What is a carronade in the novel, The Wine-dark Sea?

A carronade was a short smoothbore cannon used by the British Navy until about 1860. They were designed as short-range cannons. Light-weight and devoid of many of the features of long guns, carronades were devastating at short ranges but notoriously inaccurate beyond pistol-shot ranges. A carronade weighed approximately one quarter as much as a long gun throwing an equal weight of metal. Aubrey uses carronades as ballast on Surprise, allowing him to transfer them to Franklin to re-arm that ship.