HMS Black Prince ( 1861 ) HMS " Black Prince " was the third ship of that name to serve with the Royal Navy . She was the world ' s second ocean - going , iron - hulled , armoured warship , following her sister ship , . For a brief period the two s were the most powerful warships in the world , being virtually impregnable to the naval guns of the time . Rapid advances in naval technology left " Black Prince " and her sister obsolete within a short time , however , and she spent more time in reserve and training roles than in first - line service . " Black Prince " spent her active career with the Channel Fleet and was hulked in 1896 , becoming a harbour training ship in Queenstown , Ireland . She was renamed " Emerald " in 1903 and then " Impregnable III " in 1910 when she was assigned to the training establishment in Plymouth . The ship was sold for scrap in 1923 . Design and description . HMS " Black Prince " was long between perpendiculars and long overall . She had a beam of and a draught of . The ship displaced . The hull was subdivided by watertight transverse bulkheads into 92 compartments and had a double bottom underneath the engine and boiler rooms . Propulsion . The " Warrior " - class ships had one 2 - cylinder trunk steam engine made by John Penn and Sons driving a single propeller . Ten rectangular boilers provided steam to the engine at a working pressure of . The engine produced a total of during " Black Prince " s sea trials in September 1862 and the ship had a maximum speed of under steam alone . The ship carried of coal , enough to steam at . The ironclads were ship rigged and had a sail area of . " Black Prince " could only do under sail , slower than her sister . Armament . The armament of the " Warrior " - class ships was intended to be 40 smoothbore , muzzle - loading 68 - pounder gun s , 19 on each side on the main deck and one each fore and aft as chase gun s on the upper deck . This was modified during construction to ten rifled 110 - pounder breech - loading guns , twenty - six 68 - pounders , and four rifled breech - loading 40 - pounder guns . The solid shot of the 68 - pounder gun weighed approximately while the gun itself weighed . The gun had a muzzle velocity of and had a range of at an elevation of 12° . The shell of the 110 - pounder Armstrong breech - loader weighed . It had a muzzle velocity of and , at an elevation of 11 . 25° , a maximum range of . The shell of the 40 - pounder breech - loading gun was in diameter and weighed . The gun had a maximum range of at a muzzle velocity of . In 1863 – 64 the 40 - pounder guns were replaced by a heavier version with the same ballistics . All of the guns could fire both solid shot and explosive shells . " Black Prince " was rearmed during her 1867 – 68 refit with twenty - four 7 - inch and four rifled muzzle - loading guns . The ship also received four 20 - pounder breech - loading guns for use as saluting guns . The shell of the 15 - calibre 8 - inch gun weighed while the gun itself weighed . It had a muzzle velocity of and was credited with the ability to penetrate a nominal of wrought iron armour at the muzzle . The 16 - calibre 7 - inch gun weighed and fired a shell . It was credited with the nominal ability to penetrate armour . Armour . The sides of " Black Prince " were protected by an armour belt of wrought iron , thick , that covered the middle of the ship . The ends of the ship were left entirely unprotected which meant that the steering gear was very vulnerable . The armour extended above the waterline and below it . 4 . 5 - inch transverse bulkheads protected the guns on the main deck . The armour was backed by of teak . Service . " Black Prince " was ordered on 6 October 1859 from Robert Napier & Sons in Govan , Glasgow for the price of £377 , 954 . The ship was laid down on 12 October 1859 and launched 27 February 1861 . Her completion was delayed by a drydock accident at Greenock while fitting out , which damaged her masts . She steamed to Spithead in November 1861 with only jury - rigged fore and mizzenmasts . The ship was commissioned in June 1862 , but was not completed until 12 September 1862 . " Black Prince " was assigned to the Channel Fleet until 1866 , then spent a year as flagship on the Irish coast . Overhauled and rearmed in 1867 – 68 , she became guardship on the River Clyde . The routine of that duty was interrupted in 1869 when she and " Warrior " towed a large floating drydock from Madeira to Bermuda . " Black Prince " was again refitted in 1874 – 75 , gaining a poop deck , and rejoined the Channel Fleet as flagship of Rear Admiral Sir John Dalrymple - Hay , second - in - command of the fleet . In 1878 Captain H . R . H . Duke of Edinburgh took command and the ship crossed the Atlantic to participate in the installation of a new Governor General of Canada . Upon her return " Black Prince " was placed in reserve at Devonport , and , reclassified as an armoured cruiser , she was reactivated periodically to take part in annual fleet exercises . " Black Prince " was hulked in 1896 as a harbour training ship , stationed at Queenstown , and was renamed " Emerald " in 1903 . In 1910 the ship was moved to Plymouth and renamed " Impregnable III " when she was assigned to the training school HMS " Impregnable " before she was sold for scrap on 21 February 1923 .