Caiˊsson [Gunnery]

a wooden chest, containing 4 or 6 Bombs; or filled only with Powder, which the Besieged bury under Ground, in order to blow up a Work that the Besiegers are like to be Masters of. Thus after the Bonnet has been blown up by the Mine, they lodge a caisson under the Ruins of it, and when the Enemy has made a Lodgement there, they fire the caisson by the help of a saucis, and blow up that Post a second time.