SOUND-RANGING IN THE AMERICAN 

 EXPEDITIONARY FORCES 



AUGUSTUS TROWBRIDGE 



THE following picture is not an imaginary one, but rather 

 one of a very common occurrence throughout the entire 

 period of the war on the long battle front which stretched from 

 the Alps to the sea. 



It is a dark, cloudy night and enemy shells begin to fall 

 near an important point in the trenches or on battalion or regi- 

 mental headquarters. There is a hurried report to our artil- 

 lery and in a few minutes our own guns begin to reply with 

 shells which rend the air or whine as they pass overhead to- 

 ward some invisible mark five miles distant through the black 

 night. Presently the enemy's fire begins to falter and then 

 ceases and the infantryman, whose life may have been saved 

 and whose comfort and efficiency certainly has been protected, 

 may wonder how the artillery knew just where to direct its 

 fire. He knows how it is done in clear weather; how the 

 artillery maintains advanced lookout posts from which observa- 

 tions are made on the flash of the nearer enemy guns; that 

 there are other and more elaborate lookouts on high ground 

 or in trees or towers on the forward edge of woods from which 

 accurate triangulation on the more distant hostile batteries may 

 be made; but he knows that these cannot be the means em- 

 ployed in rain, mist or fog and he probably ends by dismissing 

 the question with the thought that it was only a case of good 

 luck. 



The chances are that even his officers have no clear idea of 



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