I found one, so here goes. The 1669 structure is Cockham Wood Fort, the remains of which are slowly falling into the Medway between Hoo and Upnor.
The other Fort was Fort Gillingham, a tower like structure which stood at the northern end of the Chatham Lines. Fort Amherst stands at the other end. Fort Gillingham was blown up and the northern end of the Chatham Lines demolished to make way for the construction of the locks and No3 Basin when the Chatham Royal Dockyard was extended between 1868 and 1878.
Both forts were built in response to the Dutch Raid on the Medway in June of 1667.
So, the map shows brickworks on the northern bank of the River Medway between Lower Upnor and Hoo.