Electric Discharge in Gases. 



41 



_p=08. 



p=x. 



mW 



+ 

 1-6 

 1-3 

 2-0 



1-6 



1-6 

 2-4 



+ 

 0-6 

 10 

 1-5 



0-8 

 0-8 

 1-2 



oW 



F 





The result is here generally the same as with the narrower 

 tubes. With a decreasing number of discharges the heating 

 for equal quantities of electricity increases relatively very 

 little. But if we take the numbers generally and observe that, 

 especially at low pressures, the including of resistances in- 

 creases the number of discharges immeasurably, we see that 

 upon including resistances : — 



(1) The evolution of heat in a gas by a given quantity of 

 electricity which traverses it is almost independent of the 

 circumstance whether it traverses in one discharge or in many. 



(2) Hence, and from the previous result, it follows at once 

 that with two tubes of different diameters, included one behind 

 the other in the same circuit, equal quantities of heat per unit 

 of length are evolved, whether the number of discharges be 

 increased by inserting resistances or not. 



In fact the amount of heating in the narrow and in the wide 

 tubes is scarcely changed by the introduction of resistances ; 

 and since they are the same when no resistances are present, 

 they must also be equal in the other cases. Hence the same 

 laws hold for the normal discharge as for that usually examined. 



In connexion with this the following remarks must be made. 

 Certain advantages possessed by electrophone machines over 

 induction-coils and large galvanic batteries for the investiga- 

 tion of the discharge in vacuous tubes, have been noted by 

 various observers, and in particular by my father and by my- 

 self. Our opinion is based upon the fact that, with the 

 electrophone machines, only the quantity of electricity is dis- 

 charged each time which is required to produce the potential 

 necessary, under the conditions existing in the tube and at 

 the electrodes, to initiate the discharge. 



That these views are not altogether correct is seen from the 

 above ; nevertheless for a number of investigations, and parti- 

 cularly for those of spectroscopic nature, electrophone machines 

 have advantages over other sources of electricity, not only 

 over induction-coils but also galvanic batteries, since with these 

 it is never possible to transmit large quantities of electricity 

 in disruptive discharge without condensers, by the use of 

 which the conditions are much complicated. With the elec- 



