THE TELEGRAPH 327 



work of many men before him, who had made discoveries 

 which he used in constructing his instruments. While still 

 but a young man of 2 1 years, he transmitted signals without 

 wires through a distance of two miles. This was in 1896. 

 In 1897 this distance was increased to 18 miles, and in 1899 

 messages were sent across the English Channel, a distance 

 of 32 miles. He next directed his attention to telegraphing 

 across the Atlantic Ocean; and in 1901, a signal was sent 

 from England to Newfoundland, a distance of 1800 miles. 

 These and other stations have been improved until now a 

 number of companies are doing business in sending messages 

 across the ocean. Messages are now sent more than 4000 

 miles. 



Waves. If a stone is thrown into a pond, water waves are 

 sent out and spread in every direction. In a similar manner 

 light and electricity travel by wave motion. Scientists 

 believe that all space is filled with a very thin substance 

 which they call ether. (This has nothing to do with the 

 ether used in medicine.) It is really no more wonderful 

 that electricity should travel through this ether without 

 wires than that light should come to us from the sun. It 

 seems more strange because the light waves affect our eyes, 

 and we are able to see objects by means of the light waves 

 that come from them. Electricity travels by means of waves 

 which we cannot detect through our senses as we can light 

 waves; but instruments have been made which detect 

 these waves. 



Sender. A wireless outfit consists of a sending apparatus 

 to send out electric waves, and a receiving apparatus to 

 receive these waves sent out from another station. The 

 connections of these parts are shown in figure 134. The 

 sending apparatus consists of some source of current elec- 

 tricity such as batteries B, an induction coil 7, Ley den jars, a 

 spark gap , and a key K, to control the current . The induction 

 coil is an instrument by means of which an electric current 



