V. Determination of the Latitude and Longitude of the 

 Observatory at Aberdeen : In Two Letters from 

 Andrew Mackat, L L. D. & F. R. S. Edin. to foHN 

 Plaifair, F. R. S. Edin. and Profejfor of Mathematics- 

 in the Univerfity of Edinburgh.. 



LETTER L 

 [Read 2d Dec. 1793.] 



Dear Sir, Aberdeen, i8th September 1793. 



SOME time ago I promlfed 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 power, I will reduce fome obfervations of occultations, 

 and of the late folar eclipfe, and fend yovi 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-lix primary divifions ; each of 



which 



