galleries were tamped with sand and chalk, in bags, to within fifty feet of the mouth, both branches being tamped up, and twenty feet down the large gallery. “The men worked in reliefs for the whole twenty-four hours. For the gallery three reliefs of four men each, were appointed; and subsequently for the branches three reliefs of six men for the two.... The relieving hours were 6 A.M., 6 P.M., and midnight, except at periods when the high spring tides prevented the relief passing a projecting part of the cliff at the proper hours, when arrangements were made to equalize the extra time the men were so employed.... The work was hardly ever interrupted in its progress, for by compelling each relief to be in barracks six hours before their turn came for work, the men were invariably fresh at the commencement of their time; and as the working pay was good and the best miners were always employed, the average amount of work performed by night equalled that accomplished by day.” All the necessary operations being completed, the great explosion, on a signal from the galvanic battery by sergeant Edward Wright took place on the 19th September, under the immediate orders of Colonel Lewis. The effect of firing the two great chambers was to throw out the under portions of the rock, which, from the downward pressure of the superincumbent masses, rolled with a convulsive heaving towards the sea, carrying with them the three smaller chambers unexploded, and causing deep fissures in the chalk as far back as the very foundation of the battery shed. The undertaking, so far as dislocating an immense mass of chalk from the cliff was concerned, was thus perfectly successful; but subsequent experience has thrown doubts upon its utility as a breakwater, for the chalk is gradually being washed away, and if some natural intervention does not take place to conglomerate the mass into a compact resisting body, time will remove the headland altogether, and expose as before the land and its defences to the gradual invasion of the sea. The explosion was one of the largest that had ever occurred, and passed off without accident, delay, confusion, or inconvenience to any one of the detachment engaged, or to the thousands of spectators who witnessed the operation.[48] The quantity of chalk displaced was about 200,000 cubic yards, or about 292,000 tons. The distance the debris was hurled in front of the original line of cliff was more than 300 feet. The average breadth of the mound formed was about 360 feet, and its mean height about 50 feet.