190 



CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



4. The Constant of Refraction. — The value of a deduced 

 by Gylden for the Pulkowa Tables, as given in his "Unter- 

 suchungen iiber die Constitution der Atmosphare u.s.w.," is 



a =0.00027985 = 57". 723. 

 This is for B = 29.5966 inches at o° and / = 7 . 44 R. 



The Pulkowa Tables used here, however, are Gylden's 

 with \x systematically reduced by — 0.00124. Combining 

 this with the value found for /\a, the correction to Gylden's 

 constant becomes 



/\a = — 0.00304a 



= - o".i75 

 and a = 57"-54 8 - 



This reduced to the condition of 760 mm. pressure at o° 

 and o° C temperature gives 



a= 60". 159. 



To this value of a correspond the following: 



c = 0.00029182 



and 



li = 1. 00029178. 



For the sake of comparison, the most important deter- 

 minations of the constant of refraction are given below. 

 These values are for the conditions B = 760 mm. at o° C 

 and external thermometer = o° C. (These values are taken 

 from Professor Bauschinger's "Untersuchungen iiber die 

 Astronomische Refraction u.s.w."). 



a 



Fund. Astr 60". 320 



Tab Reg -44° 



Tab. Pulk 268 



Fuss .122 



Greenw. 185 7-1 865. . .120 



Pulk. 1865 .209 



Greenw. 1877-1886. . .192 



Pulk. I885 058 



Miinchen . .104 



1.00029257 



2 93 x 5 

 29232 



29161 



29160 



29203 



29 x 95 

 29130 



29152 



