244 Prof. Thomson, On the Cathode Rays. [Feb. 8, 



along the cathode rays. The following experiments show however 

 that there must be something besides a stream of negatively 

 electrified particles along the cathode rays. If the coil is kept 

 running the negative charge in the cylinder does not increase 

 indefinitely, it reaches a certain limit and then remains constant, 

 though the cathode rays keep pouring into the cylinder, and 

 further if the inner cylinder be charged negatively to begin with, 

 then if this charge exceeds a certain amount, though the insulation 

 is perfect when the rays are not playing upon the cylinder, yet as 

 soon as the rays fall upon it some of the negative charge escapes. 



In the experiments on the magnetic deflection of the rays, the 

 rays were produced in a side tube and sent into a large bell jar 

 through a slit in a metallic plate. The bell jar was placed between 

 two coils arranged as in a Helmholtz galvanometer so as to pro- 

 duce a uniform magnetic field. The rays in their course through 

 the bell passed in front of a glass plate ruled into squares. 

 A large number of photographs of the rays were taken in different 

 gases and at various degrees of exhaustion. The following were 

 some of the results obtained. 



The magnetic deflection of the cathode rays in air, hydrogen, 

 carbonic acid gas and methyl iodide is the same provided the 

 mean potential difference between the cathode and the anode is 

 the same. 



Coming through the slit there are certain ' rays ' which are 

 not deflected by a magnet : these have little if any power of pro- 

 ducing phosphorescence. The path of the rays for the first part 

 of their course was very approximately circular. 



(2) On Electricity in Gases and the formation of Clouds in 

 Charged Gases. By J. S. Townsend (M.A. Dub.). 



1. Of all the electrical phenomena with which we are 

 acquainted there are few more interesting from a scientific point 

 of view than those which are to be found in gases. The branch of 

 the subject which is treated of in this paper is that which is 

 related to the properties of gases having an electrostatic charge. 

 No attempt is made here to give an account of the different 

 methods that have been employed to charge gases, as it is my 

 intention merely to enumerate some of the more important results 

 arrived at while investigating this subject. 



2. Even with their rough methods of detecting electrification 

 Laplace and Lavoisier knew that the hydrogen evolved when a 

 metal dissolves in an acid carries with it a charge. It is therefore 

 all the more remarkable that with the present delicate methods of 

 detecting electric charges the question of electrification by natural 

 processes, in contradistinction to artificial methods should have 



