WIRELESS TELEGRAPH 



6325 



WIRELESS TELEPHONE 



sun sends to the earth electric waves as well 

 as light waves, but we are blind so far as elec- 

 tric waves are concerned; our eyes cannot per- 

 ceive them. Such waves are sent out not only 

 by the sun but by every stroke of lightning 



ARLINGTON NAVAL. STATION 

 From Arlington, across the Potomac River 

 from Washington, the government \\ire- 



less messages to American warships on duty ut 

 sea, and to this station nav\ end their 



reports. The Arlington station is the most power- 

 ful in the world, with a range of 3,000 miles over 

 water. One of its towers is 600 feet high, the 

 other two 450 feet each. 



and every spark from an electric machine or 

 induction coil; yet for centuries men did not 

 know of the existence of this peculiar kind of 

 light. It was James Clerk Maxwell in England 

 who first stated that there are such waves, yet 

 Maxwell was unable to (let r<t tin in. He could 

 only prove by mathematics that such waves 

 exist, and that they travel with the same speed 

 as light. It was II< mnrli II- :/. in dcm. 

 who first invented a detector to hcsc 



waves to the human eye and ear. The detector 

 made by Herts was the beginning of wireless 

 telegraphy, though like the beginning of most 

 inventions it was too crude for practical use. 



i liy 



Edward Branly in Paris in 1890. In 1894 V 

 coni in Italy began his experiments which 

 to the practical wireless telegraph. 



Uses of Wireless Telegraphy. Perhaps the 

 most important use of wireless telegraphy i> 

 that of sending messages across the sea and to 

 and from ships at sea. In saving life in disas- 

 ters at sea by calling relief to sinking vessels 

 wireless telegraphy has been of service beyond 

 estimation. The disasters to the Republic, 

 the Titanic, the Monroe and the Empress of 

 Ireland serve as recent instances in which tin 

 loss of life would have been more appalling 

 but for the call of distress heard over leagues 

 of stormy seas. It is used also to a large ex- 

 tent in sending commercial messages overland. 

 This is true particularly between important cen- 

 ters, to relieve the congestion of the wire tele- 

 graph service, and after storms, when telegraph 

 wires are down. Another important use of the 

 wireless telegraph is the combination of the 

 wireless with an aeroplane. The aeroplane car- 

 ries an aviator and a wireless operator. In the 

 War of the Nations aeroplanes so equipped ob- 

 served the enemy and kept commanding offi- 

 cers informed as to his movements. K.K.H. 



Consult Pierce's Principles of Wireless Teleg- 

 raphy ; Senneck's Wireless Telegraphy; Bccles* 

 Wireless Telegraphy and Telephony. 



Related Subject*. The reader is referred to 



the following articles in these volumes: 

 Induction Coil 

 Leyden Jar 



Magnet and Magnetism 

 Telegraph, subhead 

 The Codes 



Battery 



Current, Electric 

 Electricity 

 Electrode 

 Electrolysis 

 Induction, Electric 



WIRELESS TELEPHONE, td'cfokn, a de- 

 vice by which the sounds uttered by the hu- 

 man voice can be transmitted hundreds of 

 miles without any medium of transmission 

 cept the air. To be told that a person in pos- 

 session of the proper mechanism may in any 

 place of his choosing converse with a friend 

 similarly equipped, wherever he may be, within 

 reasonable distance, seems like a fairy tale. 

 In- feat has been accomplished. Much of 

 the pioneer work in the ii. 

 device is (o the credit of Gugliclmo Marconi. 



One method of producing electric waves suit- 

 able for wireless telephony is by means of an 

 electric air. The arc is operated by a direct 

 current and takes the place of the spark gap 

 of tl h sec), but a 



special arrangement is needed to cause an clec- 

 arc to send out electric waves. A con- 

 ! !i-r and a coil having ':on (sec 



. .Tiilr) must I- icrOBS 



the terminals of the arc. The theory is that 

 when the circuit is completed across the arc 



