; each of 



which 



