A double-tube core barrel having the upper end of the inner tube coupled
to the core-barrel head by means of an antifriction device, such as a
roller or ball bearing; hence, the inner tube tends to remain stationary
when the outer tube, which is rigidly coupled to the core-barrel head, is
rotated. Long
A longwall conveyor layout from 200 to 280 yd (183 to 256 m) long,
developed between two tailgates with a main gate in the center of the
face. The main gate conveyor is served by two face conveyors and may act
as an intake or a return airway. The tailgates may serve as supply roads.
See also:double-double unit conveyor; main gate. Nelson
A drill-hole pattern consisting of a shallow wedge within an outer wedge,
which is often used to obtain deep pull in hard rock.
See also:wedge cut
A method of working in which rooms are driven from adjacent headings to
meet at their extremities. Zern
N. of Eng. Two hewers (miners) working together in the same heading.
Syn:hewing double
A fold that plunges in opposite directions from a central point. In a
doubly plunging anticline, the plunge is away from this point; in a doubly
plunging syncline, the plunge is toward this point. Billings
Causing double refraction. See also:birefringent
Alternate spelling of daugh.
The cylinder of coal formed by a coal auger. Nelson
A horizontal, revolving cylindrical furnace having a central flue.
Fay
Eng. A soft dark clay found in veins. Probably derived from the Saxon
deagan, meaning to knead or mix with water. Syn:dowk
See:dowsing
Commonly used by drillers as a name applied to a wooden wand, rod, forked
tree limb, or twig (usually witch hazel) supposedly useful in locating
formations bearing water, oil, or mineral. Also called divining rod;
doodlebug; dowsing rod. Long
See:synchysite
The Dow electrolytic cell is a steel shell about 16 ft (4.88 m) long, 5 ft
(1.52 m) wide, and 6 ft (1.83 m) deep. The electrolyte contains about 60%
NaCl, 15% CaCl2 , and 25% MgCl2 ; it is maintained at a
temperature of 700 to 750 degrees C by controlled firing underneath the
cell. Newton, 1
See:douk
See:tectogene
a. The shaft through which the fresh air is drawn or forced into the mine;
the intake. See also:air shaft; intake. Fay
b. That side of a fault on which the strata have been displaced downward
in relation to the upthrow or upcast side. CTD
The shaft down which the fresh air enters the mine or workings.
See also:upcast shaft
A pipe to conduct something downward, such as: (1) a pipe for leading the
hot gases from the top of a blast furnace downward to the dust collectors
and flue system, and (2) a tube larger in diameter than the water tubes in
some water-tube boilers for conducting water from each top drum to a
bottom drum under the influence of thermal circulation.
Webster 3rd