by Matter of the ft Particles emitted by Badiw 



173 



u> p" - "^ 



vessel was closed by a large ebonite stopper E, into which 

 fitted a brass cylinder F, of diameter 2 centims., as indi- 

 cated in the diagram, and the thickness of whose walls was 

 1*3 millim. ; the length of this tube was 11 centims. When 



in position, the tube A lay along the 

 axis of the brass tube F. The cylinder 

 F could be connected to a quadrant 

 electrometer by the wire W passing 

 through the ebonite stopper E. By 

 means of the platinum wire G, fused 

 through the stopper of the giass 

 vessel, the brass tube B, and there- 

 fore the aluminium-leaf covering the 

 tube containing the emanation, could 

 be maintained at any desired po- 

 tential by a battery of accumulators. 

 The platinum wire H, sealed through 

 the glass vessel, served to connect the 

 silvered surface of the glass to earth. 

 To carry out an experiment, the 

 silvered glass vessel was evacuated 

 as perfectly as possible by means of 

 charcoal and liquid air, and, by a 

 quadrant electrometer, the negative 

 charge reaching the brass cylinder F 

 from the tube containing the ema- 

 nation on account of the ft rays 

 emitted by it, measured. The walls 

 of the glass tubes containing the emanation, in the two 

 sets of experiments which were made, were *12 millim. 

 and *078 millim. thick respectively. This thickness of glass 

 was sufficient to completely stop the a rays coming from 

 the emanation, but insufficient to stop more than a small 

 fraction of the ft rays from radium C. The slowly moving 

 ft rays from radium B are nearly, though not completely, 

 absorbed by the above-mentioned thickness of glass. It 

 will thus be seen that the ft radiation reaching the brass 

 cylinder F consisted, for the most part, of the ft rays 

 from radium 0, together with a small amount of radiation 

 from radium B. In order to find the charge which would 

 be acquired by the cylinder on account of the radium C con- 

 alone, it is necessary to apply 



Co f ,.« 1 1 torn. 



idium reaching it from 



Under 

 tained within the glass tube A 

 corrections for the small quantity of 

 the radium B in the glass tube, and also for the absorption 

 of the rays from radium C by the Avails of the glass tube. 

 The method of applying these corrections will appear later. 



