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If then we wish to enhghten this department of knowledge by 

 the torch of mathematical reasoning, we must beware of proceeding 

 from data either trivial or false ; and must store our minds with 

 experiments, by which we may try our conclusions. For this I am 

 not yet prepared ; and, before I conclude, I shall mention some facts, 

 connected with the V'oltaic apparatus, which are not generally known. 

 The intervals between the plates should be as small as possible ; 

 for, according to my view of the subject, the plates of fluid are 

 charged : and, with a given intensity, the charge is inversely as the 

 thickness, and experience confirms this conclusion ; for it is known, 

 that the pile, notwithtsanding its various imperfections, is much 

 more powerftil than the trough, while the series is small. Nor is 

 any thing gained, by making the cells large, towards the longer 

 continuance of electrical action ; as a battery ceeises to act pow- 

 erfully long before all the acid contained in them is saturated. This 

 diminution of effect is in part owing to the presence of a salt of 

 zinc ; for, if we add a little chlorid of zinc to a mixture of hydro- 

 chloric acid and water, which would have produced a vivid effect, it 

 is rendered nearly inert. But it is still more occasioned by the pre- 

 sence of hydrogen gas ; which virtually diminishes the surfaces of 

 the plates, and of course lessens the quantity of electricity. The 

 troughs, which I have already mentioned as capable of fiising 6 

 inches of fine iron wire Avhen first charged, after 3 minutes could 

 only ignite one. The plates were then raised, and, after two hours, 

 when they were again immersed, it ignited 3t ; and this difference 

 was not owing to any subsidence of the metallic salt, for the fluid 

 was agitated in the cells before the plates were let down. The re- 

 lative values of these impediments may be estimated from the 

 following experiment. A trough, charged with water, contain- 

 ing 7s of hydi'ochloric acid, gave, by decomposing solution of 



