Franklin, Dufay and Ampere. 475 



respectively. Admitting that the relative intensity were 

 merely as the length of the spark, not as the square of that 

 length, still there woukl be an infinite difference between the 

 intensity of a voltaic series and that of electrical machines, if 

 measured by this test. Large electrical machines, like that at 

 the Polytechnic Institution, London, give sparks at twenty 

 inches and more ; while, agreeably to Gassiot's experiments, 

 a Grove's battery of 320 pairs in full power, would not before 

 contact give a spark at any distance, however minute. It fol- 

 lows, that, as respects the species of intensity which is indicated 

 by length of sparks, or striking distance, the difference be- 

 tween the electricity of the most powerful voltaic series and 

 electrical machines is not to be represented by any degree of 

 dispariti/; it proves that galvanism proper and electricity 

 proper are heterogeneous. 



47. It should be recollected that the intensity of galvanic 

 action, in a series of S20 pairs, excepting the loss from con- 

 duction, would be to that of one pair as 320 to 1 *. Of course, 

 the striking distance of a battery of one pair would be 320 

 times less than nothing : 320 below zero. 



48. We may infer that the undulatory polarization of aethereo- 

 ponderable matter is the primary, direct, and characteristic 

 effect of galvanic excitement, in its more energetic modifica- 

 tions; yet, that by peculiar care in securing insulation, as in 

 the water batteries of Cross and Gassiot, aethereal undulations 

 may be produced, with the consequent accumulation of eethereal 

 polarity requisite to give sparks before contact, agreeably to 

 the experiments of those ingenious philosophers. 



49. Hence it maybe presumed, that duringintense a^thereo- 

 ponderable polarization, superficial aethereal waves may always 

 be a secondary effect, although the conducting power of the 

 reagents requisite to the constitution of powerful galvanic 



• According to Coulomb's experiments, electrical attraction and repulsion 

 are inversely as the squares of the distances, and the inductive power of 

 statical charges wliich is produced by those forces, and wiiich precedes and 

 determines the length of the resulting spark, must, of course, obey the same 

 law. 



If this calculation be correct, the intensity must be as the squares of the 

 striking distances, as indicated by sparks. 



It may be urged, that tlie striking distances, as measured by the length 

 of the sparks, is in the compound ratio of the quantity and intensity. As 

 to the quantity, however, galvanic sources have always been treated as ])re- 

 eminent in efficacy, so that on that side there could he no disparity. More- 

 over, I have found that in galvanic apparatus of only one, or even of two 

 pairs, as in the calorimotors, the intensity lessened as the surfaces ^vere 

 enlarged. By a pair of fifty square feet of zinc surface, a whho heat could 

 not he produced in a wire ofany size, however small. The calorific power of 

 such aiijiaratus can only be made evident by the production of a compara- 

 tively very low temperature, in a comparatively very large mass. 



