42 



VAPOR NUCLEI AND IONS. 



was observed at the fog chamber when isothermal conditions had been 

 reestablished. It should have been computed from the initial pressures 

 of both chambers and their common isothermal pressure when in com- 

 munication, in the way shown in the next section. The present results, 

 however, suffice for comparison with the preceding and following work, 

 and it is probable that limiting conditions of efficiency have already been 

 reached. That this is actually the case will also be shown in the next 

 section. 



40. Data for pipes 2 inches in diameter, 12 inches long. The results 

 obtained are fully given in table 15. It appears that coronas, even above 

 the large green-blue-purple type, appeared at the high exhaustions, but 

 this is not quite certain. 



Incidentally some data on the effect of X-rays from different distances 

 are included in the tables (part VI et seq.). The usual difficulty of an 

 inconstant X-ray bulb appears. Moreover, certain peculiar results on 

 the distribution of the nuclei within the fog chamber in case of symmet- 

 rical exposure to weak radium are here again noticed (part V), as in 

 Chapter I, section 4. The results are plotted in fig. 24 and smooth 

 curves obtained therefrom are shown in fig. 25. 



Table 15. Air nucleation at different supersaturations. Piping 2 inches in diameter, 

 12 inches long; plug gas cock, 2$ inches in bore. Wait 30 minutes between observa- 

 tions. Angular diameter of coronas, 2 sin -1 s/60. Eye 40 cm., lamp 250 cm., on 

 opposite sides of fog chamber, dp observed isothermally at the fog chamber. 



dp. 



s. 



Coro- 

 na. 



x 

 10- 3 



I. Non-energized dust- 

 free air. 



480 

 480 

 510 

 540 

 520 

 490 

 470 



410 



250 



91 

 250 



104 



,9-9 

 1.2 



120 



dp. 



Coro- 

 na. 



nX 

 10- 3 



I. Non-energized dust- 

 free air Cont'd. 



170 

 280 

 410 

 420 



470 



II. Air energized by X- 

 rays; D= 10 cm. 



470 

 480 

 510 



460 

 420 



390 

 380 

 230 



Coro- 

 na. 



nX 

 3 



10 



II. Air energized by X-rays; 

 D = 10 cm. Cont'd. 



170 

 230 



190 



19 



I 

 o 



Continued, next day; 

 D= 10 cm. 



o 

 o 



2 



87 

 180 



330 



1 Stone-blue colors, above gBP. 

 1 Irregular. Shows strong purple band just 

 above water. Coronas diffuse. 



'Stone- blue. 



4 Left over night seems to diminish rainlike 

 condensation. 



