Electrical Conductivity of Atmospheric Air. 



707 



the pressures examined, that the conductivity was proportional 

 to the pressure. This result is what we should expect to obtain 



Fisr. 5. 



22 





















■\, 























■ 



/8 









































/ 



















I 





y 



/ 





















/ 



/ 





















/ 

















S 







/ 



T 























y 



/ 























4- 





/ 

























/ 









1 



















/ 







1 

















G 40 30 SZO /60 200 240 280 J20 360 40O fJO 480 



P/ressuffe //v Cms 



with an emanation maintained at a constant strength and 

 emitting a radiation of a penetrating nature. 



6. Penetrating Rays from External Sources. 



While the effects described up to the present may be 

 explained by supposing the ionization to be caused by a radio- 

 active emanation sent off from the metals, it has been found 

 that part of the conductivity cannot be accounted for in this 

 way, but must be attributed to an active agent external to the 

 receiver. 



The heavy cylinder referred to above was filled with air to 

 a pressure of about 400 cms. of mercury and allowed to stand 

 until its conductivity had become steady. It was then placed 

 in an insulated galvanized iron tank, 150 cms. in height and 

 75 cms. in diameter, which was gradually filled with water 

 so as to surround the cylinder with a layer 25 cms. in thick- 

 ness. The initial conductivity before the water was admitted 

 was 21*1. As the water rose the conductivity decreased and 

 fell to 13*3 when the tank had been filled. The values for 

 the conductivity during the experiment are given in Table IV., 

 and they show that the loss was almost directly proportional 

 to the rise of the water. The total fall in conductivity, it will 

 be seen, was about 37 per cent. 



