t4* On ike EffeSs of the Galvanic Shoth, 



■ Col. Haldane's apparatus confided of forty half crowns, with an equal number of pieces of 

 zinc, and 39 cards, which were wetted with pure water. They were placed horizontally 

 on a table, and the experiment of decompofing water by two copper wires, was repeated 

 and defcribed with minute accuracy. 



He did not receive a fliock with wetted hands, nor fee any light when the tohgne formed 

 one of the extremes of the circuit ; but his fpn was ftruck with this laft appearance. 

 Neither did his apparatus affeA the eleftrometer of 'BenAet, nor my fpining inftrument. 

 When a fewing needle was pafied beneath the Ikin of a finger of one hand, and another 

 needle inferted in like manner in the other hand, and thefe were made the extremities of 

 the circuit, a fharp irritation was felt at the wounded parts, with a convulfive fenfation, 

 extending to the flioulders,«and 'even the neck., But this did not refemble the eleftric 

 fliock, being more unpleafant, and of longer duration. 



The decompofition of water by filver, and by gold wires, was attended with phenomena 

 fimilar to thofe defcribed in our former numbers. The gold wire fuffered decompofition. 



In the examination of the pile, he found its power diminiftied by diminiftiing the num- 

 ber of pieces ; that it would not aft -if either of the three plates were omitted ; that tinfoil 

 inftead of filver a£l:ed tolerably well ; and that leather was preferable to card. 



When the apparatus was imraerfed in water, its adlion was intirely fufpended ; but upon 

 taking it out and wiping the exttrnal furface, without feparating the parts, it afted as well 

 as before. Hence I am dlfpofed to conclude, that the power of the Colonel's apparatus 

 was confidcrably impaired by his placing them horizontally, which muft have favored the 

 efflux of water from the cards, and theftce between the faces of the zinc and filver: whence 

 his failure in the flieck and ele£lric figns. For the upright pile is certainly much ftronget 

 than a pile which has been immerfed in water and then wiped. 



The apparatus was fufpended in the receiver of an air pump, which was then exhaufled 

 of air, till the mercury in the gage flood at half an inch. The decompjdtion of water ia 

 •a tube with copper wires, did not proceed during this ftate, but was renewed when the air 

 was let in. 



This author has tried combinations of the various metals,' and finds that zinc will a£t 

 with gold, tin, lead, iron, and copper; that iron will a£l with the fame metals, as will 

 alfo lead, though feebly. But no other combinations of thefe metals would anfwer, except 

 that tin and gold afforded a very faint cloud in the water. When iron and filver were ufed,. 

 the oxidation took place at the wire connefted with the iron, and the gas flowed from that 

 connected with the filver ; but the contrary happened when zinc and iron were ufed, which 

 afted very powerfully, as in this cafe the iron connexion afforded the gas. And he con» 

 fiders it as worthy of remark, that the oxide of copper wire depofited in the tube was of a: 

 dufky coloured green, different from that produced by the apparatus of zinc and filver, as 

 if fome parts of the metals compofing the apparatus had entered into the circulation, and 

 affe£led the colour of the oxide. This obfervation is undoubtedly very curious, and de- 

 feives U> be purfued; but I fllould. be inclined to fuppofe, that the degree of oxidation 



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