1908] The Carriers of Positive Elertricity. 171 



WEEKLY EVENING MEETING, 



Friday, April 10, l'J08. 



The Right Hox. Lord Rayleigh, O.M. P.C. D.C.L. 

 liL.D. F.R.S., in the Chair. 



Peofessor Sir J. J. Thomson, M.A. LL.D. D.Sc. F.R.S. M.EJ. ; 



Professor of Natural Pliilosophj, Royal Institution. 



The Carriers of Positive Electricity. 



Though the ordinary cathode rays are the most conspicuous of the 

 rays spreadins; out from the cathode in a vacuum-tube, there are 

 other rays mixed with them, which as Goldstein * and the writer f 

 showed long- ago are not appreciably deflected by weak magnetic 

 fields. The very complete study of the region near the cathode made 

 by Goldstein, the results of which are described in a paper read before 

 the Physical Society of Berlin, J has led him to distiuguish five kinds 

 of rays besides the cathode rays. Recent experiments made by Vil- 

 lard§ and the author || have shown that some of these rays are deflected 

 in electric and strong magnetic fields, and the direction of the de- 

 flexion indicates that they carry a positive charge of electricity. The 

 fact that these positively charged rays travel with high velocities away 

 from the cathode, and thus against the direction of the electric force, 

 makes the investigation of their properties a very interesting problem, 

 and I have lately made a series of experiments with the object of ob- 

 taining some information as to their nature and origin. 



The tube used in the first series of experiments is represented in 

 Fig. 1. A is a perforated electrode through which rays can pass on 

 their way to the phosphorescent screen S covered \vith Willemite ; 

 the rays on their journey to the screen traverse strong electric and 

 magnetic fields, the former produced by charging the plates L M to 

 different potentials and the latter by placing the tube between the 

 poles of a powerful electromagnet. From the deflexions which these 

 produce on the rays, the velocities and values of e/in for the rays can 

 be determined in the usual way. B is a flat electrode at the other 

 end of the tube ; this electrode is carried by a stopper working in a 

 ground-glass joint, and can be rotated about a vertical axis. C is an 

 auxiliary electrode at the side of the tube. D is a side tube in which 



* Verhandl. d. Deutsch. physik. Gesellsch. iv. p. 228, 1902. 



t Proc. Camb. Phil. Soc. ix. p. 243. % Republished Phil. Mag. Mar. 1908. 



§ Comptes Rendus, cxliii. p. 673, 1906. jj Phil. Mag. xiv. p. 359, 1907. 



