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OUR FHYSICAL WORLD 



series of vibrations may either be broken into long and short 

 groups, as with the wireless telegraph when transmitting dashes 

 and dots, or modifications made in the nature of the wave so that 

 sounds of various pitch may be transmitted as in the case of 

 the radio telephone. 



A very simple amateur wireless telegraph sending outfit 

 may consist of a source of electrical power, such as a battery, 



* 



k 



FIG. in. A simple wireless sending outfit 



a key for controlling the power, an induction coil and spark gap 

 by means of which the battery current is transformed into high- 

 frequency electrical current, and an antenna or electrical con- 

 ductor extending some distance above the earth, so that the 

 electric waves may readily radiate into the ether with little 

 interference. Such an arrangement is shown by diagram in 

 Figure in. The source of electrical power is shown at (&), and 

 consists of a battery of several cells. The key for interrupting 



