CONQUEST OF TIME AND SPACE 



from the ether waves that we interpret as light except 

 in their length, but in this regard the difference is 

 enormous. The longest wave that is visible to the 

 eye is of such infinitesimal dimensions that 33,000 

 waves are required to span the distance of a single 

 inch. But the electro-magnetic wave with which 

 the wireless operator deals may measure scores or 

 hundreds of miles. Suppose, for example, that the 

 electric current generating the wave oscillates at 

 intervals of the one thousandth of a second. Then, 

 since the wave travels 186,000 miles per second, each 

 wave will obviously be 186 miles in length. In prac- 

 tice, the waves used in transatlantic radiography are 

 between two and three miles in length. 



Such a discrepancy in size being noted, it is not 

 surprising that the electro-magnetic waves used by 

 the wireless have a penetrating power altogether 

 different from that of the tiny light waves. In point 

 of fact the waves that transmit the wireless messages 

 penetrate any substance that lies in their path, includ- 

 ing mountains. Curiously enough, bright sunlight 

 may obstruct the waves, presumably because of the 

 presence of electrons in the atmosphere. 



The possibilities of wireless communication had 

 been conceived by many experimenters. As long 

 ago as 1887 Mr. Thomas Edison proved that mes- 

 sages could be sent to and from a moving train, com- 

 munication being established through the air be- 

 tween the operator on the train and the ordinary 

 telegraph wires along the track. By various other 

 experimenters the possibility of communication with- 

 out wire was considered and more clearly demon- 



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