 The sloped armoured deck ranged in thickness from 2 @.@ 5 to 4 inches ( 64 to 102 mm ) on the flat and slopes , respectively . The casemates were protected by 6 inches of Harvey armour while the gun shields had 2 to 4 @.@ 5 inches ( 51 to 114 mm ) of armour . The conning towers were protected by 12 @-@ inch ( 305 mm ) walls and their roofs were 2 inches thick . The tubes protecting the ammunition hoists were also 2 inches thick . 
