determine by a formula the permanent safe maximum height of an embankment; the values named are, however, an approximately reliable indication of the height, and are based upon the assumption that the slopes are sufficiently flat to be stable, and that the embankments are deposited in the ordinary way, the width of the formation or top being not less than about 15 feet. It is seldom economical to make an embankment more than 70 to 90 feet in height, except for short lengths, and where deep cuttings cannot be avoided, and it becomes a question of tipping spoil banks or main embankments, or the foundations for a viaduct are known to be of a treacherous and doubtful character. The heights named have been calculated under the worst conditions, _i.e._, that any weight upon the formation will be directly communicated to the base as in the case of a column, and not through the cross-section of an embankment, and over the whole area of the base; however, there is always the danger that the central portion may subside, as the weight upon it is the greatest, and that the slopes may be disturbed and pressed out, especially in soft or soluble earth likely to be quickly affected by moisture. The soil is considered to have no reliable cohesion. In this country the limits of general practice for the height of embankments when unaided by retaining walls or other support, but with the slopes soiled, covered with grass, and only externally drained, has been as follows:— Surface soils, about 20 to 30 feet. Boulder clay from 25 to 30 feet. Yellow, or ordinary clay, 30 to 40 feet. Ditto, ditto, in cuttings, 60 to 65 feet. Chalk, 30 to 40 feet. Gravel and sand, about 60 feet. Ditto, in cuttings, 80 feet. These have, however, been exceeded in many instances, especially upon the lower side of an embankment upon sidelong ground. Probably the highest artificial embankments unsupported by walls or any protective works, are quarry and mining-tips, and ballast-heaps. These have been cast out in all weathers, and allowed to assume any slope or shape, and to a height as great as 100 to 120 feet, and have remained stable, although usually in an exposed situation, but almost free from vibration.