Support for the expedition had been arranged by Francis Beaufort, hydrographer of the Navy and a member of several scientific societies. On the expedition was Joseph Dalton Hooker, who had been invited along as assistant surgeon. Erebus and Terror were bomb vessels – an unusual type of warship named after the mortar bombs they were designed to fire and constructed with extremely strong hulls, to withstand the recoil of the mortars, which were to prove of great value in thick ice.