Mr. Ritchie on a Torsion Galvanometer. 35 



plates at the distance of nine and four inches, and gave the 

 deflecting forces in the ratio of 2 to 3, which are the square 

 roots of 9 and 4. After trying the effects of the plates at 

 different distances, the following law was established, which 

 had formerly been obtained by a different process : viz. that 

 the quantity of Voltaic electricity circulating along the metallic 

 conductor connecting two plates of dissimilar metals, is inversely 

 as the square roots of the distances between the two plates. 

 This law was originally deduced by Professor Gumming, by 

 observing the deflection of a compass needle, and then taking 

 the deflecting forces as the tangents of the angles of deviation 

 from the original direction of the needle and straight conductor. 

 When I undertook this investigation, it had escaped my me- 

 mory that any law had been discovered which connected the 

 deflecting force with the distance of the plates. This circum- 

 stance, as well as the different process by which it was deduced, 

 affords the most complete proof of its truth. 



This law is certainly very different from what we might 

 at first have expected. We might, without experiment, 

 have argued thus: If one inch of fluid between the plates offer 

 a certain resistance to the electric current, two inches will pre- 

 sent twice the resistance, three inches three times the resist- 

 ance, 8fc. &c. With regard to the cause of this curious law, 

 we can at present scarcely offer a conjecture. Does the electric 

 fluid, after passing through a certain length of an imperfect 

 conductor, acquire some power which enables it to pass more 

 easily through an equal portion ? There are phenomena in 

 nature in which imponderable agents do acquire such proper-* 

 ties, Light may be so far modified as to pass entirely through 

 glass, which, without such a modification, would have been 

 partly reflected. De Laroche discovered that invisible radiant 

 heat, after passing through a thin plate of glass, passes with 

 less resistance or loss through a second, &c. But, instead of 

 being led away by analogies, which by some may be regarded 

 as fanciful, I shall mention one practical lesson to be deduced 

 from the law in question. In constructing a battery for electro- 

 magnetic purposes, there is not so much power gained as might 

 be supposed by putting the plates very near each other. For 

 example, if the plates are at the distance of a quarter of an 



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