190 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 30 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 JJL systematically reduced by 0.00124. Combining 

 this with the value found for A, the correction to Gylden's 

 constant becomes 



and a = 57". 548. 



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 ^=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 /A 



1. Fund. Astr 60". 320 1.00029257 



2. Tab Reg 440 29315 



3. Tab. Pulk 268 29232 



4. FuSS .122 29161 



5. Greenw. 1857-1865 .. .120 29160 



6. Pulk. 1865 .209 29203 



7. -Greenw. 1877-1886. . .192 2 9 I 95 



8. Pulk. 1885 058 29130 



9. Miinchen .104 29152 



