whither Galvanifm he caufed by Ele&ricUy, &c. jeg 



I afterwards obferved, that feveral metals were not only charged with oxide, but that 

 fmall faline cryftals of different figures were formed. It appeared therefore to me, that an 

 evident chemical a£lion had taken place, and that it was unneceflary to feek farther for the 

 nature of the new ftimulus, which in the experiment of Sultzer has been called galvanifm. 

 It was manifeftly a combuflion or oxidation of the metal ; the ftimulating principle might 

 tlicrefore be either the caloric, which is difengaged, or the oxigen, which pafles to new 

 combinations; or laftly, the new metallic fait: but which of thefe it may be I have not 

 well afcertained. I have in fome inftances coloured the water, in which I placed the metals 

 with tournfol; but I have remarked no other efFeft, than a precipitation of that colouring 

 fecula, without any change of its colour. I have remarked, that the water in which this 

 experiment is made, contrafts a flight metallic, or as I may fay, arfenical tafte ; which 

 lafls for fome time, and produces a difpofition to fpit ; but it does not appear to contain 

 enough of metal to be detected by the mod fenfible chemical re-agents. I have therefore 

 thought it proper to limit my conclufions refpe£l;ing this phenomenon, that it is merely a 

 flow combuftion of the metal, which muft be accompanied with an attraftion of oxigen, 

 and a developement of light and caloric. It is well known that when a metal, fuch for 

 example as gold, is amalgamated with mercury, there is an immediate expulfion of caloric, 

 not perhaps in coiifequence of the folid ftate of the mercury, but becaufe the diminution 

 of the force of aggregation in the particles of the latter metal facilitates its combuftion. 

 The progrcflive augmentation of weight which is obfervable in amalgams, arifes only from 

 the oxigen which they attra£l from the atmofphere. I attempted in vain to meafure the 

 quantity of caloric, which is developed by the contadl of two folid metals, whatever may 

 be their weight. This quantity is too fmall and too diffufed, as it were, over a large fur- 

 face, to be afcertained by inftruments of fo little delicacy as thofe we poflefs. Never- 

 thelefs, the light which flows from this metallic combulion, may be feen if the eye forms 

 part of the apparatus. For example, it is only requifite to hold a piece of filver in the 

 mouth, and apply a fmall piece of tin upon the ball of the eye ; as foon as thefe two metals 

 are made to communicate dire£l;Iy, or even by means of a third metal, a faint, but very 

 diftincl light is perceived, which is not an eleflric fpark, nor a convulfive irritation. For 

 though this light appears to affeft the organ at the firft inftant only, becaufe the eye foon 

 becomes accuftomed to this weak fenfation, we may be alTured, that the emanation of light 

 is continual in this cafe, by Aiding alternately the tranfparent and the opaque cornea againft 

 the metal, when it will be feen that the light is ftronger whenever the metal is touched by 

 the more tranfparent part of the organ. And again, if this experiment be made as it 

 ought in the dark, nothing more will be necelTary, than to attend at the time when the 

 communications between the two metals is interrupted, and the obfcurity will be more deep 

 and perfeft, which is a proof of the conftant prefence of fome light before that interrup- 

 tion. I do not fpeak of that kind of flafh which fome perfons affirm they have feen, by 

 applying the two metals fimply to the tongue and the gums, without the eye forming part 

 of the circuit. I have not been able to verify this faft on myfelf, and have remarked, that 



>R 2 feveral 



