Very remarkable in this castle are the subterranean galleries, driven in the chalk rock beneath the lines of the original wall, and behind the scarp of the ditch. These are now in part blocked up, but there still remain two or three hundred yards of them of which the direction is known. They are entered by a passage in the inner ward, in its north-west quarter, and by a descent of fifty-four steps near the keep, and possibly from other points now lost. The galleries are about 7 feet high and 6 feet wide, rudely cut, and somewhat singularly laid out. They lie within, without, and beneath the wall, and give off frequent spurs or short passages intended to occupy any space in which a mine was likely to be opened. At this time they have been broken into at three or four points in the scarp of the ditch, about half-way down. They were intended as a system of permanent counter mines to meet any attempt at mining on the part of the besiegers. In one place a large central pier is surrounded by a gallery, whence the branches go off,—an arrangement intended probably to check the progress of those who might break in. So far as is known, these galleries, of which a survey was made in 1708, are confined to the southern half, or four-fifths of the old castle. There are none under the outer ward. Outside, and to the north-east of the outer gate, are some semicircular platforms, which seem to have played a part in the defence of the castle; but whether before or after the use of artillery is uncertain. The Bel.—A curtain wall, which originally was about 5 feet thick, and from 15 feet to 20 feet high, commences abruptly upon the crest of the counterscarp in two places; one on the east opposite to the mural tower, which marks about the centre of that front of the castle, and thence descends towards the river; and the other north, close outside of the drawbridge of the main entrance. This latter wall is continued down the hill, and makes a bold sweep towards the town, and, finally reaching the river bank, joins the river wall. The enclosure thus formed contains about twice the area included by the ditch of the castle, and has long been known as Le Bel or La Baile, a form evidently of the Norman-Latin _Ballium_, called by us the “Bailey.” This enclosure is traversed by the road from Dieppe to Martigny, which passes through the two gates bearing those names. A third, or water-gate to the east, opened upon the river. Upon the north front appear to have been two small half-round mural towers, of which one remains. The river has somewhat encroached upon the lower part of the Bel, and has undermined part of the wall.