60 CONDENSATION OF VAPOR AS INDUCED BY NUCLEI AND IONS. 



To find, however, in how far the results themselves are trustworthy, 

 it will be necessary to find the computed values in the different series 

 of the diameter of the particles producing a given corona. For this 

 purpose the violet and green coronas are suitable. There are three of 

 the latter, the two upper being very brilliant. In the former report 

 the diameters of particles were estimated as d = 0.000460 cm. for the 

 middle green corona. Ratios of 4, 3, and 2 were usually apparent, 

 the data being multiples of a diameter something larger than d = o. oooi 5 , 

 the corona for which is not producible. In the present experiments 

 the values of d and 5 for the green coronas are given in table 2 1 . 



While there is considerable fluctuation, the data approach very closely 

 to a common mean, remembering that the color itself necessarily has 

 a certain latitude and wide differences of exhaustion are involved. 

 The ratio 2, 3, 4 of diameters of fog particles is not as well suggested 

 in the present result as in the former, while the absolute sizes themselves 

 are throughout smaller. It is nevertheless convenient to retain the 

 ratio for the division of coronas into successive series. If these may be 

 considered as beginning with deep red and ending with violet the fol- 

 lowing group may be postulated: 



TABLE 22. Showing cycles. 



v, (d =0.000 n cm.) v 2 , d = o. 00019 cm. i> 3 , d = 0.00033 cm. ^4> ^ = 0.00044 cm. 

 g, ( 13 cm.) g 2 , 23 cm. g 3 , 40 cm. g,, 52 cm. 



r, 16 cm. r 2l 32 cm. r s , 48 cm. r 4 , 64 cm. 



Only the red and crimson of the first series are certainly observable 

 with the above apparatus. Their aperture is about 60, their rings 

 diffuse, and their disk filmy, so that in a small apparatus they would 

 be mistaken for clear air. The second series is producible and vivid 

 throughout, and the same is even more true of the third. The fourth is 

 already closely packed, while the fifth and subsequent series merge into 

 each other too rapidly for separation. 



Series 3 and 4 were obtained in great number in my work with at- 

 mospheric nucleation. Selecting some twenty or more cases the mean 

 ratio i/5 3 : 1/54 = 0.146 : o.2o6=c? 3 : d 4 . Hence the ratio of 3 : 4 is 

 very well sustained. The goniometer distance from the fog chamber 

 was nearly a meter in this case. In the present experiments, however, 

 the short goniometer distance ( = 30 cm.), though adapted for the 

 best seeing, is not so suitable for measuring diameters. Apart from 

 this, the former experiments were made with plate-glass apparatus. 

 In cylindrical apparatus, as in the present case, there must have been 

 appreciable refraction due to differences of thickness. Hence it is 

 probable that the series i is actually the first occurring, although the 

 smallest active particles (violet) must exceed o.oooi cm. in diameter. 

 The same terminal conditions are suggested by the axial colors of the 



