OR VOLTAIC ELECTRICITY. 395 



If such objections to the unity of caloric and 

 electricity were well founded, we should be 

 compelled to admit the existence of more than 

 a hundred species of electricity ; for it differs 

 with every modification of the process by which 

 it is produced, from thermo-electricity of the 

 lowest tension, to that of the Ley den battery, 

 which darts through metals and the living body 

 with the speed of lightning. 



It is known, that the different forms of vol- 

 taic electricity pass with different degrees of 

 velocity through the same conductors ; and that 

 in this respect there is an almost infinite variety in 

 the properties which it presents. Yet these dif- 

 ferences have not prevented Wollaston, Faraday, 

 and many of the most distinguished philosophers 

 of the continent, from maintaining the identity 

 of electricity under every variety of form and 

 appearance which it exhibits, from that of Chil- 

 dren's battery, to De Luc and Zamboni's pile 

 and from a flash of lightning to the magnetic 

 spark, or the shock of a torpedo. Surely there 

 is a far greater difference between the electri- 

 city developed by a common machine and Chil- 

 dren's battery, than between the latter and solar 

 heat concentrated by means of a large burning 

 glass. It was shown by Mr. Parker of Fleet 

 street, that the most intense heat of a burning 

 glass three feet in diameter, though sufficient to 

 fuse and volatilize gems and metals in a few 



