C. Barus — Note on the Constants of Coronas. 325 



Art. XXXII. — Note on the Constants of Coronas; by 



C. Bakus. 



1. In the course of my work with atmospheric nucleation, it 

 appeared that the standardization of coronas which I published 

 some time ago^ is inadequate for the purpose. A revision has 

 become necessary of such a kind as to inchide the features 

 which have developed in the intervening time, in particular 

 the occurrence of marked periodicity in the nucleation [n 

 particles per cubic centim.) as related to aperture, and of the 

 exhaustion losses of which there was no indication in my 

 earlier work. The origin of the latter was for a long time puz- 

 zling, but they are now completely referable to the subsidence 

 of fog during the brief period within which the coronas are 

 visible and the nuclei loaded by condensation. I will show else- 

 where that if successive identical partial exhaustions of the vol- 

 ume ratio y are presupposed, the phenomena are expressed by 



n, = n^ 1 0^^-^^ '°g ^ n ( 1 - /S/s^) 

 z 



where Z is the number of the fiducial and z of any subsequent 

 exhaustion, Ur^^ and n^^ the corresponding nucleations, S the 

 appropriate subsidence constant and s the current relative 

 aperture of the corona. 11 is the function (1 — /6yc^|)(l — /cS'/^l+i) 

 '..... (1— '6'/<§|_i). The constant S ma^^ either be computed 

 from observation of s and n in the region of normal coronas 

 (where n=Cs^ is known) or it may be computed from the 

 observed time of fog suspension. Clearly all observations 

 must be made strictly in time series. 



To be independent of the optics of coronas which are not 

 worked out, I have determined the diameter of fog particles 

 from subsidence experiments. Thus for an observed aperture, 

 ^0, the diameter cZ„, from subsidence gives the fundamental 

 constant, s^d^ = a". This constant differs materially from 

 a' = ds di's> found from diffraction measurements, as the tables 

 show. The corresponding n values in the former case are 

 about twice as large as the n values in the latter, seeing that 

 the cube of a enters the equations. 



2. Explanation of tables. — To correlate the present with 

 my eai'lier investigations I will give a series of results found 

 by using a small circular part of the Welsbach mantel as a 

 source of light. Coronas in this case are more easily identified 

 becaused of the simplified color scheme, to the practical advan- 

 tages of which I have already referred. These are followed 

 by results with electric light seen through ruby glass. 



* This Journal, xiii, p. 81, 1902; Phil. Mag. (6), iv, 1902, p. 24. 



