290 Galvanic Apparatus, Theory of Galvanism, &^e. 



proceeding from the poles of a voltaic apparatus. The particle^ 

 were dispersed from, instead of being attracted to the wires, by 

 which the influence was conveyed among them. This beng tm- 

 dcniable, it can hardly be advanced that we are to have one mode 

 of explaining the separation of the elements of brass by an elec- 

 trical discharge, another of explaining the separation of the ele- 

 ments of water by the same agent ; one rationale when oxygen 

 is liberated from tin, and another when lil)erated by like means 

 from hydrogen. In tlie experiment in which copper was preci- 

 pitated by the same philosopher at the negative pole, we are not 

 informed whether the oxygen. and acid in union with it were at- 

 tracted to the other; and the changes produced in litmus are 

 mentioned not as simultaneous, 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 light is the same. 

 Besides admittingthatthe feeble results obtained byWollastonand 

 Van Marum with electrical machines, are perfectly analogous to 

 those obtained by the galvanic pile, ere it can become an objec- 

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

 between caloric and electricity, whi;-h I suppose productive of 

 galvanic phcenomena, 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 one more I demand, Why, if mechanical electricity be too 

 intense to produce galvanic phaenomena, should it be rendered 

 more capable of producing them by being still more concen- 

 trated? 



If the one be generated more copiously, the other more in- 

 tensely, the .'irst will move in a large stream slowly, the last in a 

 small stream rapidly. Yet by narrowing the channel of the lat- 

 ter, Wollaston is supposed to render it more like the former, that 

 is, produces a resemblance by increasing the supposed source of 

 dissimilarity. 



It has been imagined that the beneficial effect of his contri- 

 vance arises from the production of a continued stream, instead 

 of a succession of sparks; but if a continued stream were the only 

 desideratum, a point placed near the conductor of a powerful 

 machine would afford this requisite, as the whole product may in 

 such cases be conveyed by a sewing needle in a stream perfectly 



continuous. 



