300 VOLTAIC ELECTRICITY. SECT. XXIX. 



next to it. The zinc rods are amalgamated, so that local action, 

 which, in ordinary cases, is so destructive of the zinc, does not 

 take place, and no chemical action is manifested unless the 

 circuit be completed. The rods are easily detached, and others 

 substituted for them when worn out. This battery, which pos- 

 sesses considerable power, and is constant in its effects for a very 

 long time, is greatly superior to all former arrangements, either 

 as an instrument of research, or for exhibiting the ordinary phe- 

 nomena of Voltaic electricity. 



A battery charged with water alone, instead of acid, is constant 

 in its action, but the quantity of electricity it develops is com- 

 paratively very small. Mr. Cross, of Broomfield in Somerset- 

 shire, kept a battery of this kind in full force during twelve 

 months. M. Becquerel had invented an instrument for compar- 

 ing the intensities of the different kinds of electricity by means 

 of weights ; but, as it is impossible to make the comparison with 

 Voltaic electricity produced by the ordinary batteries, on account 

 of the perpetual variation to which the intensity of the current is 

 liable, he has constructed a battery which affords a continued 

 stream of electricity of uniform power, but it is also of very 

 feeble force. The current is produced by the chemical combina- 

 tion of an acid with an alkali. 



Metallic contact is not necessary for the production of Voltaic 

 electricity, which is entirely due to chemical action. The inten- 

 sity of the Voltaic electricity is in proportion to the intensity of 

 the affinities concerned in its production, and the quantity 

 produced is in proportion to the quantity of matter which has 

 been chemically active during its evolution. Dr. Faraday con- 

 siders this definite production to be one of the strongest proofs 

 that electricity is of chemical origin. 



Galvanic or Voltaic electricity is manifested by two continuous 

 forces or currents passing in opposite directions through the 

 circuit : the zinc is the positive end or pole of the battery, and 

 the copper the negative. 



Voltaic electricity is distinguished by two marked characters. 

 Its intensity increases with the number of plates, its quantity 

 with the extent of their surfaces. The most intense concentration 

 of force is displayed by a numerous series of large plates : light 

 and heat are copiously evolved, and chemical decomposition is 

 accomplished with extraordinary energy ; whereas the electricity 

 from one pair of plates, whatever their size may be, is so feeble 



