SKCT. XXIX. THE VOLTAIC BATTERY. 293 



the inner of which is filled with dilute acid, and the one 

 nearer the copper is supplied with crystals of the sul- 

 phate of that metal. The battery consists of several of 

 these elementary cells connected together by metallic 

 wires, the zinc rod of one with the copper cylinder of 

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

 local action, which in ordinaiy 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 possesses con- 

 siderable power, and is constant in its effects for a very 

 long period of time, is greatly superior to all former ar- 

 rangements, either as an instrument of research, or for 

 exhibiting the ordinaiy phenomena of Voltaic electricity. 



A battery charged with water alone, instead of acid, 

 is very constant in its action, but the quantity of elec- 

 tricity it developes is comparatively very small. Mr. 

 Cross of Broomfield in Somersetshire, has kept a bat- 

 tery of this kind in full force during twelve months. 

 M. Becquerel had invented an instrument for comparing 

 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 or- 

 dinary 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 

 combination 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 intensity of the Voltaic electricity is in 

 proportion to the intensity of the affinities concerned in 

 its production, and the quantity produced is in propor- 

 tion to the quantity of matter which has been chem- 

 ically active during its evolution. Dr. Faraday considers 

 this definite production to be one of the strongest proofs 

 that the electricity is of chemical origin. 



Galvanic or Voltaic, like common electricity, may 

 either be considered to consist of two fluids passing in 

 opposite directions through the circuit, or, if the hypoth- 



B B2 



