408 WELLS'S NATURAL PHILOSOPHY. 



. Frictional electricity is capable of passing for a considerable 



diffureiicc-s In;- distance through or over a non-conducting or insulating sub- 

 tweeii the two gtance, whicli galvanic electricity can not do. Thus, the spark 

 from a prime conductor will leap toward a conducting sub- 

 Btance for some distance through the air, which is a non-conductor; but if '* 

 current of galvanic electricity is resisted by the slightest insulation, or the in- 

 terposition of some non-conducting substance, the action at once stops. Gal- 

 vanic electricity will traverse a circuit of 2,000 miles of wire, rather than makj 

 a short circuit by overleaping a space of resisting air not exceeding one hun- 

 dredth part of an inch. Frictional electricity, on the other hand, v.'ill force ( 

 passage across a considerable interval, in preference to taking a long circuit 

 through a conducting wire, or at least the greater portion of it will pass 

 through the air, though some part of the charge will always traverse the wire. 



Frictional electricity produces very slight chemical or heating effects ; gal- 

 vanic electricity produces very powerful efliects. 



A proper and simple arrangement of a zinc plate and a little acidulated 

 water, will produce as much electricity in three seconds of time as a Leyden 

 jar battery charged with thirty turns of a largo and powerful plate electrical 

 machine in perfect action. The shock received by transmitting this quantity 

 of galvanic electricity through the animal system would be hardly perceptible, 

 but received from a Leyden jar, would be highly dangerous, and perhaps 

 fatal. A grain of water may be decomposed and separated into its two ele- 

 ments, oxygen and hydrogen, by a very simple galvanic battery, in a very 

 short time; but 800,000 such charges of a Leyden jar battery, as above re- 

 ferred to, would be required to supply electricity sufficient to accomplish the 

 same result. Such a quantity of electricity sent forth from a Leyden jar 

 would be equal to a very powerful flash of lightning. 



rpon what does T^iG quantltj of electricity excited in a gal- 

 vanic^'dectrici- vaiiic circuit is directly proportional to the 

 ty depend? amount of cliemical action that takes place — 

 as between the zinc and the acid. By increasing the 

 amount of surface exposed to chemical action, we there- 

 fore increase the quantity of electricity evolved. 



Hence, gigantic plates have been constructed for the purpose of obtaining^ 

 an immense quantity. 



The intensity of the electricity evolved de- 



Upon what does i /> i i i • 



intensity de- pcnus upon thc niimocrot plates, and isgreat- 

 ^™ est when thc voltaic pile is made up of a great 



number of small plates. 



Supposing an equal amount of surflxce of copper and zinc employed, the 

 shock, and other indications of a strong charge, would be greater if it were 

 cut up into many small circles, than if it formed a few large ones. But the 

 actual quantity of excitement would bo greatest with the large plates. 



