concerned in the Phenomena of ordinary Electricity, 6fc. 339 



dimensions can endure : the conducting power of the water can 

 only affect the velocity of the discharge, not the intensity of the 

 charge. The difference of the dimensions of the strings will 

 cause scarcely any difference of intensity in their charge, so ex- 

 ceedingly small is their surface compared with that of the coating 

 of the Leyden battery. The surface of Faraday's battery being 

 3150 square inches, a thread 38 inches long and ^thof an inch 

 diameter will expose a surface 630 times less than the battery. 

 The battery, therefore, being in all the three cases charged with 

 fifty turns of the plate-machine, will impart the same intensity 

 to the strings; and these will communicate the same intensity 

 Of charge to the galvanometer coil. As intensity is quantity 

 compared to space, it follows that as the intensity in all the 

 three cases is the same, so is the quantity in the coil at any par- 

 ticular instant of time; and so must be the deflection. But the 

 state of the coil at the first instant would determine the swing 

 of the needle ; for the needle reaches its extreme deviation, not 

 entirely in consequence of the true deflecting power of the elec- 

 tricity transmitted, but partly by the momentum which it has 

 acquired from the first impulse ; and before this ceases to act, 

 or while the needle is in the condition of being constrained to 

 resume its place by the power of terrestrial magnetism, the whole 

 discharge will have taken place, no matter whether it occupied 

 " a sensible time " only, or " two or three seconds." 



Thus the velocity of the discharge from the Leyden battery, 

 although modified by the thickness, length, and humidity of the 

 string, has nothing to do with the intensity of the electricity 

 which passes. One charge may pass more slowly than another, 

 by meeting more resistance from the nature of the conducting 

 substance, and yet be of the same intensity. The difference of 

 time must, however, always be exceedingly small. 



In another experiment, the battery of fifteen jars was charged 

 by sixty revolutions of the machine, and discharged as before 

 through the galvanometer: "the deflection of the needle was 

 now as nearly as possible 44°," but the graduation was not accu- 

 rate enough to determine that the arc was exactly double the 

 former arc ; to " the eye it appeared to be so." This result was 

 expected : the charge in the battery was double, and the inten- 

 sity of electricity in the galvanometer coil, through which the 

 whole charge passed, was consequently doubled : no wonder, 

 then, that the force which was to produce deflection of the needle 

 was also doubled ; but I shall have to make further observations 

 on this experiment hereafter. We may therefore deny tliat the 

 intensity was different in any of the experiments; and we are 

 not bound to admit, that " if the same absolute quantity of elec- 

 tricitv pass through the galvanometer, whatever may be its in- 



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