Trowbridge — Electric Discharges through Hydrogen. 341 



Art. XXVIII. — Discharges of Electricity through Hydro- 

 gen', by Joiln Trowbridge. 



1. Reflection of Cathode Rays. 



2. Striae. 



3. A method of rectification of alternating discharges. 



4. The Doppler effect. 



Reflection of Cathode Rays. 



In the course of this paper I shall refer to certain hydrody- 

 namic analogies which the discharges of electricity through 

 gases present ; but not with the conviction that in these 

 discharges we have to deal solely with questions of flow. 

 The complicated phenomena give large scope both to theories 

 of flow and molecular theories ; the hydrodynamical analogies 

 are more striking in discharges through gases at comparatively 

 high pressures ; while molecular theories apply best in highly 

 rarefied gases. There seems to be a certain continuity here 

 similar to that between motions of matter in the liquid state 

 and in the gaseous state, when such matter is subjected to 

 forces that can produce movement or flow of the particles. 



The condition of electrical discharges in a tube represented 

 in fig. 1 remind one of the flow of a fluid, interrupted by a 



Fig. 1. 



plane lamina. A is a cathode, K an anode, D sl diaphragm, 

 P a plane lamina which can be moved about an axis perpen- 

 dicular to the plane of the paper : fig. 1 being a plan of the 

 discharge tube. P can also serve as an anode. 



At the striae stage the electrical conditions in the tube are 

 very little modified by turning the lamina through small incli- 

 nations to the 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, p. 94 and p. 111). 

 It is also analogous to the conditions presented by the impact 

 of wind on sails fronts. 



Am. Jour. Sci.— Fourth Series, Vol. XXIX, No. 172. -April, 1910. 

 23 



