340 ELECTRICITY. 



hand upon the chain, you touch the knob of the 

 jar with a piece of metal held in the other hand. 



Any number of persons may receive the shock 

 together, by laying hold of each other's hands j 

 the first person in the row communicating with the 

 outside of the jar, while the last person touches 

 the knob of the jar which is connected with the 

 inside. In this case, every one will receive the 

 shock at the same instant, and nearly in the same 

 degree, though it may produce a greater effect 

 upon some than upon others. 



The velocity of the electric fluid in passing from 

 a body charged positively, to another charged nega- 

 tively, is beyond all calculation j and from every 

 experiment that has been made, appears to occupy 

 so minute a portion of time, that it cannot be as- 

 certained. It has been sent through a circuit of 

 several miles apparently in an instant, both through 

 water and dry ground. 



It was mentioned above, that the strength of 

 the shock depended upon the quantity of coated 

 surface ; large jars, therefore, give greater shocks 

 than small ones. 



TJw Electrical Battery. 



Several jars may be connected together, by 

 making a communication between all their outsides 

 and all their insides by means of wire or chain. 

 When a number of jars are thus connected, it is 

 called a battery. 



If a battery is required of no very great power, 

 containing about eight or nine square feet of 

 coated glass, common pint or half-pint phials, such 

 as apothecaries use, may be employed. They 



