▁added , ▁with ▁only ▁spl inter ▁protection : ▁ ▁thick ▁sides ▁and ▁a ▁ ▁thick ▁roof . ▁The ▁bar b ettes ▁for ▁the ▁main ▁battery ▁guns ▁had ▁ 2 5 4   mm ▁of ▁wr ought ▁iron ▁back ed ▁with ▁ 2 5 0   mm ▁of ▁te ak . ▁ ▁Mod ifications ▁After ▁ 1 8 8 6 , ▁three ▁ ▁tor ped o ▁tub es ▁were ▁installed ▁on ▁each ▁ship ; ▁one ▁t ube ▁was ▁placed ▁in ▁a ▁sw ivel ▁mount ▁in ▁the ▁stern ▁and ▁two ▁were ▁placed ▁in ▁the ▁bow , ▁sub mer ged . ▁The ▁tub es ▁were ▁supplied ▁with ▁a ▁total ▁of ▁ 1 2 ▁tor ped o es . ▁Later , ▁a ▁pair ▁of ▁ ▁tor ped o ▁tub es ▁were ▁mounted ▁in ▁the ▁ships ' ▁h ull s ▁above ▁water ▁on ▁the ▁broad side . ▁ ▁The ▁ships ▁were ▁more ▁heavily ▁re built ▁in ▁the ▁late ▁ 1 8 9 0 s ; ▁their ▁engines ▁were ▁replaced ▁and ▁the ▁bo ilers ▁were ▁du cted ▁into ▁a ▁single ▁large ▁fun nel . ▁These ▁improvements ▁increased ▁the ▁spe eds ▁of ▁the ▁ships ▁to ▁. ▁The ▁battery ▁of ▁ 8 . 7   mm ▁guns ▁was ▁replaced ▁with ▁an ▁equal ▁number ▁of ▁ ▁SK ▁L / 3 0 ▁guns ▁and ▁four ▁ ▁guns . ▁Each ▁ship ▁also ▁had ▁their ▁old ▁wr ought ▁iron ▁arm or ▁and ▁te ak ▁backing ▁replaced ▁with ▁new ▁Kru pp ▁arm or ▁that ▁significantly ▁increased ▁their ▁ability ▁to ▁with stand ▁shell ▁hits . ▁ ▁Const