means of obtaining Continuous Electrical Oscillations. 255 



through the sleeve in one marble end. This carbon is kept 

 in slow rotation by an electric motor geared to it so that it 

 makes one rotation in about 2 or 3 minutes. In apposition 

 to this carbon is a hollow brass tube closed at both ends, 



Fig. 1. 



having cold water circulating through it. This passes through 

 the other marble end, and it is terminated by a copper beak. 

 The electric arc is formed between this beak and the sharp edge 

 of the rotating carbon. The copper electrode can be moved 

 to and fro by an adjusting screw, and is so set that the arc 

 is formed in a magnetic field between the soft iron pole 

 pieces. The magnetic field is created across the arc by 

 setting the brass box upon an electro-magnet and joining its 

 poles to the two iron cylinders by suitable soft iron con- 

 nectors. With this apparatus it is possible to create an 

 electric arc of suitable length in an atmosphere of coal-gas, 

 the arc being also traversed by a magnetic field. The 

 carbon is the negative and the copper beak the positive pole 

 The field used did not exceed 1000 c.G.s. units in strength. 



