EXPERIMENTS WITH IONIZED AIR. 



31 



12. Discmsion. — To turn first to table 7, it is seen that whereas in the earlier 

 work the dust contents needed to produce a blue field was })ut .5 liter pei' minute 

 on the average, the requirements here are as liigh as 2 lit./min. and not below 1.2 

 lit./min. On the average even three times as much dust is needed. This is a dis- 

 advantage of the lu'esent form of jet, inasmuch as the law of absor[)tion in the tube 

 t, Fig. 9, has now a fundamental bearing on the data obtained from the apparatus, 

 which will in many cases outweigh the convenience of stronger colors of the second 

 order. The jet, moreover, is not available for the capture of atmospheric nuclei. 

 Different pui-poses will thei'efore be subserved by the two forms of jet. 



If these series of observations are examined individually as far as blue, they 

 will be found to lie on a line with somewhat less concavity upward than was the 



Fig. io. — Chart Obtained with New Jet Corresponding to Figures 3 and 4. 



case above. Their regularity, even for color eriteiia, is not as gi-eat as would be 

 anticipated, particulai'ly in the region of the second ordei' (right end of curve). As 

 the observations were taken on different days, it seems to me that the state of the 

 atmos[)here must impress itself upon these measurements, as the effect of atmos- 

 pheric nuclei would be largest on the right where the supi>ly of artificial nuclei is 

 smallest. 



Compared with the preceding results (figure 3), the present series of data lie 

 quite within the same margins of values. Indeed, the results with the jet dusted in 

 the great variety.of ways from without, the nuclei being borne into the jet on a 



