164 VAPOR NUCLEI AND IONS. 



limit) do not in their details, it is true, agree with the curves for appa- 

 ratus I, except to some degree on June 29 and 30. As a whole, how 

 ever, they also strikingly follow the march of the decrement of the 

 barometer. One may note, moreover, that it is not necessary that the 

 curves for apparatus I and II should quite agree. If, for instance, the 

 preponderating nuclei in the former case are colloidal, and in the latter 

 case ions, one should expect an inverse curve; for the ions in I would 

 decrease the number of efficient nuclei, whereas in II they would increase 

 their number. Decision must be deferred for further observation. 



In July the two fog chambers again fail to agree in their daily fluctua- 

 tions, but both nevertheless follow the barometer closely, in their broader 

 variations. The different sizes of coronas imply different ratios of ions 

 and colloidal nuclei, and hence detailed agreement should not be antici- 

 pated. On July 12 the fog chambers were subjected to modifications 

 and it was therefore concluded to terminate the preliminary series of 

 observations at that point, reserving further record and comment for a 

 subsequent report. 



103. Conclusion. It appears, therefore, at the present stage of progress 

 of the investigation on the time variation of the number of larger colloidal 

 nuclei in dust-free wet air, that the meaning of the above results is not 

 quite clear. The probable occurrence of an effect due to anything like 

 cosmical radiation may, however, be regarded as excluded. The nuclea- 

 tion curves vary in their broad contours with the barometer, being a 

 maximum when the atmospheric pressure is least. Nevertheless the two 

 fog chambers do not, in their detailed variation, show appreciable 

 accordance ; rather the reverse of this, and yet such a result may be due 

 to differences in the ratios of nuclei and ions entrapped in the differently 

 adjusted chambers. No. II in the above work (Chapter II, section 53) 

 shows apparent excess in the region of ions as compared with No. I. 

 As a whole the data for the time variation can not be regarded as quite 

 trustworthy, since the correction to be added for variation of baro- 

 metric pressure and the drop of pressure are in the same sense as the 

 residual effect observed. If some obscure factor in the make-up of these 

 corrections has been overlooked, the results may possibly be attributed 

 to it. 



From another point of view adequate explanation is now at hand, 

 why in the above investigations it was found impossible to secure rea- 

 sonably coincident results in the case of those groups of nuclei which 

 lie in the region of the larger colloidal nuclei and of the ions; and it is 

 chiefly for this reason that the results of this chapter are included in the 

 present report. 



