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236 THE CASTLE. at its external base 24 feet, inclusive of the opening. The archway itself is of the remarkable depth of 27 feet 6 inches. Its elevation averages 18 feet. The exterior of the wall is supported by two massive buttresses. The arch is ribbed within by admirably cut stone. Between THE SOUTH GATE FROM WITHOUT THE TOWN WALL. two of these ribs is a vertical aperture of 6 feet 4 inches through the whole breadth of the arch. This aperture creates the appearance of a divided or double arch, one within the other ; and, indeed, there are reasons for supposing that the outer portion of the arch is more
