NUCLEATION IN LAPSE OF TIME. 



31 



28. Apparatus modified. The tubing of the preceding apparatus, 

 which consisted of inch plug cock and inch gas pipe, was now taken apart 

 and a i^-inch brass plug cock was substituted. The advantage of this 

 arrangement is easily seen, inasmuch as the whole resistance to flow is 

 practically in the pipes. The passage-way in the stopcock being larger 

 in area, the rate of exhaustion obtained is independent of slight differences 

 in opening. 



As a result of this, all the variations noted above practically disap- 

 peared, and the nucleations of dust-free air at a given pressure difference 

 were found to be constant in the lapse of time within the limits of 

 accuracy of the method. Data of this character are shown in the 

 following table : 



Table ii. Nucleation in the lapse of time. Sp = 30.6- cm. 



N X io _3 => 227. 



wog; n X 10 



3_. 



127; 



1 Apparatus with three sheets. 



s Apparatus with four sheets. 



3 Apparatus with one sheet, 10 cm. above surface of water. 



Indeed, the succession of different fog chambers with 1, 2, and 3 cloth 

 partitions all gave the same results. The rate of filtration could be 

 varied without effect within wide limits, and the same corona was 

 obtained after a few minutes or after 24 hours of waiting. 



29. Inferences. It has, therefore, not been possible to detect changes 

 of nucleation, either as the result of the concomitant changes of atmos- 

 pheric ionization or as the possible result of some form of cosmical or 

 at least external radiation. The consistency of the results obtained for 

 radiation under widely different conditions may be especially pointed 

 out. It does not follow, however, that other methods (not depending 

 on the terminal asymptote) may not be more efficient. In how far this 

 is the case will be shown in Chapter VI. 



