i8 



A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



to those of the preceding chapter, and will lead to an examination of the infer- 

 ences already drawn for phosphorus nuclei. 



2. Apparatus. To detect the electrification of nuclei produced by shaking, 

 a 10 per cent, solution of sodic sulphate was employed, as this had been shown 

 to produce the nuclei in largest numbers under otherwise like conditions. 1 The 

 solution was used both to generate the nuclei by vigorously shaking the large 

 aspirator flask, A, figure i, containing a small amount of the solution at the 

 bottom, w, as well as to discharge the nuclei into the condenser, C, by filling A 

 with the liquid coming from the large Mariotte flask, M. Raising or lowering 

 the latter enabled the observer either to add liquid to A, or to withdraw it. 

 When a constant pressure was needed the device shown in the preceding chapter 

 (figure 2) was used, and the liquid passed along a side tube. The nucleated air 

 is discharged by the pipe, e s, into the tubular condenser, C, entering at 5. The 

 core of the condenser is highly charged and connected with one pair of quadrants 

 of the electrometer, E, the other pair being earthed and the needle kept charged 

 by a water battery, whose other pole is also earthed. The supports, i i, are of 

 hard rubber, those (g g) of the outer tube of the condenser are metallic, and 

 together with the base of the apparatus and the pipe, e s, are kept at zero 

 potential. 



The operations are evident. Having charged the core, the rate of discharge 

 is found when the current of nuclei traverses the condenser, the volume supplied 

 per second being read off on a scale attached to A. Results for nucleated air 

 (shaking) are alternated with results for dust -free air obtained by aid of the 

 filter and stopcock at F. 



3. Results. The results (two independent series) are given in the following 

 tables. The season was damp and unsuitable for electrostatic work, but the 



TABLE i. ELECTRIC CHARGES OF NUCLEI PRODUCED BY SHAKING A DILUTE 



SOLUTION OF Na a SO 4 . CHARGE IN CONDENSER, 40 VOLTS. 



o = d(log s)/dt; dV/dt IN LIT./MIN. 



TABLE 2. Same as preceding. 



' Structure of the Nucleus, p. 121. 



