SECT, xxix.] DECOMPOSITION OF WATER. 339 



electricity has been most successfully applied to the art of 

 plating and gilding, as well as to the more delicate process 

 of copying medals and copper plates. Indeed, not medals 

 only, but any object of art or nature may be coated with 

 precipitated metal, provided it be first covered with the 

 thinnest film of plumbago, which renders a non-conductor 

 sufficiently conducting to receive the metal. 



Common electricity, on account of its high tension, passes 

 through water and other liquids as soon as it is formed, 

 whatever the length of its course may be. Voltaic elec- 

 tricity, on the contrary, is weakened by the distance it has 

 to traverse. Pure water is a very bad conductor; but ice 

 absolutely stops a current of Voltaic electricity altogether, 

 whatever be the power of the battery, although common 

 electricity has sufficient power to overcome its resistance. 

 Dr. Faraday has discovered that this property is not peculiar 

 to water ; that, with a few exceptions, bodies which do not 

 conduct electricity when solid acquire that property, and 

 are immediately decomposed, when they become fluid ; and, 

 in general, that decomposition takes place as soon as the 

 solution acquires the capacity of conduction, which has led 

 him to suspect that the power of conduction may be only a 

 consequence of decomposition. 



Heat increases the conducting power of some substances 

 for Voltaic electricity, and of the gases for both kinds. Dr. 

 Faraday has given a new proof of the connexion between 

 heat and electricity, by showing that, in general, when a 

 solid, which is not a metal, becomes fluid, it almost entirely 

 loses its power of conducting heat, while it acquires a ca- 

 pacity for conducting electricity in a high degree. 



The galvanic fluid affects all the senses. Nothing can be 

 more disagreeable than the shock, which may even be fatal 

 if the battery be very powerful. A bright flash of light is 

 perceived with the eyes shut, when one of the wires touches 

 the face, and the other the hand. By touching the ear with 

 one wire, and holding the other, strange noises are heard ; 



z 2 



