RECENT PROGRESS IN PHYSICS. 



Striking distance in Paris lines. 



405 



If we indicate by 1 the density of the electricity which is distributed 

 upon the ball C when the plate B is charged while A is removed, 

 more electricity will be attracted from C to B when the condenser 

 in connexion with the ground is brought within two lines of the plate 

 B, and thus the density of the electricity on C is diminished to 0.105. 



The influence which the condenser A exerts upon the induction of 

 electricity on the opposite insulated system B C, naturally depends 

 upon the distance between A and B ; the further A is from B, so 

 much the less will the density on be diminished on its elevation. 



From a numerous series of experiments, conducted as those above 

 described, Riess found for different distances of the condenser the 

 following striking distances at the ball 0, the striking distance with- 

 out the condenser being taken as unity. 



Distance of plates.. i 2 lines. 

 Striking distance.... 0.105 



5 lines. | 10 lines. ; 20 Knes. 

 0.272 I 0.451 ! 0.687 



30 lines, i 50 lines. 00 

 0.794 0.914 1 



If we suppose that a perfectly free communication of electricity can 

 be made at the knob C of the normal connecting wire, an accumula- 

 tion of electricity will occur on the plate so long as the striking dis- 

 tance at the knob does not exceed a given quantity. Make this limit 

 of density equal to 1 . Suppose the insulated system, B standing alone, 

 is charged to this limit. Now, if the condenser be brought near, and 

 more electricity thus attracted to the plate B, and its density on C 



diminished, (say to — ,) it is clear that n times as much electricity 

 n 



can be conveyed to the whole insulated system as before, until the 

 density 1 is reached on C ; hence the apparatus, in the presence of 

 the condenser, can receive n times as much electricity as before. 



In the above experiments, the density of the electricity on C is di- 

 minished by the approach of the condenser within two lines, to 0.105 



or ; hence an accumulation of electricity 9.5 times as great as 



9.5 J G 



without the condenser. 



•For the different distances of the condenser in the above experiments 

 the possible increase of density on the collector is in the following pro- 

 portion : 



