316 Prof. Rutherford and Mr. Grier on Deviable 



The main object of the investigations described in this 

 paper was to obtain some experimental evidence of ihe 

 connexion, if any, between the deviable and non-deviable 

 rays emitted by the radioactive substances uranium, thorium, 

 and radium. It is known that cathode-rays striking on a 

 solid body give rise to Rontgen rays, and also that Rontgen 

 rays impinging on bodies in their turn give rise to a 

 secondary radiation, part of which is composed of rays 

 similar to cathode-rays. 



It thus appears possible, as Becquerel has suggested,, that 

 the non-deviable rays may be due directly to the action of 

 the deviable rays. A similar suggestion was put forward by 

 one of the authors * to account for the presence of the two 

 types of rays given out by uranium, one of which was far 

 more penetrating than the other. The relation is, however, 

 much more complicated than such simple analogies would 

 suggest. A discussion of the question, with especial reference 

 to the important results on the partial separation of the 

 active products of uranium and thorium, is reserved till the 

 conclusion of tbis paper. 



§ 2. In these experiments the electric method has been 

 employed throughout. It has many advantages over the 

 photographic method, especially where quantitative com- 

 parisons and rapidity of measurement are required. 



Fig. 1 shows the general experimental arrangement. The 

 radioactive substance to be investigated was spread uniformly 

 on the bottom of a shallow paper vessel, which fitted inside a 

 lead box 3 cms. square and 2 cms. deep. The paper vessel 

 rested on a wire gauze 1 cm. from bottom of vessel, and, by 

 means of a water-pump, a steady stream of air was drawn 

 downwards through the apparatus. This carried off the 

 radioactive emanation emitted by thorium and radium, the 

 presence of which in the testing-apparatus would seriously 

 interfere with the measurements. The lead box was placed 

 between pole-pieces, 3*2 cms. square, of a large electro- 

 magnet, which were generally placed 3*2 cms. apart. 



The testing-vessel V was a rectangular zinc vessel, 10*5 

 cms. square and 30 cms. high. The outside was connected 

 to one pole of a battery of 100 volts. A brass rod formed 

 the inside electrode, which was connected to the electrometer. 

 A guard-ring, connected to earth, ensured that there was no 

 natural leak from the charged cylinder to the inside electrode. 



The testing-vessel was placed on an insulated metal plate, 

 with a hole in the centre 3*2 cms. square, over the air-gap of 



* E. Rutherford, Phil. Mao-. Jan. 1899. 



