Spithead Forts
1863 At Spithead the distance of the shore-line on either side of the channel leading to Portsmouth was seen to be too great to allow batteries on the mainland to prevent the entrance of ships. Therefore two circular granite forts would be sited on two shoals at the entrance to the channel. Each of these forts would have 90 guns, the two lower tiers of guns were to be in casemates, the upper in embrasures made of iron, covered in partly from above.