HEAD lam: developments in artillery 315 



chance of killing a German. To enable it to be done the topo- 

 graphical sections provide batteries with maps, mounted so as to 

 avoid errors due to shrinkage or warping, and showing accurately 

 not only the positions of the guns and observing stations, but also 

 such datum points as may be desired in the enemy's lines. 



Error of the day. Having by this means found the errors of the 

 guns, a battery commander has next to think of the error of the 

 day, or rather of the moment. He must ascertain and allow for 

 the height of the barometer, the temperature of the air, the tem- 

 perature of the charge, and the force and direction of the wind 

 for a* given time of flight, and here he has to depend on his scien- 

 tific friend "Meteor" who sends to him every few hours cryptic 

 telegrams. 



Error of the gun. And yet after all this meticulous care, we have 

 to recognize that a series of rounds fired at the same elevation will 

 not fall on the same spot, but will cover a rectangle varying in size 

 with the gun and the range. The size of the ' '50 per cent zone" — 

 the length and breadth of which are a quarter of those of the 100 

 per cent zone — is given in the range table of each gun, and this 

 has to be continually in the mind of the battery commander, for 

 without a thorough realization of it he can not judge how many 

 rounds will be required to accomplish such a task as, for instance, 

 the destruction of an enemy's battery. But its most important 

 use is perhaps to avoid danger of shelling one's own troops. 

 Nothing is so distressing to an artillery general as to receive com- 

 plaints from the infantry that his shells are falling in their trenches, 

 and yet whatever the skill of his batteries this must happen some- 

 times, with the lines as close together as they are, unless this in- 

 herent quality in the gun is recognized and allowed for. 



Difficulty of applying calculations in the field. ' I will not pursue 

 the subject further, but remember that though the calculations 

 may appear very simple to you, they are not so easy, given the 

 conditions under which they have to be made — the absence of any 

 conveniences, the presence of every disturbing element. It is very 

 easy then to make an error which may have fatal results. One of 

 my best battery commanders was killed by a shell from his own 

 battery when himself conducting the fire from a trench from which 

 he had cleared the infantry. 



