The air driven off in every direction by tremendous and successive concussions came rushing back in shrieking gales, which tore up the waves into blinding foam. For miles in every direction the sea swelled and upheaved into great peaked waves, the repeller rising upon these almost high enough to look down into the awful chasms which her bombs were making. A torpedo-boat caught in one of the returning gales was hurled forward almost on her beam ends until she was under the edge of one of the vast masses of descending water. The flood which, from even the outer limits of this falling-sea, poured upon and into the unlucky vessel nearly swamped her, and when she was swept back by the rushing waves into less stormy waters, her officers and crew leaped into their boats and deserted her. By rare good-fortune their boats were kept afloat in the turbulent sea until they reached the nearest torpedo-vessel. Five minutes afterward a small but carefully aimed motor-bomb struck the nearly swamped vessel, and with the roar of all her own torpedoes she passed into nothing. The British Vice-Admiral had carefully watched the repeller through his glass, and he noticed that simultaneously with the appearance of the cloud in the air produced by the action of the motor-bombs there were two puffs of black smoke from the repeller. These were signals to the crabs to notify them that a motor-gun had been discharged, and thus to provide against accidents in case a bomb should fail to act. One puff signified that a bomb had been discharged to the north; two, that it had gone eastward; and so on. If, therefore, a crab should see a signal of this kind, and perceive no signs of the action of a bomb, it would be careful not to approach the repeller from the quarter indicated. It is true that in case of the failure of a bomb to act, another bomb would be dropped upon the same spot, but the instructions of the War Syndicate provided that every possible precaution should be taken against accidents. Of course the Vice-Admiral did not understand these signals, nor did he know that they were signals, but he knew that they accompanied the discharge of a motor-gun. Once he noticed that there was a short cessation in the hitherto constant succession of water avalanches, and during this lull he had seen two puffs from the repeller, and the destruction, at the same moment, of the deserted torpedo-boat. It was, therefore, plain enough to him that if a motor-bomb could be placed so accurately upon one torpedo-boat, and with such terrible result, other bombs could quite as easily be discharged upon the other torpedo-boats which formed the advanced line of the fleet. When the barrier of storm and cataract again began to stretch itself in front of the repeller, he knew that not only was it impossible for the torpedo-boats to send their missives through this raging turmoil, but that each of these vessels was itself in danger of instantaneous destruction.