A CONTINUOUS RECORD OF 

 ATMOSPHERIC NUCLEATION. 



By Carl Barus, 



HAZARD PROFESSOR OF PHYSICS AT BROWN UNIVERSITY. 



CHAPTER I. 



THE RELATION OF IONIZATION TO NUCLEATION IN AIR AFTER CONTACT WITH 



PHOSPHORUS. 



1. Introductory. — The opinion was expressed in my earlier papers, that 

 wherever there is sufficiently intense ionization, there one may also expect to 

 find active nticleation; for it is hardly probable that a group of dissociated 

 molecules, neutral as a whole, can ultimately escape combination with each other 

 and the medium in which they are suspended. If these combinations occur in the 

 presence of water vapor, and particvilarly in a saturated atmosphere, the nuclei 

 due to solution may result. When the nuclei are produced from dilute solutions 

 by shaking, evaporation of the fog particle to the nuclear diameter might be 

 inferred; similarly, when the solute is produced by any kind of radiation or 

 emanation, each trace of soltite may grow in bulk by absorbing water to the 

 nuclear stage. In case of an intense emanation like that from phosphorus, this 

 process may actually continue until a visible cloud is prodticed and the nuclei 

 attain the size of fog particles. But it is to be borne in mind that the nucleus, 

 dissolved or not, is present initially, and is in case of phosphorus producible in 

 dry air ; whereas, in case of water nuclei produced by shaking or by jets, there 

 is no evidence of evaporation from the comminvited water particles, nor is it 

 certain that the nuclei here are mere water dust. One must keep in mind that 

 a nucleus may be the residue after the corpuscles representing the ionization 

 have been expelled. 



2. Method proposed. — If the original emanation, highly ionized though 

 neutral as a whole, is put through the process of condensation, then, if the 

 negative ions are more efficient as condensation nuclei than the positive ions, 

 the nuclei after condensation, or even after remaining in a saturated atmosphere, 



