Prof. Majocchi on the Origin of the Voltaic Current. 103 



the electric current in the voltaic apparatus. For adhesion, 

 we know, is not only manifested between solids, as the metals,' 

 but also between a solid and a liquid or aeriform fluid. And 

 many facts of chemical reactions meet with easy explanation 

 from such a force, by which affinity appears to be excited and 

 thence the electrical current to arise, which determines a de- 

 composition and a new combination. However long a time, in 

 fact, a mixture of hydrogen and oxygen is left to Itself, these 

 gases do not combine even when placed in presence of bodies 

 which have a great affinity for water, and which, it would 

 seem, ought to produce their union, as for instance sulphuric 

 acid, potass, lime and the like. We know that if a piece of 

 platina be immersed in the mixture their combination follows 

 on the metallic surface, and extends in certain cases to the 

 whole aeriform mass, so as to cause the explosion of the mix- 

 ture. Grove himself recognises an analogy in the pheeno- 

 menon of his gas battery and that of the ordinary combination 

 ot the two gases, oxygen and hydrogen, by means of the 

 presence of platina. The decomposition of ammoniacal .^as 

 by means of incandescent copper is one of the few instances 

 m which the decomposition of a gaseous body is excited 

 by a solid body. The attraction of gold for chlorine excites 

 the decomposition of nitric acid united with hydrochloric 

 acid when gold-leaf is placed in aqua regia ; for aqua recria 

 only contains free chlorine after being heated, or after havin^ 

 been lett to itselt for a long lime. Numerous other facts ol" 

 this nature have been collected by Mitscherlich* and related 

 m the Reports of the Royal Academy of Berlin, of December 

 1841, and other similar ones by Reiset and Millon communi- 

 cated to the Royal Academy of Paris in June 184-3. All 

 these facts are called by them phcenomena of contact, and Mit- 

 scherlich calls the bodies by which they are produced contact- 

 substances. Berzelius has introduced a new name into science, 

 catalytic force, to denote the cause of adhesion ; but with 

 the new name he has not thrown any light upon the nature 

 of this force. We see in all these facts the adhesion of a solid 

 or a fluid bring into activity the affinity by which, when 

 bodies are conveniently disposed in a complete circuit, elec- 

 tricity is evolved, which then forms a continuous current in 

 tlie mode explained. 



From all that we have said it would follow that, with a 

 sing e iorce, mechanical, chemical or physical, there is only 

 an electrical disturbance, or the phainomena of statical elec- 

 tricity : thus the mechanical action of friction produces in 

 the ordinary machine a simple disturbance of electricity ; the 

 * See Taylor's Scientific Memoirs, Part Xlll. 



