A small metal can punched with holes and filled with oiled rags that were set ablaze when the carcass was shot from a cannon. The purpose, was to cause a ship, a building or a whole town to catch fire.
In artillery, a carcass was a kind of bomb or shell, originally oblong or oval, and later spherical in shape, consisting of an external casing filled with highly flammable matter, and having three to five holes through which the internal flames could blaze outward."Carcass". Oxford English Dictionary. Oxford University Press. 2nd edition. 1989.