09 Theory of Galvanic Eleclric'ity, 



cither in closing or opening the chain, which is contrary id- 

 t+ie opinion of VoUn: there is here wanting, he says, the 

 essential condition, being the humid, between the two he- 

 terogeneous metals. 



lu the second experiment he plunges the metallic plate 

 into vessels where he has put salt water, and the electricity 

 is augmented when we increase the quantity of the liquid 

 in the vessels so as to make it touch a greater surface of the 

 metals. He calls to mind'lhe similar experiments of Messrs. 

 Dcsormcs and Van Marum, who have also concluded that 

 the size of the humid surfaces contributes much to the 

 strength of the pile. 



M. Heidman afterwards endeavours to determine the 

 power of the difierent fluid conductors, according to the 

 degree of their chemical action. 



For example, having placed two prepared frogs, in such 

 ?. manner that their nerves were inserted in watch-glasses 

 in which different liquids had been placed, such as a solu- 

 tion of alkaline sulphuret on one side, and water on the 

 other side; the communication of the two fluids being esta- 

 l^lished by a metallic wire, he observed that, at the moment 

 of the formation of the chain, it was the muscle on the side 

 of the first of these liquors which was contracted, and that 

 from the moment of the rupture of the chain it was the 

 muscle on the side of the water alone which suffered the 

 contraction. 



In order that he might not be led into error by the stimu- 

 lant action peculiar to some liquors, and particularlv to the 

 acids, he took care to interpose, between the nerve and tlve 

 liquor, a piece of fi.sh well soaked lii water. 



In this manner he submitted to experiment all the dif- 

 ferent liquids already known as conductors of ordinary 

 electricity, and he has arranged them in the following 

 order, relative to their chemical power and their Galvanic 

 action : ' - 



Acids — oxvmuriatic. 



■ muriatic, impregnated with azote- 



muriatic. 



Solution of oxymuriatc of potash. 



Acids 



