Feet. In. Height of tower from the base to the gallery 63 9 Height of lamp above the gallery 11 0 Total height of the lantern 30 0 Outside diameter at base, over stone moulding 23 0 Outside diameter over cast-iron shell 19 0 Outside diameter just below the cornice 13 11¼ Outside diameter of tower casing at light-room floor 13 8¼ Outside diameter of gallery, to outer ends of brackets 19 10¼ Inside diameter of cellar, or basement story 9 0 Inside diameter of each of the other four stories 12 0 Clear height of cellar 9 0 Clear height of each of the other four stories 12 0 Total thickness of each floor 0 9 The plates composing the cast-iron shell are curved, oblong, rectangular, and 1⅜ inch thick at the base, diminishing gradually to ⅞ inch at the top of the tower. [Illustration: MAPLIN SANDS LIGHTHOUSE.] This lighthouse was erected in 1848, from the design of Mr. Halpin, engineer to the Corporation of Dublin. * * * * * Of lighthouses on piles we shall take as an example the _Maplin Sands Lighthouse_, designed by Mr. Walker, for the Trinity House Corporation, and erected in 1841. It stands upon nine piles of wrought-iron, each 26 feet long and 5 inches in diameter: these are screwed 14 feet 6 inches deep into the sand, and secured by screw-blades of cast-iron, each 4 feet in diameter. One pile forms the centre of an octagon; the others are placed one at each of the eight angles. To the tops of the piles are firmly fitted hollow iron columns; the central one being perpendicular, the others bent, so that they incline inwards. They are braced together by radiating, diagonal, and horizontal rods. Each terminates at the top in a socket, into which is fitted a timber post of about one foot square. The posts, like the columns, are braced together, and form the foundation of the house, platform, and lantern. The principal dimensions are as follows:— Feet. In. Depth of the screw-blades below the sand, about 14 6 Depth of the screw-blades below low-water mark spring-tides 21 0 Rise of spring-tides 15 0 Height from high-water mark spring-tides to floor of house 20 6 Height from high-water mark to floor of light-room 29 6 Height from high-water mark to lamp 38 6 Height from high-water mark to top of vane spindle 54 0 Diameter of floor of house 27 0 Diameter of platform 21 0 Diameter of light-room 12 0