62 



BULLETIN OF THE UNIVERSITY OF WISCONSIN 



From the Pulkowa Tables we find: 



o o 



= 751.5 mm. r =9.31C. -* = 271.05 C. 



Denoting the quantity enclosed in brackets by F and ii 

 troducing numerical values, we obtain: 



BF 



It = [l.33207] 



tan z 



271,05 + r 

 log F = - (46.2 + 0.22 r) tan*z 



In the use of these formulae B and T must be expresse 

 in millimeters and degrees C. The formula gives log F i 

 units of the fifth decimal place. The number enclosed i 

 brackets is a logarithm. 



The corresponding formulae, when the pressures are e: 

 pressed in English inches and the temperatures in degree 

 F., are: 



R = [2.992151 AKK n F . tan z 



L J 455.9 + r g 



log F (42.3 + 0.12 r) tan*z 



The computation by these formulae is not more laborioi 

 than the direct computation from the tables, and the fo 

 lowing comparison shows that the differences between tl 

 formulae and the tables are far less than the uncertainty i 

 the tabular numbers themselves. For zenith distances nc 

 much exceeding 75 the formulae may be considered fc 

 most purposes a complete equivalent for the tables : 



COMPARISON OF THE REFRACTIONS FURNISHED BY THE 

 FORMULAE AND BY THE PULKOWA TABLES. 



