176 



C. Bar-us — Distribution of Nuclei. 



insure complete saturation of air. O is a stopcock leading to 

 an efficient filter (not shown). Supersaturation is produced 

 by sudden exhaustion at the B-end of the apparatus, while 

 the A -end receives the radiation from the X-ray bulb B '. A 

 large vacuum chamber was placed in connection with the 

 exhaust pipe shown, through a wide stopcock, the details of 

 which need not be explained. The X-rays used were not very 

 penetrating, and were obtained from a soft bulb actuated by a 

 small induction coil (4" spark) and 3-5 storage cells. Two 

 filters of solidly packed cotton were used, one 7 inches and the 

 other 16 inches long. They were about equally efficient. 



3. Vertical radiation at one end of the trough, entering 

 through wood. — In the preliminary experiments the bulb was 

 placed so as to radiate into the trough in the position shown 

 at i?, and kept in action 5 min. The effect was then observed 

 by condensation at the pressure difference hp = 17 cm . Two 

 results were noted : in the first place while the coronas 

 obtained with the X-rays in bulky apparatus are usually of the 

 smaller or normal type, the coronas seen in this shallow appa- 

 ratus were often enormous, transcending the middle g-b-p 

 corona (nucleation, n = 100,000 per cub. cm.). Even after two 

 or three subsequent exhaustions, filtered air being added prior 

 to each, large coronas were still in evidence. 



In the second place, the coronas, and hence the nuclei, were 

 observed chiefly on the A-side of the apparatus, under the 

 bulb. Fearing that there might be some direct effect due to 

 induced high potentials, the X-ray bulb was raised 10 and 20 cm 

 above the trough, with results naturally smaller in magnitude 

 but of the same kind. The following data may be given: 



Table 1. — Number of nuclei, n, in thousands per cm 3 . 6p = 17 c 

 angular aperture <p=s/S0. 



Temp, about 20 c 





adiation _ 





Bulb near trough (2 cm ) 



Bulb 10 cm 

 above trough 



Bulb 20 cm 

 above trough 



Tiinp of i 



5 min. 



5min. 



5 min. 



6 min. 



5 min. 



6 min. 













s 



n 



s 



n 



s 



n 



s 



n 



s 



n 



s 



n 



Coronas 



on 1st ex 



haustion 



* 



— 



* 



— 



* 



— 



3-9 



20-5 



3*5 



15 



2-7 



6'6 



a 



" 2d 



a 



5-9 



6-8 



— 



— 



6-5 



100 



2-7 



6'6 



2-7 



6-6 



1-9 



2-2 



a 



" 3d 



u 



— 



— 



— 



— 



5*9 



68 



— 



— 



— 



— 



— 



— 



* Immense but too diffuse for measurement. 



In all cases the first coronas were accompanied by dense rain 

 and fogs frequently in horizontal strata, so that sharp meas- 

 urements of aperture are generally out of the question. More- 

 over the first condensation is accompanied by turbulent dis- 

 placement of fog-particles, and the contents of the receiver 

 are thoroughly stirred up. After filling with filtered air and 



