The question of finding working parties is, however, a minor consideration for the infantry when compared with the possible effects of the explosion of a German mine. This usually occurred either as darkness fell or during the night. Though warning might have been given by the tunnellers that a mine was to be expected, yet the explosion always appeared to come as a surprise. To a man standing up in the vicinity of an explosion the first sensation was a feeling that he had been struck on the soles of the feet by a heavy beam. This was immediately followed by the opening up of the earth and the issuing forth of a belch of flame, capped with a great rolling cloud of smoke and followed instantaneously by a deep muffled roar. Huge fragments of earth and chalk, some weighing a ton or more, with wire entanglements, trench-boards, dug-out timbers--all were hurled many feet into the air. There followed a sensible pause, and then for some seconds the falling débris would come pouring down. This in turn was followed by a mist of dust which continued to float in the air for many minutes. If the explosion had occurred under an occupied portion of the trench, the men in the area which was transferred into the crater were either immediately buried or else hurled many feet into the air in the sheet of flame and smoke, often to descend back into the crater crushed, bruised, burnt, and almost invariably dead. Others in the immediate vicinity of the explosion were crushed in their shelters or buried in the trenches by the collapse of their sides. Men further away, in their turn, were in danger of being killed or mutilated by the falling débris of stones and chalk which whirled down from a great height into the trenches. The result was a scene of horrible desolation. Nothing remained intact. Trenches with their garrisons were obliterated. The positions where posts had once been could only be determined by rifles or limbs projecting through the upturned earth. At times, the heaving of the earth showed where some buried man, still alive, was struggling to extricate himself. The whole air was fetid with the sickly stench of high explosive. Mine warfare was, indeed, the most trying ordeal to which troops holding trenches were exposed. Next to mining, the most nerve-racking form of trench warfare was provided by the trench-mortar. Towards the latter end of August the enemy began to make a considerable use of these weapons. In consequence the trenches were frequently severely damaged, and many casualties were sustained. The British trench-mortars were in these days only in their early experimental stages; moreover, difficulty always existed in obtaining sufficient ammunition for them to be of any real service.