THE SMALLEST WORKERS 



appliances, you are sure to have an electric call-bell. 

 The generator of the electric current, which is stored 

 away in some out-of-the-way corner, is probably a 

 small so-called " dry-cell" which you could readily 

 carry around in your pocket; or it may consist of a 

 receptacle holding a pint or two of liquid in which some 

 metal plates are immersed. Such an apparatus seems 

 scarcely more than a toy when we contrast it with the 

 gigantic dynamos of the power-house; yet, within the 

 limits of its capacities, one is as surely a generator of 

 electricity as the other. If we are to accept the latest 

 theory, the electrical current which flows from this tiny 

 cell is precisely the same in kind as that which 

 flows from the five-thousand-horse-power dynamo. 

 The difference is only one of quantity. 



To understand the operation of this common house- 

 hold appliance we must bear in mind two or three 

 familiar experimental facts in reference to the action 

 of the voltaic cell. Briefly, such a cell consists of two 

 plates of metal for example, one of copper and the 

 other of zinc with a connecting medium, which is 

 usually a liquid, but which may be a piece of moistened 

 cloth or blotting-paper. So long as the two plates of 

 metal are not otherwise connected there is no electricity 

 in evidence, but when the two are joined by any metal 

 conductor, as, for example, a piece of wire thus, in 

 common parlance, "completing the circuit " a current 

 of electricity flows about this circuit, passing from the 

 first metal plate to the second, through the liquid and 

 back from the second plate to the first through the piece 

 of wire. The wire may be of any length. In the case of 



