358 Mr. Faraday's Experimental Researches in Electricity. 



§ 8. Relation by Measure of common and voltaic Electricity, 



361. Believing the point of identity to be satisfactorily esta- 

 blished, I next endeavoured to obtain a common measure, or 

 a known relation as to quantity, of the electricity excited by 

 a machine, and that from a voltaic pile ; for the purpose not 

 only of confirming their identity (378.), but also of demon- 

 strating certain general principles (366. 377, &c), and creat- 

 ing an extension of the means of investigating and applying 

 the chemical powers of this wonderful and subtile agent. 



362. The first point to be determined was, whether the 

 same absolute quantity of ordinary electricity, sent through a 

 galvanometer, under different circumstances, would cause the 

 same deflection of the needle. An arbitrary scale was there- 

 for attached to the galvanometer, each division of which was 

 equal to about 4°, and the instrument arranged as in former 

 experiments (296.). The machine (290.), battery (291.), and 

 other parts of the apparatus were brought into good order, 

 and retained for the time as nearly as possible in the same 

 condition. The experiments were alternated so as to indicate 

 any change in the condition of the apparatus and supply the 

 necessary corrections. 



363. Seven of the battery jars were removed, and eight re- 

 tained for present use. It was found that about forty turns 

 would fully charge the eight jars. They were then charged 

 by thirty turns of the machine, and discharged through the 

 galvanometer, a thick wet string, about ten inches long, being 

 included in the circuit. The needle was immediately deflected 

 ^\e divisions and a half, on the one side of the zero, and in 

 vibrating passed as nearly as possible through five divisions 

 and a half on the other side. 



364. The other seven jars were then added to the eight, 

 and the whole fifteen charged by thirty turns of the machine. 

 The Henley's electrometer stood not quite half as high as be- 

 fore; but when the discharge was made through the galvano- 

 meter, previously at rest, the needle immediately vibrated, 

 passing exactly to the same division as in the former instance. 

 These experiments with eight and with fifteen jars were re- 

 peated several times alternately with the same results. 



365. Other experiments were then made, in which all the 

 battery was used, and its charge (being fifty turns of the 

 machine,) sent through the galvanometer : but it was modi- 

 fied by being passed sometimes through a mere wet thread, 

 sometimes through thirty-eight inches of thin string wetted 

 by distilled water, and sometimes through a string of twelve 



