Serving as coxswain on board the USS Carondelet, Morrison was commended for meritorious conduct in general and especially for his heroic conduct and his inspiring example to the crew in the engagement with the rebel ram Arkansas, Yazoo River, 15 July 1862. When the Carondelet was badly cut up, several of her crew killed, many wounded and others almost suffocated from the effects of escaped steam, Morrison was the leader when boarders were called on deck, and the first to return to the guns and give the ram a broadside as she passed. His presence of mind in time of battle or trial is reported as always conspicuous and encouraging.