The Viaduct in its formation will include vaultage beneath each footway for the accommodation of the future houses on either side of the roadway; outside these vaults will be a subway for the gas and water pipes, and between each subway, and forming the centre of the Viaduct, the roadway will be carried on a series of arches. The general height of the subways will be about 11 feet 6 inches and their width 7 feet; they will be of brickwork, excepting where they are carried over the London, Chatham, and Dover Railway; there they will be of iron. In each subway provision is made for water, gas, and telegraph pipes, all of which will be so placed that their joints can be inspected, and repairs made without difficulty. The mode of construction of sewers, drains, and street gullies is such that it will never be necessary to break up the surface of the Viaduct to repair or cleanse them. Farringdon Street will be crossed by a cast-iron bridge of an ornamental character. It will be in three spans, supported by piers, one row being on the outer edge of each footway. These piers, as well as the outer abutment piers, are to be formed of polished granite. The height of the bridge next to the curb stones will be 16 feet, and in the centre the minimum height will be 21 feet, considerably more than sufficient for the traffic. At each corner of this bridge flights of steps will be constructed for pedestrians to pass between the upper and the lower levels. These will be enclosed in stone structures, ample light and ventilation being given to them. Shoe Lane, now at its northern end but 14 feet wide, is to be increased to 30 feet in width, and to be continued northwards, under the Viaduct, to a new street which is to be formed from the corner of Hatton Garden to Farringdon Road. A complete net-work of streets is to extend from the Viaduct to all the existing adjacent streets, and as at the place at which Holborn ends and the Viaduct commences several of these streets concentrate, with the view to remedying the inconvenience which would arise from a too limited area for traffic; and to add to the character of the work in an architectural point of view, Mr. Haywood has formed at this point a large circus 180 feet in diameter. This open space will, in addition to its other advantages, afford an opportunity for architectural display that we are sure will be judiciously availed of. The magnitude of the work may be represented, in one shape, by the number of bricks required for its construction. From seventeen to eighteen millions, of which rather more than two-thirds are in the actual viaduct, and somewhat less than one-third in the constructions connected with the side streets. Of course these amounts are independent of what will be used in the houses and buildings to be erected hereafter. These will be millions in their numbers also. Of gradients in reference to railways we speak hereafter.