GALVANISM. 



the cells O, and pure water in L. A series of eight metallic plates produced 

 sensible effects. Copper was the most active of the metals tried, and lead the 

 least so. In thJse cases, the terminal wires produced, in the usual manner, 

 the d<?compositii of water, the wire from which hydrogen was evolved being 

 that which was connected with the end of the series to which the surfaces of 

 ihe metal not chemically acted on were presented. 



It will be observed that in this case the direction of the electric current 

 relatively to the surfaces of the metallic plates was the reverse of the former. 

 When oxydation was produced, the oxydating sides of the plates looked toward 

 the negative end of the series. Comparing these two effects, Davy was led 

 by analogy to suspect that if the cells O were filled with an oxydating solu- 

 tion, while the cells L were filled with a solution of sulphuret, or any other 

 which would produce a like chemical action, the combined effect of the cur- 

 rents proceeding from the two distinct chemical processes would be obtained. 

 This was accordingly tried, and the results were as foreseen. The acid solu- 

 tion was placed in the cells O, and the sulphuret in the cells L. A series, 

 consisting of three plates of copper or silver, arranged in this way, produced 

 sensible effects ; and twelve or thirteen decomposed water rapidly. The 

 oxydating sides of the metal looked to the negative end of the series. 



As it appeared from former experiments the charcoal possessed, as a Voltaic 

 agent, the same properties as the metals, the next step in this course of ex- 

 periments was naturally to try whether a Voltaic arrangement could not be 

 constructed without any metallic element, by substituting charcoal for the me- 

 tallic*plates in the series above described. This was accomplished by means 

 of an arrangement in the form of the couronne des tosses. Pieces of charcoal, 

 made from very dense wood, were formed into arcs ; and the liquids O and L 

 were arranged in alternate glasses, as represented in fig. 2. The charcoal 



arcs C were placed so as to have one end immersed in each liquid, the inter- 

 mediate glasses being connected by slips of bibulous paper P. When the 

 liquid O was dilute acid, and L water, a series consisting of twenty pieces of 

 charcoal gave sensible shocks, and decomposed water. This arrangement 

 also acted, and with increased intensity, when the liquid O was sulphuric acid, } 

 and L was solution of sulphuret of potash. 



The connexion of chemical change with the production of electricity in the 

 pile, was too obvious not to attract the attention of other philosophers. Pepys 

 in England, and MM. Biot and Frederic Cuvier in France, investigated the 

 effect produced by the pile on the atmosphere in which it was placed. The 

 former placed the pile in an atmosphere of oxygen, and found that in the 

 course of a night 200 cubic inches of the gas had been absorbed. In an at- 

 mosphere of azote the pile had no action. MM. Biot and Cuvier also observed 

 5 the quantity of oxygen absorbed, and inferred from their experiments that 

 I " although, strictly speaking, the evolution of electricity in the pile was pro- 

 ) duced by oxydation, the share which this had in producing the effects of the 

 \ instrument bore no comparison with that which was due to the contact of the 

 metals, the extremity of the series being in communication with the ground." 



Dr. Wollaston and Gautherot, on the other hand, reproduced the principle 

 ) advanced by Fabroni and Creve. WoUaston maintained that chemical action 

 { 



