A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 19 



data are sufficient to indicate the extreme smallness of the effect to be observed. 

 Ohm's law being assun:ed as usual, as a rough approximation to the truth, the 

 readings in scale parts, s, are read off, at the successive times, t, of observation. 

 The constant then follows as a = d{log s)/dt and dV/dt denotes the number of 

 liters of air, nucleated or not as stated, put through the condenser. In table i 

 the leakage, a, is larger for negative than for positive charges, but the effect is 

 equally large no matter whether the influx is dust -free and filtered or whether 

 the nuclei produced by shaking traverse the condenser. Shaking is thus without 

 an electrical effect, so far as can here be discerned. What has been observed 

 in both cases is a continuous drift of the needle. 



In table 2, for another adjustment, the positive and negative charges leak 

 out equally fast when dust-free air constitutes the medium of the condenser. 

 When shaken nuclei circulate through it, the negative charge leaks out more 

 rapidly than the positive charge, implying positively charged nuclei. But as 

 the restilt is no larger than for dust-free air, it is again probable that the mere 

 drift of the needle is being observed. 



The results from both tables are therefore negative, showing that the excess 

 of leakage for a charge of one sign over that of another must be of the order of 

 .001 when referred to minutes, if the nuclei in question are produced by shaking. 

 This result, however, is not unexpected ; for it is not more than about a thousand 

 nuclei that are here available, and with the necessarily small charge residing on 

 each, a detection of the effect will not easily be accomplished in connection with 

 moist air. The following pages, moreover, will show how qtiickly the charge 

 vanishes, and I am not sure that the experiments were made expeditiously 

 enough. Hence I waived the experiments temporarily, to be resumed with a 

 more efficient method of producing water nuclei and during the dryer atmos- 

 pheric conditions of winter. 



THE EFFICIENCY OF NUCLEI-PRODUCING JETS. 



4. Powerful methods of comminution. — It appears from the preceding 

 section and elsewhere that the number of nuclei produced by shaking is rela- 

 tively very small, and the coronas correspondingly simple. To obtain more 

 nuclei a much more violent niethod of comminution must be resorted to, such as 

 is given if fine jets of water, generated under high pressure, are shattered either 

 against a solid obstacle or against each other. Fortunately, ordinary hydrant 

 water coiitains enough solute to answer the requirem-ents, and the construction 

 of the jet is thus a straightforward problem. It will be found that for each jet 

 there is a maximum of productivity, and one is thus able to make a series of 

 jets, each corresponding to a definite number of nuclei under like conditions. 

 Each jet has a definite saturation number, and while the maximum satttration 

 producible in this way is naturally far below the efficiency of phosphorus and 

 other chemical ionizers, so far as nuclei are concerned, the aggregate ionization 

 is not very different. 



