68 THE STRUCTURE OK THE NUCLEUS. 



The source of light and the goniometer were each distant 2 1/2 meters from the 

 receiver of cloud particles. The diameter of the earlier cloud particles was com- 

 puted from vV, and found to be 



(l„ = 263 X 10~* for punk nuclei, in the globe, 

 (Iq = 350 X 10"* for sulphur nuclei, in the globe, 

 d^ = 360 X 10"* for punk nuclei, in the drum. 

 These values depend merely on the number of nuclei originally put in, but they 

 were purposely made as large as practicable. 



The precipitation for adiabatic exi)ansion was computed from I'x = Sb — Cb IgS, 

 where 5 is the absolute temperature, r the latent and O the specific heat of the 

 liquid, .S' the constant entropy and x/(l — x) the I'atio of vapor and liquid in the 

 chilled mixture. For coronas in the globe, m =z 79 X 10" ^ grams of water were 

 precijiitated per cub. cm., and for axial colors in the drum, ?n = 36 X lO'** grams 

 of water weie precipitated. 



Finally, the absolute number was found from ni = ?i x ^ X ^* = « X ^ whence 

 for coronas in the globe, n = 8.3 X lO"* x jV, in case of punk nuclei, 



>i:= 3.6 X 10* X JV, in case of sulphur nuclei; 

 for axial colors in the drum, n =: 1.5 X KH x /V, 



with a weaker nucleatiim of punk nuclei. If A''= iV^ =: 1 or at the beginning of 

 the expeii mental series, 



n = 83,000, = 36,000, = 15,000, respectively, 

 depending on the number of nuclei arbitrarily introduced. 



The axial colors completely vanish befoi'e one half of the coronas have been 

 passed. Experiment shows, therefore, conformably witli the interpretation just 

 adduced and apart from discrepancies due to insufficiently uniform distributions, that 

 columns 5 to 13 meters long are necessary if saturated axial colors are to be observed. 



Axial colors may, therefore, be pi'oduced by light which has passed through 

 the particles and to the same agency the colored fields may be referred. It is easy 

 to obtain color in the undeviated ray' (here the coronal center or axial color) when 

 plates or films are dealt with, by superimposing an interference phenomenon on the 

 diffraction phenomenon. For the sake of having a convenient scale of distribution, 

 I mapped out the axial colors in this way in my earlier volumes. The case seems, 

 however, to be very different when droplets as small as 2/10* to 4/10* cm. are in 

 question. Here it is on the one hand difficult, in view of these small globules, to 

 interpret the entrance of light in such a way as to produce interferences. On the 

 other hand, the particles are too large to correspond to thicknesses which produce 

 the vividly colored Newtonian interferences of the first and second order, for in 

 such a case the plate must be of small thickness as compared with the wave length 

 of light. In the absence of an ade({uate theory or even an adequate suggestion, it 

 seems best, therefore, to leave the subject in abeyance, seeing that the light reflected 

 from the outside of the particles must at the same time be accounted for, as well 

 as the effect of the ap[)roach of the particles themselves. 



" References to the well-known experiments of Quincke and others, and an analysis of Row- 

 land's theory, will be found in Kayser's Handbuch d<r Spectroscopic, Leipzig, 1900, p. 428, et seq. 



