in separate watertight compartments, were each fed by a pair of coal-fired boilers. Each boiler was horizontally mounted and was in diameter and in length with a total grate area of . Yorktowns coal bunkers could carry up to of the fuel, and were shielded from "shot and shell". At a near top-speed of 16 knots, the ship could cover in 6½ days; at the more economical speed of she could cruiser over 62 days. To supplement her steam power plant, Yorktown was built with three masts that were schooner-rigged. She had a total sail area of . The steam and sail combination was expected to allow Yorktown to remain at sea for months at a time during wartime. Armament Yorktowns main battery consisted of six /30 caliber Mark 3 guns, with each gun weighing in excess of . Two were mounted on the forecastle deck, two on the poop deck, and the other pair amidships on the gun deck. The two guns on the gun deck were mounted above the waterline, while the other four were above. The guns fired armor-piercing projectiles with a propellant charge weighing at . At an elevation of 30.2°, the guns had a range of . Each gun was shielded with steel plating thick. Yorktowns secondary battery consisted of two 6-pounder () guns, two 3-pounder () guns, and two 1-pounder () guns. All were based on designs of the French arms company Hotchkiss. According to a 1902 Bureau of Ordnance publication, an armor-piercing round fired from a 6-pounder gun could penetrate of armor at a distance of . 1889–1897 The ship was commissioned at the League Island (Philadelphia) Navy Yard on 23 April 1889 under the command of Commander French E. Chadwick. After Yorktown conducted her final sea trials, she was assigned to the "Squadron of Evolution"—sometimes also referred to as the "White Squadron"— in late 1889. Yorktown operated with that unit as it developed tactical maneuvers for use by the new steel-hulled naval vessels then coming into service in the United States Navy. After this duty, Yorktown departed the east coast of the United States on 7 December 1889, bound for European waters; stopped briefly at Fayal in the Azores; and arrived at Lisbon, Portugal, two days before Christmas. The ship subsequently cruised the Mediterranean into the early spring of the following year, calling at ports in Spain, Morocco, France, Italy, Greece, and