Blue Town, the older part of the town, with the dockyard, is defended by strong modern-built fortifications, especially the forts of Garrison Point and Barton's Point, commanding the entrance of both the Thames and the Medway.
Sheerness has some trade in corn and seed,, and there is steamboat connexion with Port Victoria, on the opposite side of the Medway; with Southend, on the opposite side of the Thames; and with Chatham and London, and the town is in some favour as a seaside resort.
Before that time there was no basin or wet-dock, though the river Medway to some extent answered the same purpose, but a portion of the adjoining salt-marshes was then taken in, and three basins have been constructed, communicating with each other by means of large locks, so that ships can pass from the bend of the Medway at Gillingham to that at Upnor.
In the tideway the principal affluents of the Thames are the Brent at Brentford, the Wandle at Wandsworth, the Ravensbourne at Deptford, the Lea at Blackwall, the Darent just below Erith, and the Ingrebourne at Rainham, besides the Medway.
Navigation is also carried on by the Medway to Tonbridge, on the lower parts of the Darent and Cray, from Dartford and Crayford, and on the Wey up to Guildford and Godalming.