CHAPTER XXII 



SIMPLE ELECTRIC DEVICES 



MANY animals possess the power to see, to hear, to smell, to 

 taste, and to feel, but only man is able to build on the in- 

 formation gained through these senses. It is his constructive 

 power that raises man above the level of the beasts and enables 

 him to devise and fashion wonderful inventions. Among the 

 most important of his inventions are those which relate to 

 electricity, inventions such as trolley cars, elevators, auto- 

 mobiles, electric lights, the telephone, the telegraph. Alexandei 

 Bell, by his superior constructive ability, made 

 possible the practical use of the telephone, and 

 Marconi, the wireless telegraph. To these in- 

 ventions might be added many others which 

 have increased the efficiency and production of 

 the business world and have decreased the labor 

 and strain of domestic life. 



Electricity as first obtained by man. Until 

 modern times the only electricity known was 

 that of lightning and that produced by rubbing 

 amber with fur or wool. But in the year 1800, 

 electricity in the form of a weak current was 

 obtained by Volta of Italy in a very simple way. 

 Even now our various electric batteries and 

 cells are but a modification of the voltaic cell used by Volta. 

 A strip of copper and one of zinc are placed in a glass of sul- 

 phuric acid dissolved in water. Sulphuric acid is composed 

 of oxygen, hydrogen, and sulphur. As soon as the plates 



207 



FIG. 73. A simple 

 electric cell. 



