but unlike the latter, who moves in comparative safety on terra firma, the former, throughout the length of his flying hours, literally carried his life in his hands, illustrative of which fact may be taken those vivid and realistic sketches penned by Major W. B. Bishop, V.C., who, in his little volume "Winged Warfare," jots down a few impressions of his own breathless experiences. "In the air," for instance, he says, "one did not altogether feel the human side of it. It was not like killing a man so much as just bringing down a bird;" and yet in diving after an enemy machine, "I had forgotten caution and everything else in my wild and overwhelming desire to destroy this thing that for the time being represented all Germany to me." Undeniably the heart of an airman must be "a free and a fetterless thing" to brave the combination of risks incidental to his magnetic calling, and Sir Douglas Haig has not omitted to refer in brief but glowing terms to the "splendid traditions of the British Air Service," the "development of which is a matter of general knowledge," and the combining of whose "operations with those of other arms ... has been the subject of constant study and experiment, giving results of the very highest value." In every direction "much thought had to be bestowed upon determining how new devices could be combined in the best manner with the machinery already working," and in laying stress upon this question of "effective co-operation of the different arms and services," he alludes, for instance, to "increase in the power and range of artillery," which "made the maintenance of communications constantly more difficult." It was in order to assist in the maintenance of a highly efficient system of communications that Crewe was asked to supply quantities of cart cable-drums, the several parts of which required forging, machining, and accurately fitting, and by means of which, when completed as a whole, wires could be run out at a speed of 100 yards per minute; in fact, as Sir Douglas Haig points out, "something of the extent of the constructional work required, in particular to meet the constant changes of the battle-line and the movement of head-quarters, can be gathered from the fact that as many as 6500 miles of cable-wire have been issued in a single week. The average weekly issue of such cable for the whole of 1918 was approximately 3300 miles." Summing up his observations on mechanical contrivances in general, Sir Douglas Haig urges that "immense as the influence of these may be, they cannot by themselves decide a campaign. Their true _rôle_ is that of assisting the infantryman, which they have done in a most admirable manner. They cannot replace him. Only by the rifle and bayonet of the infantryman can the decisive victory be won."