 The engines, situated in separate watertight compartments, were each fed by a pair of coal-fired boilers. Each boiler was horizontally mounted and was 9 feet 6 inches (2.90 m) in diameter and 17 feet 6 inches (5.33 m) in length with a total grate area of 220 square inches (1,400 cm2). Yorktown's coal bunkers could carry up to 400 long tons (410 t) of the fuel, and were shielded from "shot and shell". At a near top-speed of 16 knots, the ship could cover 2,800 nautical miles (5,200 km) in 6 ½ days; at the more economical speed of 8 knots (15 km / h) she could cruiser 12,000 nautical miles (22,000 km) over 62 days.
