68 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



boundary of the fog, which at the outset appears as a sharp horizontal hne about 

 50 cm. long, even after i or 2 min. becomes more and more vague. Subsidence 

 is here accelerated. Hence it is chiefly for the normal coronas that subsidence 

 data are available, and, fortunately, it is precisely here that they are wanted. 

 In other cases the occurrence of periodicity and the rapid change of coronas 

 makes the interpretation tedious and difficult. 



The following table contains the results for subsidence. Stokes's well-known 

 formula reduces to R = gXio'^} v where R is the radius of the fog particle 

 sought. Temperature is denoted by 6 and current time by t, depth of the fog 

 line by x, and rate of subsidence by v. The diameter computed from aperture 

 is inserted for comparison. 2Rs = a is the new optical constant sought. The 

 braces denote the observations of x taken to compute v whenever the corona 

 changes character. 



It appears from the earlier parts of this table that although the coronas 

 may shrink and change appearance, this is not in the same measure the case 

 with the rate of subsidence. In the latter parts of a given series of observations, 

 therefore, the diameters from aperture are always in excess of those from sub- 

 sidence. With the growth of droplets, the two phenomena refer to different 

 particles, and hence only the original observations, i. e., those within the first 

 minute, are of any value. 



TABLE 5.— SUBSIDENCE OF FOG PARTICLES. PHOSPHORUS NUCLEI. 



COSITY OF AIR, ;? = . 00019. 



First Series. 



VIS- 



