The foundation upon which this enormous mass of material rests, is necessarily very strong, and consists, in the first place, of a ring of concrete, sixty feet in external diameter, and three feet deep; upon this is built a circular wall of brick-work, laid in cement, fifty-six feet in diameter, and eighteen feet deep. This forms the bed on which rests the base pieces of the columns. The columns, 1 foot in diameter, and 24 in number, are placed in pairs, 4 feet apart, and are connected together by solid vertical girders or filling-in frames, each pair thus forming one continuous broad column, extending from the base to the bottom of the tank by which the tower is surmounted; the whole rising to a height of 202 feet. The space between each pair of columns (8 feet) is filled in with glazed sashes and face-work, corresponding with those in the building, and completing the shell of the tower. Behind these sashes, and spanning these spaces, extending from floor to floor, are series of round wrought-iron diagonal bracing, continued from the bottom to the top of the tower; and, under each of the ten landing-floors, is a strong horizontal bracing-plate, termed a diaphragm, forming, with the diagonal bracing above referred to, a system of vertical and horizontal trussing. Up the centre of each tower is carried a perpendicular brick shaft (the internal diameter of which is 7 ft. 9 in.), resting upon a separate foundation, and serving the double purpose of carrying off the smoke from the heating apparatus, from the boilers connected with the Machinery Department, the upper engine-house, and kitchen, and forming the core or spiral staircase by which the various floors, and gallery at the top of the tower, are reached. These floors arise at intervals of twenty feet from the level of the floor of the main building. The tank noticed above is of boiler-plate, and is formed of an inner and outer wall, the former of which encircles the chimney-shaft; the bottom, which is dome-shaped, is carried upon wrought-iron girders radiating from the chimney, and is secured to the tops of the external columns. This description will be more readily understood when the depths of the tank at its outer and inner walls are given. The former, or that resting upon the external columns, being 38 feet, while the latter, next the chimney-shaft, is about 26 feet. These tanks are calculated to hold, when filled, a body of water of the enormous weight of 1,576 tons, or a bulk of 57,228 cubic feet, equal to 357,675 gallons. The supply is forced from the upper reservoir by the same engines that raise the water to the lower water-tanks and the building; and the same pipes form also the means of conveying the water to the fountains. They are arranged within the outer columns, forming an interior circle, apparently of columns, but rendering in reality no assistance towards the stability of the structure.