238 Our Surroundings 



called tuning. It will help you to understand this process if you 

 consider the action of two pianos near each other. When they 

 are tuned to the same pitch, a note struck on one piano will 

 produce the same tone on the corresponding wire of the other. 

 They are in tune and therefore vibrate, or oscillate, in sympathy. 

 In a similar way, the apparatus of a receiving radio station must 

 be in tune with the apparatus of the sending station; otherwise 

 communication will not be effective. 



Everyday Radio. The radio sets just described are very 

 simple ones. The big broadcasting and receiving sets have many 

 complicated parts. These consist mainly of little refinements 

 which serve to clarify tone, magnify volume, eliminate inter- 

 ference, and perform other helpful services. The parts named 

 are those essential for radio sending and receiving. 



Radio is playing an increasingly greater part in the lives of 

 millions of citizens. Every day, scores of stations broadcast con- 

 certs, lectures, stock reports, weather forecasts, and news to any 

 who care to tune in. Football games and World Series baseball 

 games, once enjoyed by relatively few, are now broadcast play- 

 by-play throughout the entire country. 



The latest development in radio is known as television. It 

 consists in sending the sound as in regular broadcasting and also 

 projecting a moving picture on a screen attached to the receiving 

 set. With this equipment one can hear whatever is being broad- 

 cast and see the broadcasters at the same time. 



SUMMARY 



Among the chemical effects due to electricity are electrolysis, 

 electroplating and electrotyping. 



Electrolysis is the process of breaking up a compound into 

 its elements by passing an electric current through it. 



Electroplating is coating a metal with another metal. 



Electrotyping is the making of printing plates from type. 



Electric heating is producing heat by means of electricity. 



Electric lighting is producing artificial light by electricity. 



Fuses are pieces of metal which melt at a moderate tempera- 

 ture, and are used to safeguard an electric circuit. 



