A nearly square foundation, measuring 18.3 feet by 18.6 feet, with a
narrow extended brick structure protruding from it, was situated some 45
feet north of Wall D, about midway in the wall's length. It was oriented
on a north-northwest--south-southeast axis, quite without reference to
the wall system. The foundation walls and the narrow extension were
exposed by excavation, but the interior area within the walls was not
excavated, except for 2-foot-wide trenches along the edges of the walls.
The foundation itself, about 2 feet thick, consisted of brick
rubble--tumbled and broken bricks, not laid in mortar and for the most
part matching bricks found elsewhere in Marlborough structures.
Scattered among the typical Virginia bricks and brickbats were several
distinctively smaller and harder dark-red bricks measuring 7-1/4 inches
by 3-1/2 inches (fig. 53).
The most interesting feature of the structure was its narrow extension.
This had survived in the form of two parallel walls laid in three brick
courses without mortar, the whole projecting from the southeasterly
wall. The interior measurement between the walls was 1.75 feet and the
exterior overall width was 4 feet. Its southern extremity had an opening
narrowed to 1 foot in width by bricks placed at right angles to the
walls. Approximately 5 feet to the north the passage formed by the walls
was narrowed to 1 foot by three tiers of one brick, each tier laid
parallel to the passage on each side. At 8.7 feet from its southern
terminus the extension intersected the main foundation. Just north of
this intersection, bricks laid within the passage were stepped up to
form a platform two courses high and one course lower than the top of
the foundation. A fluelike opening was formed by two rows of brick laid
on top of the platform, narrowing the passage to a width of 5 inches.
North of the southeast foundation wall there remained a strip of four
bricks in two courses at the level of the opening, forming a thin
continuation of the platform for 3.25 feet.