66 THE NEW WORLD OF SCIENCE 



sary the establishment of a large force for compiling and com- 

 paring data from photographs and for disseminating informa- 

 tion to all the various interested services. The profound 

 effects which were produced by the gas warfare were patent 

 to every man on the front and the same was true to a less 

 degree of the camouflage and some of the other services men- 

 tioned, but the very existence of one of these, sound-ranging, 

 was not suspected by most of the troops engaged. This was not 

 because it was in its way less important than the others or be- 

 cause it was working less effectively but rather because it was 

 the policy of the Allies to shroud this particular scientific activity 

 in the most complete secrecy. For this reason, even now" 

 not only the general public but also the majority of those who 

 were over there knows very little of the methods and achieve- 

 ments of the sound-ranging service. As these methods possess 

 a considerable scientific interest and as these achievements have 

 been very creditable it is quite fitting that some account of them 

 should be included in this volume. 



HISTORY 



After the first Battle of the Marne the operations on the 

 western front soon took on the character of siege warfare ; the 

 artillery of both of the belligerents was augmented, especially 

 as regards the larger calibers and the batteries took up well- 

 organized positions carefully concealed for the most part from 

 visual observation by the enemy. 



The possibilities of visual observation had been vastly im- 

 proved by the use of the airplane in war, but these were some- 

 what restricted both by the practice of camouflage and by the 

 generally unfavorable atmospheric conditions on the western 

 front Experiments were therefore undertaken by the French 

 in the autumn of 1914 with the object of ascertaining whether 

 the location of hostile guns by means of sound waves might 

 prove feasible. It was probably not expected that a high de- 

 gree of accuracy would be attainable because of the disturbing 

 effect of wind and temperature irregularities, but the desir- 



