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 armour
belt and protecting the gun turret, armed with the largest possible guns, which would cost £220,000. The India Office thought that this was too expensive and ordered a repeat of instead for only £132,400. The ships had a
length between perpendiculars of , a
beam of , and a
draught of at
deep load. They displaced . Their crew consisted of 155 officers and men. enough to steam at .
Armament The
Cerberus-class ships mounted a pair of
10-inch rifled muzzle-loading guns in each hand-worked turret. The shell of the gun weighed while the gun itself weighed . The gun had a
muzzle velocity of and was credited with the ability to penetrate a nominal of
wrought iron armour at . The guns could fire both
solid shot and
explosive shells.
Magdala was rearmed in 1892 with four
breech-loading BL 8-inch guns.
Armour The
Cerberus-class ships had a complete
wrought iron waterline belt that was thick amidships and thinned to at the ends. The superstructure and
conning tower were fully armoured, the reason it was called a
breastwork, with of wrought iron. The
gun turrets had on their faces and on the sides and rear. All of the vertical armour was backed by of
teak. The
decks were thick, backed by of teak. ==Service==