186 Whether Galvanifm be EUBricityf 



a communication be made with an iron key, there is no more appearance of light than in 

 the former inftances. 4. Neither does this efFedl take place if the iron be applied to the 

 eye, and the tin to the tongue, with a communication between them. 5. Gold and filver 

 fcparately applied to thefe two organs, give hardly any fenfation by their contafl. 6. The 

 feme event takes place if two pieces of filver be ufed, and the communication be made by 

 iron. 7. And likewife if copper be placed on the eye, tin on the tongue, and a commu- 

 nication be made by iron. 8. Neither is the fenfatron more evident if the fdver be placed 

 on the eye, the gold on the tongue, and copper be the medium of communication. 9. On 

 the contrary, a confiderable light is feen if the iron touches the eye, the filver the tongue, 

 and the copper forms the communication. 10. Or if gold be fubftituted inftead of filver. 

 II. Or if ihe communication between the iron on the eye, and the gold on the tongue, be 

 made by means of a filver fpatula. 12. Or if the iron on the eye, and the filver on the 

 tongue, communicate dirc£lly. 13. Or if the order of thefe two metals be reverfed. 14. 

 Or if gold be ufed inftead of filver. 15. And laftly, the fame light of the combuftion may 

 be feen, if inftead of placing one of the metals on the tongue, both be placed on the eyes. 



By thefe experiments, which are "all that I recolletl at prefent, and may very eaCly be 

 repeated and varied in different manners, we fee that it is not ele£lricity which produces 

 the refults. For it is well known, that the ele£lric fluid thoroughly and inftantaneoufly 

 penetrates all the mclals which moft eminently condufl it, whatever may be their fituation 

 or relative pofitions. 



But if it be true that the water affords the oxigen to the metal in thefe cafes, it may be 

 demanded, what has become of its hydrogen. It muft be immediately obferved, that on 

 account of the contadl of the atmofphere affording oxigen gas in proportion as the metal 

 confumes it, very little of the water muft be decompofed. 



I have remarked, that I left the different metals for a long time in contaft together, at 

 the end of which I examined them, and I not only found them to be abundantly oxided, 

 but I alfo found regular aluminiform faline cryftals, adhering particularly to the pieces of 

 lilver, and falts of a very determined figure, confifting of two tetrehedral pyramids attach- 

 ed at their bafe, which appeared to me to be hydrogenated tin. 



It is already known that hydrogen diffolves feveral metals; for in hydrogen itfelf are 

 found iron, zinc, arfenic, &c. It Is known, that the amalgam of zinc and mercury con- 

 tains hydrogen, which may be driven off by heat. 



I muft add, that fometimes inftead of placing my apparatus of tin and filver in water, 

 I have left it a long time in alcohol, and found parallellipipedic cryftals upon the 

 fdver, which were very tranfparent, and appeared to contain copper by their light greenifh 

 colour. This copper probably came from the filver; for in general I gave the preference 

 to crown pieces, becaufe I obferve, that the irregularities on their furface occaConed by the 

 impreffion, was greatly favorable to the formation of cryftals which lodged in thefe cavities, 

 and round their edges. I attempted to place the fame metals in ammoniac inclofed in a 

 cryftal bottle, but without any remarkable effeft j probably becaufe the combination of the 



hydrogen 



