CHAPTER VI. 



SUMMARY AND CONCLUSIONS. 



89. Introductory. Researches have been made both with respect to 

 the ordinary relatively large or dust-like nuclei contained, i. <?., such 

 as will not pass through the cotton filter, and with respect to the 

 nuclei much smaller in size and probably belonging to the molecular 

 system of air, as they are inseparable from it by filtration. Nuclei of 

 the former class are usually (though not necessarily) foreign in char- 

 acter. Those of the latter class may also be so ; but as they are 

 demonstrably small, even when compared with the ions, and are 

 speedily reestablished if withdrawn from the air, their true nature may 

 be that of colloidal air molecules. Being present in thousands and 

 millions per cubic centimeter, in proportion as the order of molecular 

 size is approached, they are not to be identified with the ions for this 

 reason alone, as the number of the latter is insignificant in compari- 

 son. From what has been stated, colloidal air molecules (nuclei) can 

 not be regarded as stable chemical bodies, since, if precipitated by 

 condensation, they are immediately reproduced in the medium of moist 

 air out of which the precipitation took place. They can not be brought 

 to vanish in long periods of decay. In fact, the coronas of filtered air 

 attain their maximum size after long waiting; for in this way all other 

 larger nuclei which may incidentally be present are brought to vanish. 



Hence one must conclude that the nuclei which pass the filter are 

 present in a definite ratio dependent on the conditions of chemical 

 equilibrium of the most general kind.* As a rule, for each such 

 nucleus which decays, another is generated in the nonenergized dust- 

 free air in question, leaving the nuclear status constant. 



If we, furthermore, suppose that the formation of a nucleus is accom- 

 panied by the expulsion or the absorption of a corpuscle representing 

 the ionization, it is clear that a very high degree of nucleation may 

 be compatible with a very low order of ionization, such as is the case 

 with ordinary dust-free air ; for the concomitant ionization represents 

 the degree to which a decaying nucleus is not at once replaced by a 

 newly generated nucleus of the same type, and vice versa. In other 

 words, the ionization present represents the oscillation of the system 



* Including the effect of internal and possibly external radiations. 

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