1908] 



on the Carriers of Positive Electricity. 



185 



determine e/m for the ordinary ions was as follows. A tube repre- 

 sented in Fig. 6 was sealed on to the tubes such as have already been 

 described in connexion with the determination of e/m for the Canal- 

 strahlen. B is an ionization chamber, the gas in it being ionized by 

 cathode rays coming down through the tube C which was connected 

 with the earth. The cathode was at D in front of the tube, the 

 anode in a side tube F. Three parallel electrodes, L, M, N, were put 

 in the ionization chamber. The first, L, was -d plate at the top of the 

 tube ; the second, M, near the bottom of the tube was a piece of 

 wire gauze about '^a :millimetre above N, which was the top of an 



mmmm 



Fig. 6. 



earth-connected cylinder, with a small hole • 9 mm. in diameter bored 

 through the centre, the thickness of this plate was 1-6 mm. By 

 means of these electrodes ions could be collected and some of them 

 sent through the hole with a definite and known velocity. Suppose 

 for example we wish to send a stream of positive ions through the 

 hole. A small difference of potential (in our experiments generally 

 that due to two Leclanche cells) was maintained between the plates 

 L M, L being at the higher potential. The electric field produced 

 in this way caused a stream of slowly moving positive ions to pass 

 downwards through the gauze ; by means of a potential divider any 

 potential-difference between 10 and 800 volts could be established 



