356 C. Barns — Large and Small Coronas. 



present a more striking contrast, since the third power of 

 aperture is involved. Otherwise but few new results are to 

 be inferred from them. If the long series of figure 1 be taken, 

 which contains the data of twenty successive alternations, the 

 average inferior nucleations are 11,800, and the average supe- 

 rior nucleations 94,000, supposing, of course, that the precipi- 

 tated water is the same in both cases and that it is all con- 

 densed on the available nuclei. In other words, if the two 

 cases are otherwise identical, the superior coronas correspond 

 to a number of nuclei eight times greater (frequently larger 

 than this in the other observations) than the inferior coronas. 

 As this explanation is the more probable, it follows that the 

 nuclei (as stated in §10) cannot be regarded as positive and 

 negative ions. They are rather the groups of large and small 

 nuclei seen throughout the condensations in connection with 

 the rain and the blurred coronas. Apart from this the num- 

 bers obtained throughout are quite out of keeping with any 

 similarly observed ionization. If, however, free electrons 

 appear only at the destruction or at the origin of nuclei, the 

 association of few ions with many nuclei . at any time subse- 

 quent to their origin, is well accounted for, as already sug- 

 gested in the earlier paper. It is only while the nuclei are 

 being produced that the ionization and the nucleation must be 

 of the same order; for the latter persists while the former 

 vanishes at once. Finally the following results are implied at 

 least for the physical structure of air saturated with water 

 vapor : 



Air (dust-free) is inseparably intermixed with large and 

 small nuclei, whose number (to be reckoned in millions per 

 cubic centim.) rapidly increases as the order of molecular size 

 is approached. There seems to be no objection to looking 

 upon these nuclei as a kind of colloidal (air) molecule, particu- 

 larly as such molecules are frequently producible by the means 

 (Bredig) which produce nuclei. If a large number of free 

 atoms is suddenly introduced into any region (and this is prob- 

 ably what the radiation of the above kind virtually does), the 

 result is not merely a production of typical molecules but of a 

 large concomitant of graded nuclei. 



Practically any given nuclear status of air is a counterpart of 

 the intensity of the ionization of the medium in which the 

 nucleation originated, to the effect that the superior limit of 

 size of the nuclei and their number increase with the ioniza- 

 tion. But there is no case of ionization free from nucleation, 

 be the exciting cause a mere radiation as above, or ignition, 

 combustion (including the low temperature cases like phos- 

 phorus), or high potential discharge, or violent comminution as 

 in the case of water nuclei, — the two manifestations being 

 often distinguishable by enormously different rates of decay. 



Brown University, Providence, R. I. 



