Dynamic Equivalent of Current FAectricity. 65 



mical action is taking place at any cross section of the cur- 

 rent (in other words, the quantity of the current)^ and the 

 electro-motive force with which the current is sustained, 

 which may be briefly termed its energy or intensity (provided 

 the idea of quantity be kept distinct from this.) The first 

 object is to secure such units of comparison for both these 

 elements as should be at all times recoverable. This is 

 given, in respect of quantity, by the rate of chemical action, 

 and by the atomic weights. In respect of the intensity of the 

 current, we have no such fixed data, and the intensity of 

 most voltaic arrangements cannot be relied on as constants 

 for comparison. 



But the elements of DanielVs battery, and those of nitric 

 acid batteries with negative surface of platinum, carbon, or 

 cast-iron, give an electro-motive force or intensity that can 

 be recovered with considerable exactitude, if uniformity of 

 circumstances, materials, &c., be moderately attended to ; 

 these, therefore, may be used to give a fixed and recoverable 

 point in a galvanometric scale of intensity. 



Now, it so happens, that if we assume the degrees of the 

 scale to be of such a size that the intensity of Daniell's (stan- 

 dard) elements shall be 60% the temperature being 70° Fah- 

 renheit, that of nitric acid batteries will be from 100 to 112 

 of the same degrees. I have, therefore, always used this 

 scale, to which all other voltaic arrangements can be refer- 

 red (as shewn in the table at the end of this paper), and 

 which, I would suggest, would be most conveniently used in 

 assigning the electro-motive power of electric currents from 

 any source. 



The mean result of careful experiments, tried directly 

 and conversely, is, that a voltaic current of one unit in quan- 

 tity (or that from one grain of zinc electro-oxydized per mi- 

 nute), and of 100° intensity, represents a dynamic force of 

 302^ pounds raised one foot high per minute. This datum is 

 of great interest, as a scientific truth, in connection with the 

 other correlative agents of nature, — heat, electricity, light, 

 chemical affinities, neuralgic power, &c., most of which we 

 may hope soon to see reduced to a mutually comparable rela- 



VOL. L. NO. XCIX. — JANUARY 1851. E 



