there are many underground excavations in the south of england, also found to some extent in the midlands and the north, but true deneholes are found chiefly in those parts of kent and essex along the lower banks of the thames. with one exception there are no recorded specimens farther east than those of the grays thurrock district, situated in hangman's wood, on the north, and one near challock on the south side of the river south of faversham. isolated specimens have been discovered in various parts of kent and essex, but the most important groups have been found at grays thurrock, in the districts of woolwich, abbey wood and bexley, and at gravesend. those at bexley and grays thurrock are the most valuable still existing. it is generally found that the tool work on the roof or ceiling is rougher than that on the walls, where an upright position could be maintained.