370 RECENT PROGEESS IN PHYSICS. 



Hydrogen , 0.37 



Carbonic acid , 0.64 



Olefiant gas 0.75 



while Faraday obtained from a subsequent series of experiments, sim- 

 ilarly arranged, the following values: 



Hydrogen , 0.40 



Carbonic acid 0.78 



Olefiant gas 0.96 



Evidently the corresponding values of m, obtained by positive charges i 

 of s and S , and which should be exactly equal, differ as much from i 

 each other as the corresponding values for the positive and negative •■' 

 charges of s and S; from which it appears that we are justified in assign- i 

 ing no great value to these differences. But there is a further reason < 

 for ascribing these differences to errors of observation, arising from 

 the fact that when air is in the receiver, and the spark accordingly takes ; 

 l)lace throughair, the positive and negative mean values for u are found < 

 unequal, namely: with s and S positive u =z 0.695 ; with s and 8 >. 

 negative u = 0.635. These differences can be ascribed only to acci- i 

 dental disturbances, which produce the errors of observation ; for why 

 should the spark, with a positive charge of s and S, pass more 

 easily through the air at v, and with a negative charge, more easily 

 at u, also through the air? Air being in the receiver, and + and — 

 charges imparted to s and 8, the values for u would be nearly identi- ^ 

 cal, unless the errors of observation were too considerable, 



Faraday himself does not consider these experiments decisive in this 

 respect, but brings forward some facts which seem to indicate some 

 such difference between the positiveand the negative discharge; making 

 w =: 0.8 of an inch, and filling the receiver with muriatic acid gas, 

 the discharge always took place, with a positive discharge of s and S, 

 at u, through air, but with a negative charge of s and S at v, through 

 the muriatic acid gas. 



It also appeared that when the conductor was connected only with 

 the muriatic acid gas apparatus the discharge occurred more readily ' 

 with a negative discharge of the small ball s than with a positive ; for ) 

 in the latter case much of the electricity passed off as brush discharge ; 

 through the air from the connecting wire ; but in the fl^rmer case it ' 

 allseemed to go through the muriaticacid. — (Pog. Ann., XLVII, 287.) 



§ 80. Unequal striking distances of positive and negative discharge.— 

 Many known phenomena coincide in showing that positive and nega- 

 tive discharges do not take place with equal facility. When a small 

 ball, connected with the conductor and thus made inductive, is placed ■ 

 opposite a larger one, which is uninsulated, a spark is obtained twice « 

 as long, the conductor being charged positively, as when negatively i 

 charged. 



Faraday has closely investigated this phenomenon, and obtained 

 the following facts : 



He passed the discharges between two balls of the respective diame- 

 ters of 2 inches and 0.25 of an inch. The larger ball being connected I 



