424 



RECENT PROGRESS IN PHYSICS. 



knobs, in spite of the little resistance still due to the rarefied 

 air, a spark can no longer pass. The air having regained its ordinary 

 density between the knobs, a considerable approximation of the latter 

 is necessary to make another discharge possible. By discharging at 

 the striking distance, therefore, the electricity is successively trans- 

 mitted. 



K A proof of this successive discharge exists in the fact that the re-^ 

 mainder of the charge is considerably greater, and consequently 

 a smaller quantity of electricity disappears if the first discharge oc- 

 casions a break in the circuit, as is the case, for instance, when a fine 

 wire, interposed in the circuit, is fused which we will consider more 

 at length hereafter. 



A further proof of successive discharge at the striking distance is 

 the circumstance that the residual charge is considerably greater when 

 a tube of water is introduced into the circuit. 



Instead of the copper or platinum wire mentioned on page 420;, the 

 glass tube with water was interposed, and a series of experiments with 

 this circuit gave the following results : 



Although the striking distance here is the same under like circum- 

 stances, as in the metallic circuit, the quantity of electricity Inat dis- 

 appears is much less than when the metallic circuit is used. With 



the latter ^ = H == 0.846, with the water it is only I = 0.625 ; the 



remainder of the charge then. amounted to yV = 0.154; in this case 

 it is f = 0.3*75 ; thus the residue is here more than double as great 

 as in the former case. 



Riess explains this in the following manner : A battery being 

 charged, the quantities of electricity on the outer and inner coatings 

 are in a given ratio to each other. An excess on the inner coating, 

 which is an aliquot part of the whole quantity, exists in the 

 interior. The quantity of induced electricity on the exterior coating 

 is also in a certain ratio to this excess. At the first moment of the 

 discharge equal portions of the electricity of the inner and outer 

 coatings disappear, the former ratio is destroyed, and there. is now 

 proportionally more free electricity on the inner coating than in the 

 state of perfect charge, and in this way a further discharge is favored; 

 But when the tube of water is introduced the discharge is so delayed 



