 He was promoted to First Assistant Engineer in 1858, and was ordered to the USS "Niagara", which made a round-trip voyage late that year to Monrovia, Liberia, transporting slaves liberated in August when a slave ship was captured off Cuba by another U.S. warship.Just prior to Robie's arrival on the ship, the "Niagara" had participated in the second attempt, this time successful, to lay the Transatlantic telegraph cable.His next assignment was as First Assistant Engineer aboard the steam sloop USS "Lancaster".