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PROCEEDINGS OF THE AMERICAN ACADEMY. 



line of discharge. The striae remain practically unaffected in shape 

 and position until the angle between the normal to the lamina and the 

 axis of flow reaches 50°. This phenomenon is analogous to the case 

 of a lamina subjected to the flow of a liquid (Lamb's Hydrodynamics, 

 pages 94 and 111). It is also analogous to the conditions presented 

 by the impact of wind on vanes. 



By means of a side adjunct a thermo pile, T, was introduced in 

 order to measure the heat excited by the reflection of the cathode 

 rays passing through the diaphragm D and reflected from the lamina, 



Figure 2. 



when the latter was inclined to the axis of the cathode rays at varying 

 angles. Here also there was an action similar to the reflection of a 

 stream of liquid from the lamina, proceeding in the direction of the cath- 

 ode rays. The angle between the normal to the lamina and the axis 

 of flow or discharge could vary largely without affecting the amount 

 of heat from the reflected cathode beam shown by the thermopile. 



2. Stride. 



The striae, or stratifications, in Geissler tubes constitute a very beau- 

 tiful and mysterious phenomenon of the discharge of electricity 

 through gases, and if one could follow the mechanism involved per- 

 fectly one could feel sure of having penetrated far into questions of 

 the method of propagation of electricity. There seems no reason to 

 doubt that the striae are phenomena of ionization ; but the regularity 



