A gas introduced in small quantities into the main body of air to
determine either the air current or the leakage paths in a ventilation
system. BS, 8
This method, as applied for the measurement of airflow in headings, can be
used for determining velocities below the working range of the vane
anemometer. The tracer used is normally nitrous oxide. The technique
consists of releasing a quantity of tracer gas, either instantaneously or
over a timed interval. The tracer then diffuses throughout the airstream
until a position is reached where it is uniformly dispersed over the cross
section of the airway. At such a position, samples are taken and these are
put through the analyzer to determine the gas concentration.
Roberts, 1
In ground water hydrology, a field technique for estimating transport
parameters by injecting a tracer (e.g., dye, radioactive substance, or
chemical not naturally present in the flow system) and monitoring the time
and concentrations at a downgradient location. Domenico
In a fault, that component of the net slip that is parallel to the trace
of an index plane, such as bedding, on the fault plane.
See also:trace-slip fault
A fault on which the net slip is trace slip, or slip parallel to the trace
of the bedding or other index plane. AGI
An extrusive rock, intermediate in composition between trachyte and
andesite, with sodic plagioclase, alkali feldspar, and one or more mafic
minerals (biotite, amphibole, or pyroxene). See also:mugearite
AGI
An extrusive rock intermediate in composition between trachyte and basalt,
characterized by the presence of both calcic plagioclase and alkali
feldspar, along with clinopyroxene, olivine, and possibly minor analcime
or leucite. Approx. synonymous with hawaiite. AGI
A group of fine-grained, generally porphyritic, extrusive rocks having
alkali feldspar and minor mafic minerals (biotite, hornblende, or
pyroxene) as the main components, and possibly a small amount of sodic
plagioclase; also, any member of that group; the extrusive equivalent of
syenite. Trachyte grades into latite as the alkali feldspar content
decreases, and into rhyolite with an increase in quartz. Etymol: Greek
trachys, rough, in reference to the fact that rocks of this group are
commonly rough to the touch. AGI
a. A textural term applied to volcanic rocks in which feldspar microlites
of the groundmass have a subparallel arrangement corresponding to the flow
lines of the lava from which they were formed. CF:trachytoid;
pilotaxitic. AGI
b. Pertaining to or composed of trachyte. AGI
A textural term originally applied to phaneritic igneous rocks by analogy
with the trachytic texture of some lava flows. In such rocks (e.g., many
nepheline syenites), the feldspars have a parallel or subparallel
disposition; trachytoid is now used for all similar textures, regardless
of the composition of the rock in which they occur. CF:trachytic
AGI
A process in which float is followed back to its origin. A prospector
moves up slope looking for pieces of float until no more are to be seen.
If, at this point, no outcrop is visible, the probabilities are that soil
or loose surface material covers a hidden outcrop, which can be sought by
digging pits or trenches. Lewis
a. The groove cut in a rock by a diamond inset in the crown of a bit.
Long
b. A pattern applied to setting diamonds in a bit crown, in which the
diamonds are arranged in concentric circular rows so that the diamonds in
a specific row follow the track cut by a preceding diamond. Long
c. The slide or rack on which a diamond-drill swivel head can be moved to
positions above and/or clear of the collar of a borehole. Long
d. See:conveyor track
e. A crawler track. Nichols, 1
A chair bolt or coach screw used in fastening rails. Hammond
Track brakes, similar to those used on surface tramcars, may be installed
on heavy downgrades underground to supplement other braking systems; they
apply blocks to the rails by mechanical, pneumatic, or electromagnetic
power. The normal shoe brake must be designed to work in conjunction with
the track brakes so that the wheels are not skidded when the track brakes
utilize part of the weight of the locomotive. Electromagnetic track brakes
may utilize the braking currents produced in rheostatic braking to excite
the electromagnets, which are then pulled down onto the rails and produce
a strong retarding pull. Sinclair, 5
Steel wire rope, usually a locked-coil rope that supports the wheels of
the carriers of a cableway. Hammond
This type of excavator operates in general the same as a slackline
cableway, except that it uses a bottomless scraper bucket that must convey
its load over the ground instead of through the air. Like the slackline
cableway, this machine is operated by a two-drum hoist that controls a
track cable that spans the working area and a haulage cable that leads to
the front of the bucket. Both cables are reeved through sheave blocks
attached to a high guyed mast or tower at the head end of the
installation. When the bucket comes in with a load and reaches the desired
dumping point, a few rotations of the rear drum of the hoist serve to
tighten the track cable and lift the bucket off its load; then the brake
is released on the front drum that controls the haulage cable, permitting
the empty bucket and carrier to glide back down the inclined track cable.
Pit and Quarry
In quarrying, a rock channeler designed to operate from a track on which
it is mounted; frequently a combined locomotive and channeling machine.
Standard, 2
In mining, a laborer who cleans mine track and switches by shoveling coal,
ore, rock, mud, and refuse, and throwing it to one side or loading it into
a mine car. Also called road cleaner. DOT
A machine to remove gob from railroad tracks, between rails, and to a
distance of 48 in (1.2 m) from the track centers. Digger plates remove gob
to the top of ties, while wings on either side of the machine gather it
from the sides of the track into the track, to be moved by conveyors to a
car at the machine's rear. One person operates the towing motor and
observes the digging, while another controls the digging plate height,
adjusts wing plows, and observes loading. Best, 1
Diamonds set in the face or lead portion of the drill-bit crown.
Syn:track stones
In a crawler mounting, a side frame to which the track roller and idler
are attached. Also called truck frame. Nichols, 1