in ruins. Its site by the shoreline has since been eroded away by tidal action, though it is possible that remains from the blockhouse may still survive under the river mud. Coalhouse Battery The June 1687 Raid on the Medway by the Dutch fleet during the Second Anglo-Dutch War exposed the weaknesses of the Thames defences. It took another hundred years for the defences on Gravesend Reach to be improved, in the form of new works at Gravesend and Tilbury built in the 1780s, but even then the potential of forward defence – to prevent enemies accessing the lower Thames – continued to be neglected. It was not until the outbreak of the French Revolutionary Wars that the need for effective forward defence was addressed. Lieutenant Colonel Hartcup of the Royal Engineers carried out a survey of the Thames in 1794 in which he recommended building a triangle of artillery batteries to guard the entrance to Gravesend Reach and the next reach of the river, Lower Hope Reach. Two of the batteries would be located on the south bank at Shornemead, about north-west of Higham; at Lower Hope Point, about north-west of Cliffe; and on the north bank at East Tilbury, about north of the old Henrician blockhouse. The batteries would have a maximum range of about and their arcs of fire would overlap, enabling them to support each other. The new battery was constructed during 1799 on marshy ground a short distance south-east of St Catherine's Church. It took its name from the nearby Coalhouse Point, which was named for a coal wharf that once existed there to serve East Tilbury. The soft soil caused many problems but the work was completed by July of that year. It was equipped with four 24-pounder (pdr.) cannon mounted on traversing carriages, which enabled the gunners to track targets much more easily than had been the case with traditional garrison carriages. The battery faced the river with a semi-circular earthen rampart on which the guns were mounted. A walled-off area to the rear enclosed a barracks, magazine and shot kiln (for heating shot to set wooden ships on fire). The whole structure was surrounded by a polygonal water-filled ditch. It was modified in 1810 to raise the height of the rampart and to add a small expense magazine where ammunition was stored for immediate use. The French did not test the Thames