It has two tiers of casemates, besides a heavy barbette battery.
"Three Months in the Southern States, April-June 1863"
Arthur J. L. (Lieut.-Col.) Fremantle
He told me that Fort Sumter was to be covered by degrees with the long green moss which in this country hangs down from the trees: he thinks that when this is pressed it will deaden the effect of the shot without being inflammable; and he also said that, even if the walls of Fort Sumter were battered down, the barbette battery would still remain, supported on the piers.
"Three Months in the Southern States, April-June 1863"
Arthur J. L. (Lieut.-Col.) Fremantle
The after barbette swung round, and at the same moment, or perhaps half a minute before, Erskine touched two other buttons in rapid succession.
"The World Peril of 1910"
George Griffith