JACK. — During sinking, whilst the two pits or a pit and a staple are being sunk simultaneously by means of two gins, one of them, to prevent mistakes, is usually called a jack.

JACK HEAD. — (See Staple.)

JACK-ROLL. — A winch used for sinking moderate depths, both underground and at bank. Called in West Durham, "Row and Stoches." (Roll and Stanchions?)

JACKANAPES. — A succession of frames with pulleys or sheaves suspended therefrom to carry an overhead rope.

JENKING. — A fast jenking is a narrow place driven lengthways in a pillar of coal, but unholed into the board on either side of the pillar. A loose jenking is a similar place driven along the side of the pillar and open to the board along that side. These places are mostly driven in working pillars. Wherever practicable, when a jenking is necessary, it should be driven loose sided, a fast jenking very frequently causing a creeping to take place, and almost invariably rendering the pillar or wall in which it is driven crushed and useless, although to this there are exceptions.

JET. — A species of coarse cannel coal, nearly approaching to a black stone. It burns wit h a bright flame, but loses little bulk in the fire. Some of these black-stones or shales contain upwards of 20 gal lons of oil to the ton.

JOWL. — A sort of "tattoo," beaten with a hammer, and in response, upon the faces of two places or drifts near holing, or intended to hole into each other, by a person in each place, for the purpose of ascertaining by the sound their relative positions.

JUD. — A portion of the seam kirved, nicked, and ready for blasting, called also 'vantish, 'vantage, or advantage; also a portion of a pillar in course of being worked away in the broken mine.

JUMP. — To drill a hole for blasting with a jumper.

JUMPER. — A drill made of greater length than that commonly used, and having the head swelled out to make it heavy. It is driven by the hewer with both hands. The plan was introduced into the North by South country miners about the year 1832, but has not been much practised.