Fluid Galvanic Battery. 269 



were connected with a pair of coke-points. The voltaic current 

 passed through the two empty cells, ignited the coke-points, and 

 produced a brilliant light. The voltaic current had no other 

 means of passing to the coke than through the damp pieces of 

 wood which separated the zinc plates from the cast-iron cells, or 

 through the wooden frames in which the two empty cells were 

 placed. 



The Rev. Dr. Robinson and Mr. Rergin, to whom I men- 

 tioned the various fluids which I found to excite cast iron and 

 zinc so powerfully, have lately tried a cast-iron battery of 48 

 cells, charged with one part of strong sulphuric acid and three of 

 a pretty strong solution of common salt. The distance between 

 the zinc and iron was nearly ^th of an inch. The quantity of 

 fluid used in filling the battery was, I think, a gallon and a 

 half, in which there were about three pints, or about seven 

 or eight pounds of sulphuric acid. With this battery they 

 had a brilliant coke light sufficiently steady to enable them 

 to make observations on the light with the prism and polari- 

 scope; also lights produced by the ignition of various me- 

 tallic points, on which lights similar observations were made. 

 Various other experiments were made ; they commenced at one 

 o'clock, and were not given up till nine. There were of course 

 several interruptions, during each of which the fluid was, by a 

 very ingenious contrivance, poured off the metallic plates. During 

 the eight hours the experiments lasted, the battery was in con- 

 stant action at least three and a half or four hours. At the end 

 of the experiments the two metals were quite clean, and there was 

 no sensible diminution of voltaic power. Such is the substance 

 of the account which I received of the action of this battery. The 

 results of this trial of the battery show that a cast-iron battery, 

 excited by one part of sulphuric acid and three of a solution of 

 common salt, is very powerful, extremely constant in its action, 

 and most oeconomical in use. The sulphuric acid employed was 

 made, not from pyrites, but from sulphur. I purchase, at the vitriol 

 works of Messrs. Boyd, Belfast, sulphuric acid made in the same 

 way, and of the same strength, at the rate of 8s. 6d. per cwt., or 

 for less than one penny per pound. Hence at the price at which 

 sulphuric acid is sold by Messrs. Boyd, the cost of the exciting- 

 fluid for eight hours' experiments scarcely exceeded eight pence. 

 I have also got from Messrs. Boyd for 3s. 6d. per cwt., weak but 

 pure muriatic acid of the specific gravity 1-130, which I have 

 found to answer for the cast-iron battery better without being 

 diluted, than strong muriatic acid diluted with a small quantity 

 of water. 



The cast-iron battery excited by any of the fluids which I 

 have mentioned, is superior in power to any of the nitric acid 



