44 CONTEMPORARY SCIENCE 



pelling machinery; and this energy is five times greater 

 than the maximum average developed on the Western 

 Front by British guns. Furthermore, if all her guns were 

 fired simultaneously, they would for the instant be de- 

 veloping energy at the rate of 13,132,000 horse-power. 

 From these figures we can form some conception of the 

 vast destructive energy developed in a modern naval 

 battle. 



Engineering and the War. 



Sound-ranging and Listening Devices. Probably the 

 most interesting development during the war has been 

 the extensive application of sound-listening devices for 

 detecting and localizing the enemy. The Indian hunter 

 puts his ear to the ground to listen for the sound of the 

 footsteps of his enemy. So in modern warfare science 

 has placed in the hands of the sailor and soldier elaborate 

 instruments to aid the ear in the detection of noises 

 transmitted through earth, water, air, or ether, and also 

 in some cases to record these sounds graphically or photo- 

 graphically, so that their character and the time of their 

 occurrence may be tabulated. 



The sound-ranging apparatus by which the position of 

 an enemy gun can be determined from electrically re- 

 corded times at which the sound wave from the gun 

 passes over a number of receiving stations, has enabled 

 our artillery to concentrate their fire on the enemy's guns, 

 and often to destroy them. 



The French began experimenting in September, 1914, 

 with methods of locating enemy guns by sound. The 

 English section began work in October, 1915, adopting 

 the French methods in the first instance. By the end of 

 1916 the whole Front was covered, and sound-ranging 

 began to play an important part in the location of enemy 

 batteries. During 1917 locations by sound-ranging 

 reached about 30,000 for the whole army, this number 



