298 ELCETROGILDING. SECT. XXIX. 



that still water, cooled below 32, starts into crystals of 

 ice the instant it is agitated. Light and motion are 

 intimately connected with electricity, which may there- 

 fore have some influence on the laws of aggregation; 

 this is the more likely, as a feeble action is alone neces- 

 \ sary, provided it be continued for a sufficient time. 

 Crystals formed rapidly are generally imperfect and 

 soft, and M. Becquerel found that even years of constant 

 Voltaic action were necessary for the crystalization of 

 some of the hard substances. If this law be general, 

 how many ages may be required for the formation of a 

 diamond ? 



The deposition of metal from a metallic solution by 

 galvanic 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 metals 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 re- 

 ceive 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. Vol- 

 taic electricity, on the contrary, is weakened by the dis- 

 tance it has to traverse. Pure water is a very bad con- 

 ductor ; but ice absolutely stops a current of Voltaic 

 electricity altogether, whatever be the power of the bat- 

 tery, 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 sub- 

 stances for Voltaic electricity, and of the gases for both 

 kinds. Dr. Faraday has given a new proof of the con- 

 nection between heat and electricity, by showing that 



