Page:Southern Historical Society Papers volume 05.pdf/153

148 the lower cable, and the buoys or floats to the upper one. The upper cable carried a fringe of smaller ropes, about three-fourths of an inch in diameter by fifty feet long, which floated as so many "streamers" on the surface, destined to foul the screw propeller of any steamer which might attempt to pass over the obstruction. Shortly after these cables were in position a blockade-runner, in attempting at night to pass through the gap purposely left open near the Sullivan Island shore, under the guns of Fort Moultrie and of the outside batteries, accidentally crossed the end of the rope obstruction, when one of the streamers got entangled around the shaft, checking its revolutions. The vessel was at once compelled to drop anchor to avoid drifting on the torpedoes or ashore, and afterward had to be docked for the removal of the streamer before she could again use her propeller. The torpedoes, as anchored, floated a few feet below the surface of the water at low tide, and were loaded with one hundred pounds of powder arranged to explode by concussion—the automatic fuse employed being the invention of Capt. Francis D. Lee, an intelligent young engineer officer of my general staff, and now a prominent architect in St. Louis. The fuse or firing apparatus consisted of a cylindrical lead tube with a hemispherical head, the metal in the head being thinner than at the sides. The tube was open at the lower extremity, where it was surrounded by a flange; and, when in place, it was protected against leakage by means of brass couplings and rubber washers. It was charged as follows: In its centre was a glass tube filled with sulphuric acid and hermetricallyhermetically [sic] sealed. This was guarded by another glass tube sealed in like manner, and both were retained in position by means of a peculiar pin at the open end of the leaden tube; the space between the latter and the glass tube was then filled with a composition of chlorate of potassa and powdered loaf sugar, with a quantity of rifle powder. The lower part of the tube was then closed with a piece of oiled paper. Great care had to be taken to ascertain that the leaden tube was perfectly water-tight under considerable pressure. The torpedo also had to undergo the most careful test. The firing of the tube was produced by bringing the thin head in contact with a hard object, as the side of a vessel; the indentation of the lead broke the glass tubes, which discharged the acid on the composition, firing it, and thereby igniting the charge in the torpedo. The charges used