Jnd LONGITUDE of ABERDEEN. 137 



neareft feconat The next column contains the aggregate of the 

 three preceding columns, and is the fun's apparent central ze- 

 nith diflance. The eighth column contains the mean refradlion, 

 anfwering to the apparent zenith diflance of the fun's limb ; 

 hence the allowance for the contraction of the femidiameter at 

 low altitudes is avoided. The next column contains the mean 

 refradtion reduced to the true, by the application of the correc- 

 tions depending on the heights of the barometer and thermo-- 

 meter, as they are found in Table VIII. of my book on the 

 Longitude: In column tenth is the fun's parallax; and the quan- 

 tities in the two laft columns, appUed to thofe in column feventh, 

 give thefe in column eleventh, being the true zenith diflances 

 of the fun's centre. The following column contains the fun's 

 declination, reduced to the meridian of this place ; and in the 

 laft column is tlie latitude. 



Vol. IV. R Obferved 



