ten o'clock
There she lay to against a strong breeze from the east . It was not yet ten o'clock when the officer in charge of the starboard gun remarked to the director that he suppose that it would not be necessary to give the smoke signals , as had been done in the channel , as now all the crabs were lying near them . The director reflected a moment , and then ordered that the signals should be given at every discharge of the gun , and that the columns of black smoke should be shot up to their greatest height . At precisely ten o'clock , up rose from Repeller No . 11 two tall jets of black smoke . Up rose from the promontory of Caerdaff , a heavy gray cloud , like an immense balloon , and then the people on the hill-tops and highlands felt a sharp shock of the ground and rocks beneath them , and heard the sound of a terrible but momentary grinding crush . As the cloud began to settle , it was borne out to sea by the wind , and then it was revealed that the fortifications of Caerdaff had disappeared .