which the Thick coal was found uninjured either by trap or by "rock and rig."
On a subsequent visit to these pits in 1858, I examined, with Mr. Cooksey, some gate-roads that had been driven in a southerly direction, or towards the part of the ground which is capped by basalt. The sandstone called "rock and rig" came in in larger quantity in that direction, as before described, p. 50, and the veins of white rock trap became very numerous. In one of the gate-roads a horizontal vein of trap, about a foot, or a foot and a half, in thickness, ran horizontally and regularly in the middle of the coal for 40 or 50 yards, looking precisely like a deposited bed, but then suddenly cut up across two or three beds of coal, sent off a number of irregular strings and bosses into the coal, and then shot off again horizontally near the roof for some distance, see Fig. 14. The mass of this coal was a perfectly clean, bright coal, with brilliant surfaces on the face and joints. For a distance of 6 inches to 12 inches, however, from the trap the coal was "blacked," that is to say, it was dull and friable, with an earthy look, having neither the dice-like division into lumps, nor the brilliant shining surfaces which the rest of the coal had.
Fig. 14 will give the representation of these facts from a sketch made on the spot with as much care as I could draw it, the white part representing the trap, the black border round it the altered coal, and the mottled part the coal retaining its brilliancy.
Fig. 14.
SCALE FIVE FEET TO ONE INCH.
Fig. 15 is taken from another sketch made on the same occasion, showing the termination of a considerable mass of this trap, and a little isolated boss of it in the coal.
Fig. 15.
SCALE TEN FEET TO ONE INCH.
