1821.] Dr. Hare: & new Gahanic Apparatus, Theory, ^c. 335- 



separated from each other, and appearing in their distinct 

 metaUic colours." In the next page of the same work, I find 

 that the oxides of mercury and tin are reduced by electrical dis- 

 charges. " Introduce," says the author, ** some oxide of tin 

 into a glass tube, so that when the tube is laid horizontal, the 

 oxide may cover about half an inch of its lower internal surface. 

 Place the tube on the table of the universal discharger, and 

 introduce the pointed wires into its opposite ends, that the por- 

 tion of oxide may lay between them. Pass several strong 

 charges in succession through the tube, replacing the oxide in 

 its situation, should it be dispersed. If the charges are suffi-^ 

 ciently powerful, a part of the tube will soon be stained with 

 metallic tin which has been revived by the action of transmitted 

 electricity." It cannot be alleged that in such decompositions 

 the divellent polar attractions are exercised like those which 

 characterize the action of wire proceeding from the poles of a 

 voltaic apparatus. The particles were dispersed from, instead 

 of being attracted to the wires, by which the influence was con- 

 veyed among them. This being undeniable, it can hardly be 

 advanced that we are to have one mode of explaining the sepa- 

 ration of the elements of brass by an electrical discharge, ano-^ 

 ther of explaining the separation of the elements of water by the 

 same agent. One rationale when oxygen is liberated from tin, 

 and another when liberated by like means from hydrogen. In 

 the experiment in which copper was precipitated by the same 

 philosopher at the negative pole, we are not informed whethei!' 

 the oxygen and acid in union with it were attracted to the other, 

 and the changes produced in litmus are mentioned not as simul- 

 taneous, but successive. The violet and red rays of the spectrum 

 have an opposite chemical influence in some degree like that of 

 voltaic poles, but this has not led to the conclusion that the 

 cause of galvanism and hght is the same. Besides admitting 

 that the feeble results obtained by Wollaston and Van Marum. 

 with electrical machines are perfectly analogous to those ob- 

 tained by the galvanic pile, ere it can become an objection to 

 my hypothesis, it ought first to be shown that the union between 

 caloric and electricity, which I suppose productive of galvanic 

 phenomena, cannot be produced by that very process. If they 

 combine to form the galvanic fluid when extricated by ordinary 

 galvanic action, they must have an affinity for each other. As 

 I have suggested in my memoir, when electricity enters the 

 pores of a metal, it may unite with its caloric. In Wollaston's 

 experiments, being constrained to enter the metal, it may com- 

 bine with enough of its caloric to produce, when emitted, results 

 slightly approaching to those of a fluid in which caloric exists in 

 greater proportion. 



But once more I demand why, if mechanical electricity be 

 too intense to produce galvanic phenomena, should it be ren- 



