more economical inverted vertical compound-expansion steam engines for Reed's original horizontal, low-pressure engines, more powerful guns for the ones first chosen, and the fitting of hydraulic pumps to work the gun turrets. Description Dreadnought had a length between perpendiculars of and was long overall, some longer than the Devastation class. She had a beam of , and a draught of . The ship displaced . Dreadnought was the first ship to have a longitudinal watertight bulkhead that divided the engine and boiler rooms down the centreline. Her crew consisted of 369 officers and ratings. She proved to be a very steady ship with minimal rolling, although she was very wet as high seas usually swept her deck from end to end. The ship was the first large ironclad to have two 3-cylinder inverted vertical compound-expansion steam engines. These were built by Humphry & Tennant and each drove a single four-bladed, propeller. Dreadnoughts engines were powered by a dozen cylindrical boilers with a working pressure of . The engines were designed to produce a total of for a speed of , this was more and faster than the Devastation class. Dreadnought reached a maximum speed of from during her sea trials. The ship carried a maximum of of coal, enough to steam at . Dreadnought was originally intended to be equipped with a pair of RML 12-inch rifled muzzle-loading guns in each turret, but these were replaced by RML 12.5-inch guns while the ship was being redesigned. The shell of the 12.5-inch gun weighed while the gun itself weighed . The shell had a muzzle velocity of and was credited with the ability to penetrate a nominal of wrought iron armour at the muzzle. The gun turrets were rotated by steam power and loaded by hydraulic power. The ship had a complete wrought iron, waterline armour belt that was thick amidships and tapered to outside the armoured citadel towards the ends of the ship. The armour plates were tapered to a thickness of 8 inches at their bottom edge and they extended above the waterline and below it. The armoured citadel protected the bases of the gun turrets, the funnel uptakes and the crew's quarters. The sides of the citadel were thick and it had thick curved ends. The turrets were protected by two plates, each backed by wood. The aft 13-inch bulkhead of the original design was retained, but the