SOUND-RANGING 83 



temperature which causes errors in the location; suppose that 

 instead of attempting to locate the gun the approximate posi- 

 tion is reported to the friendly artillery and a shell is thrown 

 immediately somewhere near the enemy gun and a sound- 

 ranging record is taken of the burst of this shell. If, by 

 chance, the shell had hit the gun the sound-ranging records of 

 the gun and of the burst would be identical, for whatever effect 

 wind and temperature had had on the one record it would 

 also have had on the other. Even though the first shell does 

 not hit the gun it will be near enough so that its relative position 

 to the gun may be accurately calculated from the difference 

 of the two records. If the sound-ranging section commander 

 reports the first shell as so many meters left and so many 

 meters short, for example, the battery commander may correct 

 round after round in this manner until a direct hit is obtained. 

 A technique of rapid calculation was devised which permitted 

 the simultaneous correction of the fire of all four guns of a 

 friendly battery firing salvos. The fall of individual rounds 

 was in practice not reported though they were of course 

 observed but rather the mean point of burst of six or eight 

 rounds of each of the guns was reported; the battery com- 

 mander made his corrections and another series of rounds was 

 fired and new corrections were applied and this was generally 

 sufficient to make it worth while to fire for effect. This method 

 of ranging was only employed when the simpler visual methods 

 were impossible as it necessitated a partial suspension of the 

 normal work of the sound-ranging section which was the loca- 

 tion of active enemy batteries. 



Ranging on an objective other than a gun which had just 

 fired was of course subject to the inaccuracies due to wind and 

 temperature. However, in this case the objective was gener- 

 ally a large one such as an ammunition dump, rest billets, cross- 

 roads, or the like, so that a high degree of accuracy was neither 

 sought nor needed. 



