92 



NUCLEATION OF THE UNCONTAMINATED ATMOSPHERE. 



Iii the following table the weather is given in terms of F fair, Fc 

 partly cloudy, C cloudy, R rain, Sn snow, S sun ; the wind directions, 

 in points of the compass. The coronal angular diameter, <, is such 

 that 30 X 2 sin </2 = s, or nearly < = 5/30, when the eye at the goniom- 

 eter and the source of light were at distances 85 cm. and 250 cm., 

 respectively, from the fog chamber between them. N is not corrected 

 for the temperature (C.) of the apparatus, this being added in the next 

 table. The reduction from s to N is made as in Barus's memoir 

 (Smithsonian Contributions, 1905, Vol. xxxiv), and the measurement 

 of s made to the outer edge of the red ring, coinciding with the inner 

 edge of the blue or green rings. Exhaustions were made to a pressure 

 difference of 8p = 17 cm. 



TABLE 57. Successive observations of the nucleation (vVin thousands per cubic cen- 

 timeter) of the atmosphere at Block Island. 



