122 Prof. Thomson, Do the 7 rays carry a charge 



To test whether the secondary rays are or are not the source 

 of the electrification observed in Paschen's experiments I tried the 

 experiment represented in the figure. 



A and B are two cylinders equal in all dimensions, made of 

 thin brass, but while A is hollow, B is filled with lead. These 

 cylinders, which are in electrical connection, are supported on an 

 insulating rod of fused quartz and placed in a symmetrical position 

 inside a large glass bulb coated with tin-foil. A gold-leaf electro- 

 scope was attached to the middle of the cylinder A. The radium 

 (30 mg. of radium bromide) was outside the glass vessel, it was 

 placed far back in a cylindrical cavity drilled in a lead cylinder, 

 the opening of the cavity was closed by a plate of lead 2 mm. thick 

 to absorb the /3 rays. This arrangement gave a pencil of y rays 



