The two experiments are particularly interesting, as showing how closely the results agree, although the conditions are dissimilar in one respect: viz. that in the first case the number of rounds was unlimited and the result had to be obtained within one minute; while in the second case time was unlimited, but the number of rounds fired by each was the same. The result of the two experiments show that both in accuracy and rapidity a machine gun is much superior to 42 picked shots, whether firing the same number of rounds at known ranges or firing an unlimited number of shots in a given time at an unknown range. We shall not be wrong, then, if we say that a machine gun is at least equal to 50 rifles in fire value,[2] but there are other factors to be considered as well as fire effect in determining its tactical value, and it is in these other factors that machine guns are so far superior to riflemen as to make a reliable estimate of their relative value almost impossible; these factors are: (1) Mobility; (2) Visibility; (3) Vulnerability. _Mobility._--The mobility of the infantry soldier is limited to the rate at which he can march, which on the battlefield is about 100 yards a minute or less than three-and-a-half miles an hour. Doubling may be left out of the question, as it quickly reduces fire efficiency to a minimum. An experiment made in the Austrian Army showed that the percentage of hits which was 76·5 per cent. after an advance in quick time, fell to 51 per cent. after doubling.[3] The mobility of the machine gun will depend almost entirely on the way it is carried, and must not be judged by any particular carriage which may happen to be in use for the time being in our own service. A short description of these mountings and their method of transport will be found in Chapter IX., but none of them are entirely satisfactory. The infantry carriages are heavy, clumsy, and conspicuous, and are the least mobile of all; they can hardly be moved out of a walk without risk, and Marks III. and IV. cannot come into action without first unharnessing the mule or horse, and they then have to be dragged into position by the whole detachment--thus presenting a most conspicuous and vulnerable target at the moment when least desired and when concealment and invisibility are essential to tactical success.[4] In the German Official Account of the late Boer War, issued by the General Staff, is the following criticism of this carriage: “Both sides have machine guns, but the rather clumsy mountings of those used by the British offered too high a target, and so prevented their being advanced from position to position during the attack.” The tripod mounting, which is light and inconspicuous, is carried with the gun on a limbered wagon; but the advantages of its lightness and portability are almost neutralised by being carried on a wagon, thus reducing its mobility by confining it to ground suitable for wheeled vehicles.