In July 1866 the India Office asked for two floating batteries to defend Bombay and the Controller of the Navy, Vice Admiral Spencer Robinson recommended that monitors be used. He recommended a design with 12inches armour belt and 15inches protecting the gun turret, armed with the largest possible guns, which would cost £220,000.[2] The India Office thought that this was too expensive and ordered a repeat of instead for only £132,400.[3]
The ships had a length between perpendiculars of 225feet, a beam of 45feet, and a draught of 15inchesft3inchesin (ftin) at deep load. They displaced 3340LT. Their crew consisted of 155 officers and men.
Magdala had two horizontal direct-acting steam engines, made by Ravenhill, each driving a single propeller. The ship's boilers had a working pressure of 30psi. The engines produced a total of 1369ihp on 21 October 1870 during the ship's sea trials which gave her a maximum speed of 10.67kn. Magdala carried 220LT of coal,[4] enough to steam 450nmi at 10knots.[5]
The Cerberus-class ships mounted a pair of 10-inch rifled muzzle-loading guns in each hand-worked turret. The shell of the 10adj=onNaNadj=on gun weighed 407lb while the gun itself weighed 18LT. The gun had a muzzle velocity of 1365ft/s and was credited with the ability to penetrate a nominal of wrought iron armour at 100yd. The guns could fire both solid shot and explosive shells.[6] Magdala was rearmed in 1892 with four breech-loading BL 8-inch guns.[7]
The Cerberus-class ships had a complete wrought iron waterline belt that was 8inches thick amidships and thinned to 6inches at the ends. The superstructure and conning tower were fully armoured, the reason it was called a breastwork, with 8- of wrought iron. The gun turrets had 10inches on their faces and 9inches on the sides and rear. All of the vertical armour was backed by 9inches-11inchesin (-in) of teak. The decks were 1.5inches thick, backed by 10inches of teak.[8]
HMS Magdala was laid down on 6 October 1868 by the Thames Ironworks in Leamouth, London. She was launched on 2 March 1870 and completed in November 1870. For her delivery voyage to India, Magdala was fitted with three temporary masts and made the trip under sail in the middle of winter without escort, as both her builders and the Royal Navy, considered her sufficiently seaworthy as to make the trip safely. Her life thereafter was wholly spent in Bombay Harbour, with occasional short trips to sea for firing practice.[9] She was sold for scrap in January 1903.[10]
. George Alexander Ballard . The Black Battlefleet . 1980 . Naval Institute Press . Annapolis, Maryland. 0-87021-924-3.