DETERMINATION OF ASTRONOMICAL REFRACTION. 



89 



From which we obtain 



d log r = -0 00132 ± 50 

 p = 515*7 



10. The Constant of Refraction. 



The value of a, the constant of refraction used by Bessel 

 in forming the table of refractions, Tabulce Regiomontance, 

 is a = 0*00027895 = 57"*538 



This is for barometer 29*6 inches, t = t' = 50° In the 

 tables used in this investigation, no information is given 

 with regard to any alteration of these values, so they are 

 here adopted. 



d log r = dr/r = -0*00132 

 therefore da = - 0*00132a 



= -0*"076 

 and a = 57-^62 



This reduced to the condition 760 mm. pressure at 0° and 

 temperature 0° O. gives 



a = 60 '283 

 u = 1-000292$ 



Appended will be found a list of the most important 

 determinations of the constant of refraction. These values 

 are for the conditions B equals 760 mm. at 0° O., the external 

 thermometer 0° O. 



u 



1. Tables Pulkowa .. 



2. Fuess 



3. Greenwich 1857-65 



4. Pulkowa 1865 



5. Greenwich 1877-86 



6. Pulkowa 1885 



7. Munich 



Mean values. 

 a = 60*"153 u = 1*0002918 



60*268 



1-0002923 



60*122 



2916 



60*120 



2916 



60*209 



2920 



60*192 



2920 



60*058 



2913 



60*104 



2915 



