Throughout the entire length of the canal, hard red sandstone forms the bedrock, and the formation, of course, varies according to the nature of the stratification. For instance, at 1½ miles distance, where the canal works are inside high-water mark, all layers of deposit have been washed away, and only from 2 feet to 4 feet of black sludge overlies the rock. Occasionally the rock dips and leaves the bottom of the canal in the softer deposits, in some places beds of what has been termed black river sludges, but which are, in all probability, peaty deposits, are sandwiched in, and underlie deposits of from 15 feet to 16 feet of clean river sand. At 5½ miles between Stanlow Point and Ince Lighthouse, large beds of blue loam are met with, varying in depth to 25 feet; and at 6 miles black sludge comes in again, about 20 feet in thickness. At 6½ miles there is a peculiar erosion of the underlying sandstone, apparently from some creek having cut across the line of canal. At 8 miles the section overlies a bed of gravel, and at 9 miles the bottom of the canal runs into a large deposit of sand. From about 10 to 10½ miles the strata becomes very soft, being sludge, sand, and gravel mixed. At 11 miles 45 chains the bottom of the canal is again very soft ground, the sandstone suddenly dipping and not appearing again until about 12 miles. At 13 miles 70 chains the first of the deep cuttings begin, the bottom of the canal being 67 feet below the surface of the ground, and the strata is much less complex than along the estuary. It is near to this place that the canal leaves the waters of the Mersey, and takes an independent and almost direct course to its terminus. From 15 miles, 50 chains to 16 miles there is again a very considerable alteration in the strata, the rock dipping sharply, and softer deposits coming in. At 15 miles 68 chains, where a bore was put down, no rock was encountered to a depth of 88 feet. Following along from 16 miles, where the bedrock rises, a fairly even contour of its surface is maintained, together with overlying strata of soil, sand, and gravel, to near 18 miles 20 chains, where the London and North-Western main line, and the Birkenhead, Lancashire, and Cheshire Junction railways are crossed.