SOUND-RANGING 87 



before the close of the war to locate enemy guns by employing 

 two or more sound-ranging sections working together, so that 

 each might give an accurate determination of line and by com- 

 bining these to obtain an accurate determination both of line 

 and range. 



An idea may be gained of the amount of artillery information 

 supplied by the sound-ranging sections from the following 

 figures taken from a report of the artillery information officer 

 of one of the American Corps. This officer had as sources of 

 information American sound- ranging sections, and American 

 and French flash-ranging sections. During a period of rapid 

 advance 425 separate locations of enemy batteries were made; 

 of these two American flash sections reported 63 per cent., 

 three French flash sections 16 per cent, and three American 

 sound sections 21 per cent. In a period of two weeks when the 

 advance had been temporarily checked by the enemy the total 

 number of locations was 392 and the percentages were : three 

 American flash sections reported 38 per cent., two French flash 

 sections reported 8 per cent, and three American sound sections 

 54 per cent. 



In another and very active sector, where there was but one 

 American sound section and one American flash section, the 

 figures were : during a period of three days preparation for an 

 advance, sound 22 locations, flash 22, balloons o, aviation o. 

 During a period of sixteen days rapid advance, sound 4, flash 

 46, balloons 30, aviation 15. During a period of four days of 

 stabilization, sound 6, flash 34, balloons 13, aviation 15. These 

 figures are fairly characteristic and bring out clearly the rela- 

 tively great importance of sound-ranging during the stationary 

 warfare and of visual observation during actual attack. This 

 was to be expected as sound-ranging was devised to meet the 

 peculiar conditions of trench warfare. When, in the spring 

 of 1918, it became apparent that a more open warfare was 

 beginning, the sound-ranging sections were trained and 

 equipped so as to become as mobile as the -artillery of the 

 heavier calibers but they never were able to get in action so 



