Applied Science 845 



during the war wireless was used with striking effect, from the 

 small transmitting and receiving wireless sets packed in boxes 

 not more than 18 inches over-all used in the trenches to transmit 

 messages to a base behind the lines, to the contrivances employed 

 to enable ships to find their way through hidden dangers. 



The ship to be guided is provided with two coils of insulated 

 wire, placed one on the port and the other on the starboard 

 side below the water-line. If a telephone is inserted in each 

 of these coils, sounds will be heard in it as long as the ship 

 steers along and near to the cable. If the ship deviates from 

 this course, the sounds become fainter or vanish in one or 

 both telephones. Hence a ship can by this means feel its 

 way along the cable into a harbour or up a river, even at 

 night, or in a fog, or through a minefield. 1 



Lieut.-Col. Slaughter of the United States Army has 

 described how, immediately following the declaration of war by 

 America, orders were issued for an aeroplane wireless telephone 

 set to furnish telephone communication between different aero- 

 planes of a squadron. In May, 1918, "groups of aeroplanes using 

 the wireless telephone sets were being drilled in the evolutions 

 which the equipment made possible. In June, 1918, a squadron 

 of 39 aeroplanes, equipped with wireless telephone sets, went 

 through a course of drill in the air in such a manner as to demon- 

 strate the remarkable possibilities of a voice-commanded squad- 

 ron." Subsequently the training of aviators progressed at a 

 rapidly increasing rate, "so that at the time of the signing of 

 the Armistice many thousands of flights had been made. The 

 record of these flights is a glowing tribute to the efficiency of the 

 design of the wireless telephone set, which performed in such a 

 manner as to give far less trouble than the aeroplane engine." 



We have referred to the number of lives saved by means 

 of wireless messages, and the increased safety it affords to travel- 

 lers by sea. To-day it is unlikely that a disaster of such magni- 



1 J. A. Fleming, Fifty Yean of Electricity. 



