Amador ledger., 1900-02-09
The Explosive Force of Gun
Powder.
THE SEVERAL METHODS OF ROGK-DRILLIHG
An Interesting Paragraph on Specific
Gravity of Solids. How to
Obtain It.

0uH pOWueF mas du explosive lOfCe vi
about eighteen tons per square inch,
when confined. In ordinary quarry
ing or blasting, cubic yard of solid
rock in place, requires from one-quar-
ter to three-quarters rock; the re-
quirements vary from one to two
pounds to the cubic yard. Tunnels
and shafts where the resistance of the
confining walls overcomes, large part
of the force eXerted from two to six
pounds are required to break cubic
yard. 1t is usual to allow about one
and one-forth pounds of powder to each
foot in depth of two-inch drill-hole
A four-inch hole requires five pounds
to each foot in depth for effective
breaking up of the surrounding rock.
These figures apply only to gun pow
der, and not to other high explosives.
ROCK-DRILLING.
Holes for blasting are usually made
from two to four feet deep, and may
be made by hand or by somo form of
machine drill. The usual size of the
drill-hole is from one and one-half to
two inches. The simplest method is
by hand drill, sharpened bar of
steel. which the worker holds in his
left hand, turning partly around after
each blow, while he wields the hammer
with his right hand. The Jumper"
is modified form for larger holes,
where spring or pole is used to bal
ance the weight of the drill, and the
holder simply does the turning and
steadying. The blows being delivered
by one or two workmen. The churn-
drill consists of an iron bar six to eight
feet long and one and one-quarter to
one and one-half inches in diameter,
usually suspended to spring or pole,
which is turned as it rebounds, and is
allowed to drop and cuts by the force
CT its own weight in dropping. A man
in ordinary rock can cut a two-inch
hole from five to fifteen feet deep in
ten hours. This sort of contrivance
can be used to advantage in surface
work, and the figures do not apply to
work in mines, but rather in quarries.
Machine drills will be treated at
another time.
SPECIFIC GRAVITY.
The specific gravity of body is, u.s.
ually, its weight as compared with an
equal volume of water, under certain
conditions as to temperature and alti-
tude. This is applied only to solids and
liquids, hydrogen gas being the usual
standard for gaseous bodies. AS water
is at its greatest density at the sea-
level, and at a temperature of four de-
grees Centigrade or thirty-nine and
two-tenths Fahrenheit, it is used at
the standard, under these conditions:
For ordinary purposes, where sci
entific accuracy is not necessary, any
pure water at ordinary temperature
may be used. To find the specific
gravity of body heavier than water,
weigh first in air, then in water, and
find the difference. This is what the
body loses in weight by reason of the
bouyancy of water, and is really the
weight of the water displaced, or the
weight of volume of the water equal
to the volume of the body immersed.
Then to obtain the specific gravity,
or ratio of weight of the body to
water, work out the following propor-
tions
Difference weight in air : / X (specifc
gravity)
In the absence of an hydrometer one
may find the specific gravity of liquid
by the following method
Weigh piece of some metal or solid,
in air. Then weigh in pure water and
note the loss, calling it 3D." Then
weigh in liquid to be tested and note
the loss, calling it ''d' then
d: d. :: Specific gravity of water) x 1.-THE
specific gravity sought.)