decisive range of its prey, it must be presumed that it isitself also under fire, and all the conditions discussed in the foregoing articles apply. If a machine, type A, has four times the rate of fire of another machine, type B, the machine A, so long as its ammunition holds out, is worth as much as two machines of the type B. In the case of the one-pounder now under discussion, this condition of the exhaustion of the ammunition is just the weak point which renders it doubtful whether under existing circumstances it is worth while seriously to consider the mounting of such a weapon. It is doubtful, also, whether a fully automatic gun of this calibre is admissible with aeroplanes of present-day dimensions, on account of the mean recoil reaction. This is approximately 1 lb, per shot per minute, or at a rate of 100 per minute, 100 lb.; a quantity that would still further hamper the designer in the arrangement of his gun position.
§ 47. The Machine-Gun; Importance of Rapid Fire. For the time being there is no doubt that the ordinary machine-gun is the most serviceable and effective weapon available. Taking, for example, the Lewis gun with its self-contained magazine, the weight of the weapon mounted in place is under 30 lb., and the service ammunition runs 17 to the pound. Assuming, as before, 2½ cwt, as the available total, and taking 4 lb, as the weight of a magazine of 47 rounds, it will be possible to carry some sixty magazines representing nearly 3,000 rounds. The usual manner of employing such a weapon on a moving target, as presented by an aeroplane in flight, is to fire by "bursts," each burst being sighted afresh and commonly consisting of some six or eight shots, so that the speed of fire never averages as high as that of which the gun is capable; thus the supply of ammunition above given would be sufficient for a con-
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