A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



71 



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 o = . 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 (d„ = 

 From subsidence. 



.0032), 



a =.003 44 

 .00336 

 .00291 



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

 puce-violet (.00293). If- i^ P^^'^^ °f ^^® above expression, the elementary 

 optical equation 2 smqj = s/R'=\/d or = 30! had been taken instead of a= 73.2A, 

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



The datum for subsidence being simplest in character is apparently the 

 most trustworthy. Since w= {bm/na') s\ if the method of Wilson and Thom- 

 son 1 be used for the computation of m the following values in grams per cubic 

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

 (J^=i7 cm.: 



= 

 m= 



10" 

 3.7X10- 



20 

 4.6X10" 



30" 

 5.7X10-" 



67. J. J. Thomson, rhil Mag. (5), xlvi, p. 538, 1898. 



