A Note qf'M. A. Van DeeTc. 47 



is wanting of the absence of chemical action. In experiments in 

 which zinc is concerned, much caution is required not to fall into 

 error relative to its effects. Though incapable, I beHeve, of de- 

 composing pure water, whether cold or boiling, like iron, yet it has 

 this power, when the water is strongly impregnated with saline 

 matter, as I have witnessed, on immersing polished zinc in a 

 strong solution of its sulphate, hydrogen being disengaged and 

 oxide of zinc formed ; and, farther though incapable of decompo- 

 sing water in a weak saline solution, such as sea- water, yet if asso- 

 ciated with another metal negative to it in electrical relation as 

 platinum, it acquires the power. I'his I have ascertained by 

 several experiments, using sea-water containing air, and also 

 deprived of air, both by the air-pump and by the action of iron. 

 Immediately, on the immersion of two wires of these metals, 

 joined, minute bubbles of gas appeared about the platina wire, 

 the disengagement of which rest on rather increasing in rapidi- 

 ty, and which when collected in sufficient quantity for examina- 

 tion, in the course of two or three days, proved to be hydrogen. 



The application of these results to the instances in question 

 is obvious, especially to the experiment of M. PfafF, in which 

 were conjoined the two circumstances imparting power to the zinc, 

 namely, a strong saline solution and the contact of a negative 

 metal. In the other experiment, that of M. Matteuci, it is pos- 

 sible that the saline mater in the muscles of the frog, though 

 washed v/ith distilled water, or even merely the contact of the 

 muscles themselves, might have exercised a similar influence. 



The only example I have met with in my own experience, 

 of electrical action, indicated by the galvanometer, referrible 

 merely to contact, independent apparently altogether of chemi- 

 cal change, or change of temperature, has been afforded by the 

 immersion of silver and iron wires in a solution of protomuriate 

 of tin, saturated with tin. Steel wire and platina wire previous- 

 ly introduced, had no effect on the galvanometer, indicating 

 therefore the absence of chemical action ; but, substituting a sil- 

 ver wire for the platina, a distinct though slight effect was pro- 

 duced on the needle ; and as the silver wire was negative, it may 

 be inferred to have taken place without chemical change. 



The same result has been obtained, using a neutral solution 

 of muriate of zinc. Silver wire and steel immersed in this, aff- 



