GAG. — An obstruction in the falls or lids of a bucket or clack which prevents them from working. (See Dredge Sump).

GALLOWS TIMBER. — A crown-tree with a prop placed under each end.

GANISTER OR GANNISTER. — A very hard and siliceous fire-clay found beneath some of the seams of the lower coal measures. It contains stigmaria roots. It is manufactured into fire-bricks of a highly refractory character, which can be imitated by grinding and mixing up fire-stone post with a less refractory clay. This post is also called ganister.

GAS. — Usually carburetted hydrogen is referred to. Occasionally sulphuretted hydrogen has been found in old wastes. This is easily detected, where present, by its smell. Carbonic acid gas, or stythe, is frequently found in great abundance in coal mines, especially where the seams worked are found at moderate depths from the surface; and a pernicious gas has been occasionally found to issue from old wastes which is fatal to animal life, but in which a candle will continue to burn with undiminished brilliancy. This has been considered to be owing to a mixture of sulphuretted hydrogen with atmospheric air, 1-50th part of which may produce a compound possessing the above properties; but as in a case which occurred at Hartley Colliery, the smell of sulphuretted gas was not described as being present where the man was found dead by the side of his burning candle, the inference is that death was caused by some other gas, most probably by carbonic oxide. The author has knowledge of an instance of the existence in considerable quantity of sulphuretted hydrogen in the Top Hard (Barnsley) seam of coal in South-Yorkshire, and also of" white-damp" or carbonic oxide, in the White Ironstone Mine in Glamorganshire. "White-damp" is well known in South Staffordshire, but it is there no doubt the result of the spontaneous combustion or gob-fire, which is always more or less prevalent.

GATEWAY. — "A passage through the goaf secured by a pack-wall on each side, for the purpose of bringing out the coals worked on the long-wall system." (Nicholson.)

GEARS, PAIR OF. — (See Gallows-timber.)

GEORDY. — The safety-lamp invented by George Stephenson. (See Davy.)

GIN. — An apparatus consisting of a drum fixed upon a vertical shaft, to which a lever, called a "start" is attached. A horse yoked to the end of the lever, and moving in a circular track, causes the drum to revolve, and to wind or unwind a single rope, or to wind and unwind a pair ot ropes working over pulleys into a pit, or where required. Gins are constructed with the barrel or drum from 3 or 4 to 15 or 18 feet diameter. Large-sized ones are usually worked by two horses, yoked abreast. Before the application of the steam-whimsie to drawing coals, gins, called also whims, or whim-gins, were used for the purpose.

GIRDLE. — When a stratum of blue or grey metal has interspersed with it bands of post, without partings so as to separate them into complete strata, it is said to be blue or grey metal with post girdles.

GOAF. — A space from which the coal pillars have been extracted. It is usually in the first instance a large dome, resting as the extent increases upon the wreck which has fallen from the roof of the exhausted space. Eventually the pressure to a large extent re-consolidates the whole, the surface subsiding.

GOB-FIRE. — Spontaneous combustion in a goaf. Very rare in the North of England.

GOING-BOARD. — When the crane, fiat, or station, is not at the end of the headways-course at the face, and the coals are brought down to it by a board for one, two, or more pillars, this board is called the going (or "gannen") board.

GOING-HEADWAYS. — Usually the headways-course next the face.

GOWK. — (See Rider.)

GRATHE. — To put in order, to dress; to replace a worn clack or bucket leather.

GRATHELY, GRADELY. Trim, tidy.

GREASER. — A boy who greases the tub axles at bank. A machine, in passing over which the axles are greased automatically.

GREY-METAL. — A slightly siliceous indurated clay of a light grey colour.

GREY-METAL-STONE. — Grey metal very siliceous and gritty.

GREY-POST. — Sandstone of a grey colour.

GROUND-CRAB. — (See Crab.)

GROUND-ROPES. — (See Crab.)

GROUND-SPEARS. — (See Crab.)

GROVE. — A drift or adit driven into a hillside from which coal is worked. A drift into a seam of coal from the outcrop.

GUIDES. — (See Slides.)

GULLETS. — Vertical cracks more or less open. Mostly confined to beds of post, sandstone, or rock. At and near the outcrop of such beds, rainfall or other water passes rapidly into mines beneath.