X. “Coal Apples” from Lugton Water

Abstract

Near Mavisbank on the Lugton Water there is an outcropping thin seam of coal, the position of which is a few fathoms under the Highfield limestone. This coal, originally a kind of inferior gas-coal, has been pretty much altered by the influence of an intrusive sheet of trap, which, though not touching it at this point but lying some distance below it, has apparently been the cause of it having lost its volatile matter. Instead of taking a columnar structure, however, which is a common feature in altered coals, it has assumed a sort of globular form, the “globes” not being perfect spheres, but resembling somewhat the shape of a kidney potato. These vary in size from about 1 inch to over 3 inches, and have several outside coatings which can be easily peeled off. Sometimes their surfaces show considerable depressions, each “coal apple” being contained in a semi-cubical piece of the mineral. In the process of extraction many of them split along the Original bedding-planes, but always in the direction of their long axes. The reason why the coal assumed this semi-globular structure has probably, in the instances above noted, been owing to the proximity of the trap, which has caused a softening of the mineral, and has allowed the particles of the coal freedom of motion, resulting in their taking up new positions. I have, however, seen “coal apples” from a free coal, which did not show signs of ever having been affected by heat. This 250-word extract was created in the absence of an abstract