A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



It is nevertheless interesting to note that the values of a obtained are of a 

 reasonable order of values even for the higher coronas, in which periodicity 

 supervenes. The corresponding graph (not shown) brings this out clearly. If 

 the values of a which correspond to normal coronas be selected, the following 

 summary is obtained: 



TABLE 6. VALUES OF a FROM APERTURE AND SUBSIDENCE. 



The mean of all the series is a = .00283; the mean of the fourth series, 

 which is more uniform, a =.00291. The latter datum will be taken in the 

 following computations. 



14. Summary of optic constants. The following series of values of a = ds 

 has been obtained when the measurements of aperture are made to the outer 

 edge of the first ring. 



Optically (blue), 

 From lycopodium 

 From subsidence, 



= .0032), 



-00344 

 .00336 

 .00291 



The latter datum is decidedly the smaller, corresponding closely to optical 

 puce-violet (.00293). If, in place of the above expression, the elementary 

 optical equation 2 sin<p = s/R = \/d or a = 30*. had been taken instead of a = 7 3 . 2 X , 

 even the extreme red would show but a" =.002 3. 



The datum for subsidence being simplest in character is apparently the 

 most trustworthy. Since = (6w/7ra 3 ) s 3 , if the method of Wilson and Thom- 

 son l be used for the computation of m the following values in grams per cubic 

 centimeter are applicable at the temperatures stated, for the pressure difference 

 dp=i'j cm. : 



0- 



m = 



10 



20 



3.7X10- 



4.6X10 



-6 



30" 

 5.7X10- 



Cf. J. J. Thomson, Phil. Mag. (5), XLVI, p. 538, 1898. 



