The surface soil, which has an average depth of six feet, is a bright red ferruginous sand, composed of somewhat fine rounded grains of quartz. Next a thin layer of calcareous tufa is found in some places, but not invariably; then follows a layer of laminated trap or blue whin, evidently an intrusive rock varying in thickness and depth in different localities. This layer, which is of a very decomposed and friable character, runs down diagonally in some parts, in broad sheets through the blue shale. A very even layer of light colored shales, on an average twenty-five feet thick and very soapy to the touch, comes next. These shales are of various colors, as pale bluish white, olive, yellow, gray, etc., and the laminæ are often thickly marked with different designs formed by decomposed iron, probably pyrites. Some of these markings are very delicate and beautiful, often resembling minute ferns or _algæ_, and in this bed various fossils have been found. Beneath these we have a vast layer of blackish, or neutral tint, carboniferous shale, containing four or five seams of “iron band” (bog iron ore, or limonite) from one inch to one foot in thickness. The nodules forming these “bands” are very full of cavities, and are of different colors, yellow, red, and blue, with a dull appearance and rather soft. In some specimens the colors are beautifully bright, especially in the cavities. Many fossils have been found in this shale as well at all depths. Very many nodules of a similar shale, but harder, varying in size from an inch to one or two feet in diameter, are found imbedded in this rock, or “main reef” as the miners term it, in contradistinction to “floating reef,” an erratic rock which will be mentioned when we come to describe the diamondiferous ground. These nodules often assume the forms of casts of shells, such as those of oysters, mussels, etc., and give the idea that the main body of the reef was formed from the grinding down of an older rock, of which these nodules are the remains, an assumption which there is much further internal evidence to show in all probability to be correct. It may be as well here to mention that all the above shales, after drying by exposure to the air, disintegrate and form a fine friable mould, or even mud after much rain has fallen. This property of becoming friable after exposure is the cause of the frequency of “land slips” falling into the mine. When a fall or slip does take place, the bulk of such mass is usually in very small pieces, not in large solid blocks, which would be the case if the reef were not of a nature so extremely rotten and easily decomposed.