It is a somewhat curious and noteworthy fact, that the Germans were among the first to realise the scope of the airman's activities, and the significance of their relation to the conveyance of intimate information and the direction of artillery fire. Consequently, they now spare no effort to convey illusory information, in the hope that the hostile force may ultimately make a false move which may culminate in disaster. Thus, for instance, as much endeavour is bestowed upon the fashioning of dummy trenches as upon the preparation of the actual lines of defence. And every care will be taken to indicate that the former are strongly held. The dug-outs are complete and at places are apparently cunningly masked. If the airman is flying swiftly, he is likely to fail to distinguish the dummy from the real trenches. To him the defences appear to be far more elaborate and more strongly held than is the actual case. The advantage of this delusion is obvious when a retreat is being made. It enables the enemy to withdraw his forces deliberately and in perfect order, and to assume another and stronger position comparatively at leisure. The difficulty of detecting the dummies is emphasised, inasmuch as now, whenever the sound of an aeroplane is heard, or a glimpse thereof is obtained, the men keep well down and out of sight. Not a sign of movement is observable. For all the airman may know to the contrary, the trenches may be completely empty, whereas, as a matter of fact, they are throbbing with alert infantry, anxious for a struggle with the enemy. This is one instance where the dirigible is superior to the aeroplane. The latter can only keep circling round and round over the suspicious position; the movement through the air interferes with close continuous observation. On the other hand, the dirigible can maintain a stationary position aloft for hours on end. Then the issue is resolved into a contest of patience, with the advantage to the airman. The soldiers in the trenches fret and fume under cover; confined concealment is irksome and is a supreme test of the nerves. Unless the soldiers are made of very stern stuff, physical endurance succumbs. Some rash act--apparently very trivial--may be committed; it suffices for the vigilant sentinel overhead. He detects the slender sign of life, forms his own conclusions, and returns to his headquarters with the intelligence that the enemy is playing "Brer Rabbit."