George Martin
"Barbette tier.--The armament is fully described in the accompanying figure.(*) It consists, in all, of twenty-seven guns, one of which, a 42-pounder, is mounted at the left shoulder angle on a casemate carriage placed on the chassis of a 10-inch columbiad, and a 24-pounder at the left gorge angle is so arranged and the parapet so cut away that it can be depressed to 18o and fired upon the end of the wharf. Several machicoulis galleries of 1 1/2-inch plank (five lined with 1/2-inch iron plate) are placed on the parapet, one on the center of each face and flank, and three on the gorge, over and commanding the main postern; 225 shells, mostly 8-inch, are arranged as grenades, to be rolled off the parapet and exploded by means of a lanyard of proper length. Thunder-barrels are placed at each angle and over the main gate; FRAGMENTS OF STONE, BRICK, &C., ALONG THE BREAST-HEIGHT FOR MISSILES; twenty-three flights of steps lead to the parapet; ammunition in limber-boxes is placed convenient for instant use, and grape, canister, shot, and shell in abundance at each gun. Some five hundred cartridge bags have been made. The powder is well stored in the first-story magazine in the left gorge angle." [Ed Note: emphasis mine]
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"On the esplanade two 8-inch sea-coast howitzers are mounted on casemate carriages only, one each side of the main gate, to sweep the gorge and the approaches to it. The stone &c., has been removed, leaving only a row along the edge to prevent grenades rolling off. Two fougasses, of 12 feet diameter, charged with 50 pounds of powder, are placed against the foot of the scarp wall, one in the center of each half gorge.Two mines, charged with 25 pounds of powder, are sunk in the wharf 40 feet apart."
G. W. SNYDER,
First Lieutenant of Engineers, U. S. Army.
T. SEYMOUR,
Brevet Captain and First Lieutenant, First Artillery
[OR, V. 1, pp. 214-216]
Fougasse is an improvised mine constructed by making a hollow in the ground or rock and filling this with explosives (originally, black powder) and projectiles. Fougasse was well known to military engineers by the mid-eighteenth century but was also referred to by Vauban in the seventeenth century and was used by Zimmerman at Augsburg in the sixteenth century. This technique was used in several European wars, the American Revolution, and the American Civil War. The term is still used in the present day to describe such devices. [From Wikipedia, the free encyclopedia]