212 A new Theory of Galvanism. 



citement may be detected in the apparatus by the condensing 

 electroscope; but this is no more than what Volta observed to be 

 the consequence of the contact of heterogeneous metals. 



The thinnest piece of charcoal intercepts the calorific agent, 

 whatever it may be. In order to ascertain this, the inside of a 

 hollow brass cylinder, having the internal diameter two inches, 

 and the outside of another smaller cylinder of the same substance, 

 were made conical and correspondent, so that the greater would 

 contain the less, and leave an interstice of about one-sixteenth 

 of an inch between them. This interstice was filled with wood, 

 by plugging the larger cylinder with this material, and excavat- 

 ing the plug til! it would permit the smaller brass cylinder to be 

 driven in. The excavation and the fitting of the cylinders was 

 performed accurately by means of a turning lathe. The wood in 

 the interstice was then charred by exposing the whole covered 

 by sand in a crucible to a red heat. The charcoal, notv/ith- 

 standing the shrinkage consequent to the fire, was brought into 

 complete contact with the inclosing metallic surfaces by pressing 

 the interior cylinder further into the exterior one. 



Thus prepared, the exterior cylinder being made to touch one 

 of the Galvanic surfaces, and a wire brought from the other Gal- 

 vanic surface into contact with the outside cylinder, was not 

 affected in the least, though the slightest touch of the interior 

 one caused ignition. The contact of the charcoal with the con- 

 taining metals probably took place throughout a surface of four 

 square inches, and the wire was not much more than the hun- 

 dredth part of an inch thick ; so that, unless it were to conduce 

 electricity about forty thousand times better than the charcoal, 

 it ought to have been heated, if the calorific influence of this ap- 

 paratus result from electrical excitement. 



I am led finally to suppose, that the contact of dissimilar me- 

 tals, when subjected to the action of solvents, causes a movement 

 in caloric as well as in the electric fluid, and that the phseno- 

 mena of Galvanism, the unlimited evolution of heat by friction, 

 the extrication of gaseous matter without the production of cold, 

 might all be explained by supposing a combination between the 

 fluids of heat and electricity. We find scarcely any two kinds of 

 ponderable matter which do not exercise more or less affinity 

 towards each other. Moreover, imponderable particles are sup- 

 posed highly attractive of ponderable ones. Why then should 

 we not infer the existence of similar affinities between imponde- 

 rable particles reciprocally? That a peculiar combination between 

 heat and light exists in the solar beams, is evident from their not 

 imparting warmth to a lens through which they may pass, as do 

 those of our culinary fires. 



Under this view of the case, the action of the poles in Gal- 

 vanic 



