In 1838, he received command of the second-class ship sloop and headed to the Mediterranean to again serve under Hull. A principal ancillary duty involved educating and training young midshipman. Percival undertook the task with zeal and passion. Prominent men and fellow officers with midshipmen sons commonly asked for their youngster to be placed under the stern tutelage of Mad Jack. The young men did not always appreciate it at the time, but many went on to notable careers. As one example, Gustavus V. Fox chafed under Percival's disciplined approach on the cruise, but went on to become Lincoln's assistant secretary of the navy. Others distinguished themselves in combat. John L. Worden, a "Cyane" midshipman, became an admiral and is remembered as a hero of the Battle of Hampton Roads. One of the most irksome midshipmen on the cruise, nonetheless, recognized an appreciated their skipper. Henry A. Wise summarized the almost universal feeling in the service when he noted: "There is not a better sailor in the world than Cap. Percival or a man of better judgement in the qualities requisite for a Seaman. ... One would suppose from his impatient & passionate temper, that in case of danger he would lose all command of himself. On the contrary no one is cooler or more able to fulfill the duties of his station. To give the devil his due—I would rather trust my life to his charge in case of emergency at Sea than any other man in the United States Navy."