2 A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



should become continually more positive, assuming that a greater number of 

 negative ions are removed by condensation. 



The investigation would therefore consist in testing the ionization imme- 

 diately coming from phosphqrus as to its power in dissipating positive and 

 negative charges, and in comparing these results with the degree of ionization 

 after the emanation has produced condensation. In other words, it is to be 

 ascertained whether the nuclei after a succession of condensations become con- 

 tinually more positive. 



The results to be discussed in the following paragraphs have made this ap- 

 parently straightforward investigation of little avail: for after the emanation 

 has reached the nuclear stage, scarcely 3 per cent, of the original ionization is 

 left. The residue is then so small that a decision of a possible excess of positive 

 or negative ionization is difficult, because the whole is now of the same order as 

 the normal leakage of the electrometer. 



In fact, the decision as to whether the positive or negative ionization is in 

 excess is now of very secondary interest, for the nuclei introduced into the 

 condensation chamber have already lost all but a trifle of their original charges. 

 The successive and even the initial condensations thus virtually proceed 

 without electrification. 



The initial intense ionization nearly vanishes even in a moderately dry 

 atmosphere. Indeed, it is hard to understand how a neutral, intensely ionized 

 emanation can be produced from a body like phosphorus. It appears to me 

 that the emanation is a molecular body which is stable in the presence of an 

 excess of phosphorus, i. e., at the surface, but which becomes unstable and 

 breaks to pieces in presence of an excess of air, on leaving the phosphorus. The 

 observed ionization is the accompaniment of this dissociation, and occurs on 

 the passage from the first environment to the second. If the ions were produced 

 by phosphorus directly, one would expect them to be either positive or nega- 

 tive, but not neutral. 



3. Water nuclei. After finishing the work with phosphorus, correlative 

 experiments with water nuclei were undertaken. It was found necessary, 

 however, to produce them in greater number than is possible by mere shaking, 

 to obtain marked effects. Hence jets were resorted to and studied in some 

 detail, as will be shown in succeeding chapters. The results obtained, though 

 closely resembling the phosphorus data in the main, differed from them inas- 

 much as the currents above a certain potential difference were constant, and 

 independent of the electromotive force of the condenser, while the ionization or 

 charge is not. neutral as a whole. Nucleation again remained equally effective 

 after the ionization had all but vanished in the speedy way observed for phos- 

 phorus. Here, too, however, it may be plausibly argued that the nucleus is the 

 stable product after the corpuscles representing the ionization have been 

 extruded. 



4. Comparison of the steam jet and the condensation chamber. A digression 

 may here be made relative to the indications of the colors of the steam jet and 



