530 Mr. W. Makower on the Method of Transmission 



Table III. (Vessel III.) diameter 8*3 cm. 



Pressure Activity 



in cm. mercury. on rod. 



5-3 394 



5-15 410 



4-15 413 



2-0 409 



1-7 398 



1-4 385 



1-05 386 



0-8 367 



0-41 332 



0-38 346 



0-17 268 



0-10 178 



0-086 170 



4, Discussion of Results. 



The experiments described above show that, at low pres- 

 sures, the excited activity produced from radium emanation 

 contained in a closed vessel is not confined to the cathode, as 

 in the case at high pressures, but is distributed over the walls 

 of the containing vessels and appears both on the anode and 

 cathode, even in a strong electric field. This is precisely 

 what has been previously found with thorium emanation *, 

 and shows that the method of transmission is probably the 

 same. 



It will be further noticed from the results given above 

 that in a large vessel the influence of pressure on the con- 

 centration of the excited activity on the cathode becomes 

 appreciable only at low pressures, whereas with smaller 

 vessels this influence is noticeable at much higher pressures. 

 If, therefore, we assume that at the moment of its production 

 the excited activity is uncharged, it is evident that the pro- 

 portion of particles of excited activity which can traverse 

 the gas in which it is formed, and reach the anode without 

 becoming charged, is a function of the length of its path 

 through the gas. As has been pointed out by Rutherford f , 

 there are two ways in which the excited activity may be 

 supposed to acquire a positive charge. 



(1) The excited activity condenses on the positive ions 

 existing in the gas and is thus transferred to the cathode; and 



(2) The excited activity possesses the property of expelling 



* Rutherford, loc. cit. 



t Rutherford, Phil. Mag. [6] vol. v. p. Ill (1903). 



