100 ANNUAL OF SCIENTIFIC DISCOVERY. 



other, with a more gentle ascent, the two smaller galleries being four 

 feet six inches high, and three feet, six inches broad, and the three being 

 in the form of a capital T. At the farther end of each of the side or 

 cross galleries was a chamber, seven feet cube, lined with wood ; and 

 in each chamber a charge of no less than 12,000 pounds of gunpowder 

 was deposited ; making the distance of the centre of the charge seventy 

 feet from the face of the cliff towards the sea, and about seventy feet 

 above high-water-mark. The galleries were " tamped," that is, stopped 

 up, with bags of sand, and chalk in bags and loose, to within fifty feet 

 of the mouth, both branches being tamped up, and twenty feet down the 

 large gallery. Above this charge of powder, and on the top of the 

 cliff, three shafts were sunk to the depth of forty-one feet, and 600 

 pounds of powder deposited in each. These pits were tamped with 

 chalk. 180 feet from the edge of the cliff, a small wooden house was 

 erected, in which were placed three voltaic batteries, two of Groves's 

 and one of Smee's, for firing the charges. Extending from each de- 

 posit of powcler, and connecting with the batteries, wires, covered 

 with tape and varnished, were deposited, for the purpose of conveying 

 the electric spark ; the wires for the two lower charges being carried 

 over the top of the cliff. It was arranged that the two great charges 

 should be fired simultaneously, and the others a few moments after- 

 wards. 



A correspondent of the London Times gives the following descrip- 

 tion of the explosion: "As the appointed hour drew near, every 

 eye was fixed upon the place where the explosion was to be, marked 

 out as it was by a flag upon its highest point. It was not till twelve 

 minutes past three o'clock, that suddenly the whole cliff, along a width 

 or frontage of some 120 feet, bent towards the sea, cracked in every 

 direction, crumbled into pieces, and fell upon the beach in front of it, 

 forming a bank, down which large portions of the falling mass glided 

 slowly into the sea for several yards, like a stream of lava flowing into 

 the water. There was no very loud report ; the rumbling noise was 

 probably not heard a mile off, and was perhaps caused by the split- 

 ting of the cliff and fall of the fragments. There seemed to be no 

 smoke, but there was a tremendous shower of dust. Those who were 

 in boats a little \vay out state that they felt a slight shock. It was 

 much stronger on the top of the cliff. Persons standing there felt 

 staggered by the shaking of the ground, and one of the batteries was 

 thrown down by it. In Seaford, too, three quarters of a mile off, 

 glasses upon the table were shaken, and one chimney fell. The mass 

 which came down is larger than was expected ; it forms an irregular 

 heap, apparently about 300 feet broad, of a height varying from 40 to 

 100 feet, and extending 200 or 250 feet more seaward, which is con- 

 siderably beyond low-water-mark." The effect produced was caused 

 entirely by the two great charges in the lower chambers, as the wires 

 to the pits on the top of the cliff became disrupted by the explosion 

 below, before a current could be passed through them to the powder 

 at their termination. The execution of this work was performed 

 under the direction of the Board of Ordnance, by a corps of 55 men 

 belonging to the Sappers and Miners. The time occupied was about 

 seven weeks. 



