82 THE NEW WORLD OF SCIENCE 



position of the enemy gun could be located but also contained 

 data from which the location of the burst of the shell could 

 be calculated; thus both the range and the time of flight of the 

 shell were known. In the case of guns employing fixed 

 ammunition charge a knowledge of these two quantities was 

 sufficient to determine the caliber of the gun since the values 

 of the muzzle velocities of many of the German guns were well 

 known to the Allies. Even in the case of guns not employing 

 fixed ammunition charge the fact that the burst of the shell 

 could be located enabled the officer in charge of the section 

 to recover fragments of the shell on which to base an estimate 

 of the caliber. 



The possibility of an estimate of the caliber of the enemy 

 guns was one of the unique features of sound-ranging. 

 Another important feature was the ability to locate guns which 

 were brought up by the enemy in preparation for an attack 

 and which were therefor not used in the period preceding the 

 attack in order to insure an element of surprise. Such guns 

 usually fired but one or two ranging shots and if they were 

 well concealed usually escaped detection by ordinary means; 

 many such guns were located by sound-ranging when they fired 

 their first, and often only, ranging shot. 



The location of the enemy artillery formed only one part, 

 though the more important part, of the routine work of a sound- 

 ranging section. When, because of bad weather, aerial or other 

 visual observation was impossible the sound-ranging sections 

 were called on to correct the fire of the friendly artillery on 

 enemy objectives either to silence the fire of batteries or to 

 harass the enemy traffic in the back areas. In the case of 

 silencing the fire of an enemy battery which had just fired, 

 sound-ranging was very effective. The following considera- 

 tion will show why this was so: suppose an enemy gun has 

 just fired and that a record has been obtained by the sound- 

 ranging section; to obtain an accurate location it is necessary 

 to apply temperature and wind corrections to the observed 

 data and it is the lack of accurate knowledge of the wind and 



