Although the general plan of Harlech is evidently the work of one mind and its execution generally of one date, there are some appearances in the work which show that alterations and additions were introduced affecting, not the general plan, but certain of its parts. It is evident that parts of the curtain have been thickened about 2 feet,—the north and south walls by additions inside; the west, on the outside. Also this thickening seems to have been decided upon when the walls were 30 feet high, as above that level they are of one mass and date. The exterior stair on the inner face of the great gatehouse was also an afterthought, and the doorway at its head clearly was not originally introduced. Besides this, the six windows on that front of the gatehouse, in the two upper floors, have been reduced in height by the insertion of a segmental arch between 2 feet and 3 feet below the original head; but the pattern is the same, and the masonry filling up the space seems of the date of the window, or very nearly so. These windows are of a peculiar pattern. Their two lights are trefoiled; and in the spandrels are also trefoils pierced. The mouldings are concave; and one is a small hollow, as in the early Perpendicular style. They must, however, be original. The inference from these alterations seems to be, that Edward visited the castle when the works were far advanced, and the hall, gatehouse, and the lower part of the north, south, and west curtains built. The gatehouse curtain was probably always intended to be of its present height, as at Caerphilly. He ordered the other three curtains to be thickened and raised to the full height of the gatehouse curtain; to obey which order, the thickening was applied where possible on the inside, but where the hall prevented this, on the outside. The upper part of the walls so raised would, of course, be of one date, and solid. At the same time it was decided to make the rooms of the upper floors of the gatehouse those of state; and as the ways up the well-staircases were not thought suitable, a new and more direct staircase was built and a new door opened in the wall. The chapel in the inner ward seems a still later addition. The character of the masonry throughout is exceedingly rough, as though hastily executed. It is rubble, and some of it very poor rubble indeed. The towers are of far better work than the curtains. The stones are larger, and their interstices filled in with more care. The ashlar is very good, but is sparingly used, and confined to the dressings, window-cases, chimney-hoods and heads, and a few of the more important doorways. The ordinary doors are mere openings to the walls, without rebates or chamfer, with shouldered heads of a rude character; and the sewer-openings, seen under the garderobes, have merely long stones for lintels. The masonry of the covered way and water-gates is also very inferior, and much of the side wall has, in consequence, slipped away from the rock.