The lighthouse is itself an object of great interest and beauty, and is constructed according to the most approved models of modern times. Its form is that of a frustrated cone, supporting a lantern which exhibits a fixed bright light. The illumination, according to the system now generally adopted by the Trinity-house, is produced by a set of reflectors ground to the parabolic form, in the foci of which twenty large oil lamps are placed: an outer gallery, lightly but securely railed, surrounds the dome. Connected with the building on its east side, there is a large room, which opens by folding doors on a platform, and where an excellent telescope is kept, by means of which the shoals which obstruct the entrance to the bay may be distinctly observed--namely, the great Kish, and the Bennet and Burford banks, which are links of the chain extending along the Wicklow and Wexford coasts, and called the Irish grounds. These, though not visible, are distinctly marked in stormy weather by the surf, which breaks over them with uncommon violence, and form a dangerous obstruction to the approach to the bay. The Baily lighthouse was erected by the Ballast Board of Dublin in 1814, previous to which time the Howth light, as it was commonly called, stood on a hill considerably more to the north, and at an elevation of more than three hundred feet above sea level. This circumstance of its great elevation, led, however, to its being abandoned, and the erection of the Baily lighthouse in its place, as it was found to be frequently involved in clouds and mist, while lower stations were clear and well defined. The Baily lighthouse is a spot of no less antiquarian than picturesque interest. Its name, which is cognate with the Latin _ballium_, is derived from an ancient circular stone fortress which encircled the apex of the rock, and of which considerable remains existed previous to the erection of the present buildings. This great keep was fortified by three earthen walls, with deep intervening ditches placed at the entrance to the narrow peninsula, and by extending from one side of it to the other, cut it off completely from the promontory. These works still remain, though in a very ruinous state; yet they are sufficiently distinct to mark their purpose, and to convey a good idea of the style of military defensive works in use in extremely remote times. They will be found marked on the Ordnance map.