 Unlike her half @-@ sisters , Northumberland was armed with a mix of seven @-@ inch ( 178 mm ) , eight @-@ inch ( 203 mm ) , and nine @-@ inch ( 229 mm ) rifled muzzle @-@ loading guns . All 4 nine @-@ inch and 18 eight @-@ inch were mounted on the main deck while 4 eight @-@ inch guns were fitted on the upper deck as chase guns . Both seven @-@ inch guns were mounted in the stern on the main deck , also as chase guns . 
