Barns — Nuclei produced by Shaking Different Liquids. 83 



Since the pressure ratio was in each case 1*36, the nuclei in 

 the influx air passing over burning sulphur or glowing punk 

 must have been 3*8 times more numerous. Thus there were 

 nearly 3 million sulphur nuclei and nearly 900,000 punk 

 nuclei per cubic centimeter in the laden air currents entering 

 the condensation chamber. 



I shall show elsewhere that the equation applicable to the 

 present experiments is 



(2 — Z) log y z ~ l 



n z =n z \0 n (1—S/s 2 ), 



z 



where n z is the initial nucleation, y the volume ratio on exhaus- 

 tion, z the number of the exhaustion and S an appropriate sub- 

 sidence constant. The function II is a product of the terms 



(i-s /s 2 z ) (i -s/sVO ■ • • (i-s/*%_,) 



so that Z is the number of the exhaustion in which the first 

 corona is seen and II = 1. When the particles are as large as 

 is the case for benzol the subsidence function is of prevailing 

 importance and masks the exponential function, as all the 

 observations for benzol show. I have carried this method out 

 for water vapor, obtaining consistent results throughout. The 

 present observations for benzol are scarcely systematic enough 

 to make, worth while to compute S, and the experiments should 

 be such in which the diffusion and homogeneity of vapor is 

 ensured by continued rotation of the vessel rather than by 

 shaking. But there can be no doubt that with proper pre- 

 cautions in this respect, # the number of nuclei furnished per 

 cubic centimeter by any given nucleator can be determined 

 with benzol vapor, as the coronas are all normal even for large 

 values of nucleation, with certainty. 



3. Axial colors.— -It is because of the relatively great num- 

 ber of relatively large particles in case of benzol and similar 

 hydrocarbon vapors, that the axial colors are seen and may be 

 traced into much higher orders than is the case with water 

 vapor. The yellows, browns, etc., of the first order may be 

 easily obtained with the steam jet though they can not be 

 produced in the condensation chamber by any means whatever. 

 The subsequent violets, blues, etc., however, are here distinctly 

 seen as far as the orange-red of the second order, after which 

 the admixture of white light makes recognition of color more 

 and more difficult. With hydrocarbon liquids like gasolene, 

 benzine, etc., the axial colors are seen much farther along the 

 series even through a short column, and they are intense in the 

 drum. The difficulty in observation encountered is due to the 

 slow diffusion and consequent absence of homogeneous vapor. 



