As might be expected, the more argillaceous or clayey marls when exposed to weather influences expand, contract, and act almost as clays, becoming decomposed, disjointed and separated, and when superimposed upon rock, especially if it be inclined, are very likely to slip, and are treacherous and unstable soils, as they soon become in a muddy state and have slimy surfaces, which, when resting upon any dipping bed, cause them to be disposed to move upon the smallest disturbing element being present or becoming increased, such as water or vibration. When a comparatively permeable stratum overlies even hard marl, water will penetrate to the latter earth and the superimposed layer will rest upon an unstable bed, and therefore be likely to slip. Blue, or any marl when found mixed with layers of small gravel and sandy clay is very treacherous, as air and water cause it to swell and crumble, and it becomes in a soft state requiring a very flat slope. All clay marls that swell when wet, and crack and fissure when dry, are unstable, as water percolates to them, and should sand veins occur in marl, water may trickle to a considerable depth and cause the ground to be in a loose and doubtful condition below the formation or bottom of a cutting. Such soil when tipped into an embankment is worse to treat than in a cutting, as it will absorb and retain water so that it is practically impossible to drain or extract it. Professor Ansted has classed clay soils as under:— When combined with 30 or 40 per cent. of sand they are CLAY LOAMS. When combined with 40 to 70 per cent. of sand they are TRUE LOAMS and LOAMY SOILS. But not until they have 90 per cent. of sand in them are they SANDY SOILS. When combined with from 5 to 20 per cent. of lime, the soils become MARLY. But not until they have more than 20 per cent. of lime in them are they CALCAREOUS SOILS. With respect to the slope of repose in clay earths, it may be anything from 1 to 1 TO 12 to 1, and when the clay is mere dried mud and becomes saturated it may not be at rest until it is horizontal. In cuttings, strong compact clay, if not seriously impaired by air and moisture, will stand at from, 1¼ to 1 TO 1 to 1. Ordinary clay, such as the blue clay, with protected slopes and proper drainage, and firm boulder clay, about 1½ to 1 Plastic clay from, 2 to 1 TO 3 to 1. Lias clays of doubtful character, 3 to 1 TO 4 to 1. Superficial beds of London clay, 3 to 1, and not less for any weak clay. In embankments, much depends upon the height, mode of tipping, state of the soil when deposited, the protection afforded and uniform character of the mass, the larger it is the more difficult it will be to drain.