The layers of slate in the quarry were eloquently described in 1758: "The strata in the following order: the green sod, one foot; a yellow brown clay, two feet; then the rock, dipping inwards into the hill towards the south-west, and preserving that inclination from top to bottom: at first the rock is in a lax shattery state, with short and frequent fissures, the lamina of unequal thickness, and not horizontal: thus the rock continues to the depth of ten or twelve fathom, all which is good for nothing, and entirely to be rid off; then comes in a firmer brown stone, which becomes still browner in the air; this is fit for slating houses, and the largest size for flat pavement never sweating as the cliff slate, which is exposed to the sea air. This is called the top-stone, and continues for ten fathom deep, the stone improving somewhat as you sink, but not at the best till you come to twenty-four fathom deep from the grass; then rises what they call the bottom-stone, of a grey blue colour, and such a close texture, that on the touch it will sound clear, like a piece of metal. The principal horizontal fissures, which divide the strata, run from ten to fifteen feet asunder; they are no more than chinks or joints, and contain no heterogeneous fossil. The stone of this quarry weighs to water as 2-(62/121) are to 1, is not subject to rot or decay, to imbibe water, or split with falling, as the bottom-stone of Tintagel, and other quarries; but for its lightness, and enduring weather, is generally preferred to any slate in Great-Britain."