PHYSICS OF NINETEENTH CENT. ELECTRICITY. 555 



discovered the power of the pile to decompose salts, and to cause in 

 certain cases their constituent metals to be deposited in the solid form. 

 Experiments in voltaic chemical decompositions were now everywhere 

 repeated, and as will be found stated in relation to the history of 

 chemistry, an important theory and new classification of substances, 

 based on their electrolytic properties, were proposed by Davy and 

 Berzelius. 



Davy at once entered eagerly into an experimental investigation of 

 the powers of the pile. We find him in October, 1800, propounding 

 very distinctly the chemical theory of the pile. He declares that gal- 

 vanism is a purely chemical action, depending entirely on the oxida- 

 tion taking place at the metallic surfaces, upon which the solution acts 

 in different degrees. If the plates are moistened with perfectly pure 

 water, the pile will not act, because pure water does not act upon zinc, 

 and, in fact, the electrical power of the pile is always proportionate to 

 the energy with which the oxidizable metal is acted upon. 



The original forms of the voltaic pile and the couronne de tasses 

 were united into one in the arrangement invented by Cruikshank. We 

 may think of this as a horizontal instead of a vertical pile, with moistened 

 discs replaced by liquid strata, or as the couronne de tasses, with the 

 metallic connections between the plates so abbreviated that the copper 

 of one cell and the zinc of the next are soldered to each other back to 

 back, and themselves constitute the walls of the cells which contain the 

 liquid. " Cruikshank's battery " is the simplest of all voltaic arrange- 

 ment. The double plates of copper and zinc are of a rectangular 

 form, and are cemented into grooves in the bottom and sides of a long 

 rectangular trough, which they divide into so many cells. The ex- 

 citing liquid is poured into these cells. The simplicity of this arrange- 

 ment at once permitted voltaic piles, or batteries, as we more frequently 

 call them, to be conveniently made of a far greater number of elements 

 than had before been used. In February, 1802, Pepys had made a 

 battery of sixty pairs of plates 6 inches square. Experiments with 

 this revealed new and wonderful powers of galvanism. Iron wires 

 were burned, platinum wires made to glow with an intense light, 

 charcoal was rendered incandescent, gold and silver leaf were defla- 

 grated. 



Other improvements in the arrangement of the plates of copper and 

 zinc in the voltaic battery were effected by Wollaston, and soon after 

 Davy had entered upon the professorship of chemistry at the Royal 

 Institution, the managers had the large Wollaston battery constructed, 

 by which Davy made his famous discoveries of the metals of the alka- 

 lies. This battery contained 250 pairs of plates ; but after Davy had 

 announced his great discovery, another battery of 600 pairs of plates 

 was constructed for the Royal Institution, the cost being defrayed by 

 a subscription of the members. It was with this that Davy succeeded 

 in completely demonstrating the existence of the metallic bases in the 



