Being anxious to show by an illustration, which would be familiar to most persons, who are either resident in, or have visited London, what is a gradient, we applied for information to Mr. Wm. Haywood, the engineer of the Corporation of London, under whose direction the Holborn Viaduct and Embankment are now in course of construction. He has kindly and courteously furnished a diagram—a copy of which is annexed at the end of the volume, showing in minute detail the variations of gradient, from Staples Inn to opposite the Old Bailey and Giltspur Street. The total length from point to point is 2,202 feet, a little more than two-fifths of a mile. The steepest gradient is 1 in 15 (352 feet in the mile) for 86 feet, the next 1 in 18 (293 feet in the mile) for 257 feet, and 1 in 19 (278 feet in the mile) for 113 feet. These gradients are all on Holborn Hill, between Hatton Garden and Shoe Lane. The steepest on Snow Hill is 1 in 21 (251 feet in the mile) for 87 feet, and 1 in 24 (220 feet in the mile) for 312 feet. All these gradients will, however, in a year or so, be matters of history, for it is hoped that the Holborn Viaduct will be opened for traffic at the beginning of 1869.[115] [Illustration: GRADIENTS OF HOLBORN HILL & OF SNOW HILL LONDON _Horizontal scale, 352 feet to an Inch._ _Vertical scale, 44 feet to an Inch._ ] It is, however, a misnomer to call it a viaduct. It is true that, by means of a massive construction, the opposite sides of a valley—at their summits more than two-fifths of a mile apart—are connected together on the level. But, in reality, the viaduct is a great metropolitan work, worthy of the Corporation of the City of London, which, although well abused by persons who do not understand its operations, is never-ceasing, to the extent of its means, in carrying out improvements within its limits. A list of the works and changes effected by the Corporation in the last thirty years would show that it has expended millions in altering the face of the City,[116] and in increasing facilities for traffic, especially at points of aggregation. The manner in which the new street that is to run from the Mansion House to Blackfriars Bridge, within City boundaries, is advancing, contrasts markedly with what is doing beyond them. According to present appearances, the City will have completed its work and opened its portion of the street for traffic about the time that the Metropolitan Board of Works will have made a fair start upon what it has to accomplish.