18 NOMOS. 



Taking the power of decomposition as the mea- 

 sure of quantity, Dr. Faraday also found that iodide 

 of potassium was decomposed, and the same amount 

 of iodine set free by this infinitesimal battery in 

 three seconds as by thirty turns of the large machine. 



Now it is extremely difficult to realize the extent 

 of this amazing difference in quantity. The amount 

 produced by thirty turns of the machine, if passed 

 through the head of a cat, is enough to cause instan- 

 taneous death ; and what then must be the amount 

 produced by an ordinary voltaic battery, if the merest 

 fragments of wire can give out in an instant so great 

 an amount ! Dr. Faraday calculates that the amount 

 produced by the battery in the time required to de- 

 compose a single grain of water, will be at least 

 800,000 times as much as that produced by thirty turns 

 of the machine an amount which, if measured at 

 all, can only be measured by all the lightnings of a 

 terrific thunderstorm. Although difficult to realize, 

 however, this difference in the quantity of the two 

 electricities is perfectly real, and if other proof is ne- 

 cessary, it may be found in the common Ley den jar. 

 This jar may be charged indifferently by either elec- 

 tricity, and the signs of charge and discharge in either 

 case are perfectly indistinguishable. The only differ- 

 ence is, that the action of charging by the electrical 

 machine is a matter of time and labour, whereas the 

 act of charging by the voltaic battery is the work of an 

 instant. A mere touch with the poles is enough to 

 charge to the utmost. Now this is as we might ex- 

 pect, if, as is certainly the case, a certain quantity is 

 necessary to the charge, and, being so, the jar not 



