Windows and Apertures.—Generally speaking, these are similar in form to the windows in contemporary churches—with this difference, that they never splay, and that the arch-head in numerous examples differs in interior form from that of the exterior. The windows in the earliest towers are square-headed or triangular, and in the latest they are well formed, and of cut stone. The tower was divided into storeys, about 12 feet in height, the floors of which were supported by projections of the masonry or by brackets. Each storey, except the highest, was generally lighted by one small window; the highest has generally four of large size. A conical roof of stone completed the building. The tower usually rested on a low circular plinth; the walls varied in thickness, from 3 to 5 feet; the lowest storey had no aperture, and sometimes its space was filled by solid masonry. The earliest towers were built of rubble masonry; and the spaces between the stones were filled with spawls; little mortar was used in laying the courses, but grouting abundantly. In the latest towers fine ashlar masonry was used, like the Norman work of the twelfth century; a few have external string courses, as in the perfect tower at Ardmore, County Waterford. About seventy round towers still remain, thirteen of which are perfect, of which ten retain the original conical cap.
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Clondalkin Round Tower.
Clondalkin.—In the village of Clondalkin, at a distance of about six miles from Dublin by road, stands one of the best preserved of the round towers. Its height to the top of the cone is 90 feet. The doorway, which is approached by a flight of stone steps, comparatively modern, is square-headed, with inclined sides, and perfectly plain, as are also the windows and top apertures. Some years ago a gentleman of the neighbourhood caused this tower to be repaired, upon which occasion floors were added, and placed in their original position. Access may be had from storey to storey by the aid of fixed ladders, so that a visitor has here an opportunity for observation not frequently to be met with. It should be remarked that the projection at the base, about 13 feet high, and which is nearly all solid masonry, is not found in any other round tower in Ireland, and it may possibly be an afterwork. The tower of Clondalkin, though nearly perfect, cannot be considered a very fine example of its class. It is built of rubble masonry, is somewhat low, and its roof, which does not appear to be original, is wanting in that degree of lightness and elegance observable in many.
The other towers in the immediate neighbourhood of Dublin are at Swords, Lusk, and Rathmichael. That of Swords has been disfigured by the restoration of the top, and the ivy which threatened its destruction has been removed. That of Lusk has been incorporated into the west end of the parish church, and the tower at Rathmichael is a mere stump.
Doorway of Clondalkin Tower.
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Monasterboice.—There is a fine example at Monasterboice, within about six miles of Drogheda. The churches, the tower, and the magnificent crosses of this ancient foundation form a group of ecclesiastical antiquities in some respects unsurpassed in Ireland. A description of the crosses will be found in the previous chapter. The tower, the erection of which there is every reason to refer to an early period, is one of particular interest, exhibiting, as it does, a decorated doorway, the head of which is cut out of two stones laid horizontally one above the other. A band extends round the head and down the sides of the doorway, but terminates on a level with the sill, or rather turns off at a right angle, passing horizontally for a distance of eight inches, from which point it ascends, and running upwards round the doorway head, gives the appearance of a double band. A space between the bands, upon each side of the upper part of the doorway, and one upon the semicircular arched head, left uncut, appear suggestive of the cross. The window immediately over the doorway may be looked upon as a characteristic example of the opening found in a similar position in most of the towers, and which is supposed to have answered the purpose of a second doorway, or to have been designed for the purpose of affording persons within the tower some means of defending the entrance beneath. In this example, however, it is unusually small. The other windows are square-headed, as were also the large apertures of the uppermost storey.[127] The masonry is good, and characteristic of an early period; the stones are large, well fitted together, and pass through a considerable thickness of the wall, as was observed in the injured upper portion of the structure. The tower has been well repaired by the Board of Works, and flights of steps laid from floor to floor, by which the summit of the top storey can be reached.