The ventilation produced in a mine as a result of a difference in density
of the air in the upcast and downcast shafts, brought about by natural
causes. Natural ventilation is feeble, seasonal, and inconstant.
Nelson
A variety of resin. Tomkeieff
An orthorhombic mineral, Ag2 Se ; pseudocubic; black; lustrous;
forms heavy, sectile granular masses; also in thin plates; epithermal; a
major source of silver in some deposits.
A representation on a horizontal plane, and according to a definite system
of projection, of a portion of the navigable waters of the Earth,
including the shorelines, the topography of the bottom, and aids and
dangers to navigation; it may be derived from hydrographic, topographic,
or aerial surveys, or a combination thereof. Seelye, 2
One nautical mile or knot equals 6,080.20 ft (1,853.248 m); 3 nmi equal 1
league; and 60 nmi equal 1 degree of longitude (at the equator).
Crispin
Any of various units of distance, used for sea and air navigation, based
on the length of a minute of arc of a great circle of the Earth and
differing because the Earth is not a perfect sphere: (1) a British unit
that equals 6,080 ft or 1,853.2 m; also called Admiralty mile; (2) a U.S.
unit, no longer in official use, that equals 6080.20 ft or 1,853.248 m;
and (3) an international unit that equals 6,076.1033 ft or 1,852 m; used
officially in the United States since July 1954. Webster 3rd
A monoclinic mineral, (V,Fe)10 O24 .12H2 O ; rare;
weakly radioactive; soft; a fibrous mineral with a silky luster;
associated with corvusite, hewettite, tyuyamunite, rauvite, steigerite,
and limonite.
An assumption in the design calculation of beams. It states that the
stress at any point due to bending is assumed as being proportional to its
distance from the neutral axis. Hammond
The National Coal Board of the United Kingdom. Nelson
A boring tower developed by the National Coal Board of the United Kingdom
to make test drillings for coal from positions off the coast. When
drilling is in progress, the tower is resting on the seabed. The base is
divided into four airtight sections, which are filled with water when the
tower is in position for drilling. The water is pumped out to give
buoyancy when the tower is refloated for towing to a new drilling site.
The tower is designed to withstand gales of 80 mph (128 km/h) and waves of
30 ft (9.1 m) from crest to trough, and it can be used in any depth of
water up to 120 ft (36.6 m). The overall height of the tower is 189 ft
(57.6 m), and its total weight is about 570 st (517 t). It has reached
over 3,000 ft (915 m) drilling depth with core recovery. The first
borehole was put down in the Firth of Forth, Scotland. Nelson
This butane combustible gases recorder has a small flame of burning butane
gas, which is controlled to give constant heat output with varying ambient
temperature and humidity, and with varying butane gas pressure. The heat
output is measured by means of a group of thermocouples in a chimney above
the flame. The presence of methane in the atmosphere, which has access to
the flame via suitable gauzes, increases the voltage generated by the
thermocouples. These changes are recorded on a rotating chart calibrated
in percentage methane. Roberts, 1
In oceanography, a high tide occurring at the moon's first or third
quarter, when the sun's tidal influence is working against the moon's, so
that the height of the tide is below the maximum in the approximate ratio
of 3:8. CTD
nearest neighbor interpolation method
A method of assigning a sample value to a point in space. The value
assigned is equal to the value of the spatially nearest sample data point.
This method is sometimes used as a computer equivalent of the polygonal
method of interpolation.
A washability term popularly defined as the percentage of material in the
raw coal within + or -0.1 of the separating specific gravity.
Nelson
Near-sized; grains close in cross section to a specified screening mesh,
which tend to blind apertures and slow down sizing.
Syn:near-mesh material
Material approximating in size to the mesh aperture. BS, 5
Cement slurries containing no aggregate, such as sand or gravel.
Syn:neat cement
A slurry composed of any cement and water. Syn:neat cement
Brantly, 1
The excavation lines of a tunnel within which the rock removed is paid for
at the agreed contract rate. See also:overbreak
A type of mixed rock whose fabric is characterized by indistinct, streaky
inhomogeneities or schlieren and in which no sharp distinction can be made
between the component parts of the fabric. Adj: nebulitic. AGI
a. A lava-filled conduit of an extinct volcano exposed by erosion; also
called chimney rock or plug. See also:plug
b. A pipe of igneous rock crossing bedding planes. Mason
c. The narrow entrance to a room next to the entry, or a place where the
room has been narrowed on account of poor roof. Fay
d. A narrow stretch of land, such as an isthmus or a cape.
Webster 3rd
e. A narrow body of water between two larger bodies; a strait.
Webster 3rd