220 Mr Orange, On certain phenomena of the kathode region. 



at a later stage ; this was attained by having a small bulb con- 

 taining dry sodium formate in connection with the apparatus and 

 heating to 250° C. when the hydrogen was required. 



The kathode is shown separately in Fig. 2 ; it was made of 

 aluminium and carried on a lead of the same material protected 

 by a glass tube. 



An induction-coil with the common interrupter maintained the 

 discharge and in the usual way a condenser was connected to the 

 interrupter, but it was found necessary (with the higher gas 

 pressures at least) to insert a ' point and plane ' spark gap in the 

 secondary circuit, to secure freedom from reversals. 



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IT 



IT 



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fMamMrm»MrMWMMM0rirj^jrmM0MMMMf0r»rMMMm00A' 



Fig. 2. 



At first it was thought that sufficiently accurate records of the 

 appearance of the discharge could be obtained by sketching, but 

 owing to the glare this was painful to the eyes and did not give 

 very satisfactory results. Recourse was then had to photography 

 and as a rule little difficulty was encountered. The camera 

 employed could be extended considerably and consequently could 

 be set up very near to the discharge-tube, so that photographs 

 were obtained of nearly natural size. Using Imperial Ortho 

 plates, exposures of from 2 to 5 minutes were given, the aperture 



being -. 



Fig. 1, PI. IV*, shows the peculiar appearance of the kathode 

 region when the Crookes' dark space envelopes only the corners of 

 the triangle. [Cp. Kunz, loc. cit. Fig. 16.] 



* It should be noted that certain features of these photographs are quite acci- 

 dental, being reflections from the glass discharge vessel, e.g. the eye-shaped patch 

 of light opposite the shortest side of the triangle, and two rectilinear markings 

 opposite the side of intermediate length. 



Further, the positive column, which extends a variable distance down into the 

 bulb, should be clearly distinguished. 



