The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1917-08-02
Misfires; Discussion of Vital Subject In.
volving Efficiency and Safety in Mining
mining and Scientific Press)

simple matter but the numerous ar
ticles and letters that have been pub
ushed in the Mining and Scientific
PRESS during the last six months in
dictate wide variety of opinion. Th'
object universally sought is etficienc,
with safety, and that it attainabl'
through practice conforming to thu
lassons of experience. 1t is import
ant to note that valuable experience
IN blasting comes not alone from the
daily work of the miner, but is de-
rived equally from the elaborate tests
made by manufacturers of explosive
materials. The sum of all these OBJ
seryations, critically examined and
sifted by trained technologists, has
resulted in the development of BODY
Of rules that may be accepted as 'au-
thoritatiye. The wrong way of using
explosives is more general than the
right way, and faulty custom Is diff
cult to correct because OF pre1udices
held by the miners. Accustomed as
so MANY of them are to wrong meth
DDS of charging holes, they resent at
tempts by their foremen to shake
them from familiar habit. The man
ager of a mine, however, is entrusted
with responsibility for securing an
economic result He can not concede
free rein to his workmen in using or
misusing materials according to their
whim. A misfire represents not only
a waste of explosive, but loss OF time
on the part of employees in searching
for the unexploded charge or In dig
ping II out; the cost of drilling the
missed hole has been thrown away;
and the ground broken per pound OF
nowder on that shift Is less That Is
not the whole of the indictment. me
ma iority of misfires are the result OF
methods in themselves opposed to the
most economical use OF explosives
Errors eliminating in a mishre IN
yolye a loss +, in efficiency distributed
through the entire round OF shots. un-
der the best management scrupulous
attention is given to the proper use
OF explosives and the tonnage OF ore
and waste rock broken per pound OF
powder and per foot of fuse are SUD-
jects of daily record.
Mr.. E. F. Brooks rightly insisted on
the use of high force caps. He re-
commends 5X and OK. His method
of inserting the cap into the primer
is similar to one suggested by the bu-
reau of mines, punching a diagonal
hole with a stick near the end of the
cartridge; but he advises loading an
other stick of powder on top of the
primer. Mr.. w. S. Weeks criticizes
this practice, as does Mr.. Edward Hig-
gins, adhering to another recommend
alton by the bureau of mines, with
which apparently all powder manu-
facturers are in agreement, that is, to
place the cap centrally in the end OF
the last stick in the hole, tying the
paper of the cartridge end around the
fuse. AS expressed by Mr.. Weeks,
the cap should point in the direction
in which the wave of defamation Is to
be propagated That accords with
the principles governing the detona-
ton of high explosives, as demon
strated experimentally by Bertholet.
The explosion of a charge of dyna-
mite or blasting gelatine, though 1t
may seem to be instantaneous, Is not
SO in reality. A measurable time IN
terval elapses in the transmission OF
the wave from it's initial point to the
end of the charge; moreover, the wave
progresses in the direction of the ini-
tial impulse; it does not expand uni
formly in all directions from the place
of origin. Unlike the spherical waves
Of compression generated by an earth
quake shock, it is rectilinear in its
motion. The illuminate is exploded by
the fire splitting from the end of the
fuse, that Is. by an incandescent
spark. The heat associates that part
of the illuminate with which the fire
comes into contact, generating still
more intense heat by the highly exc
thermic reaction; the explosion pro-
ceeds through the train of sensitive
molecules with increasing velocity to
the bottom OF the charge, from which
a blow OF enormous intensity is deliv-
cred in the direction of propagation.
This is easily demonstrated by the
familiar experiment of placing cap,
with fuse attached, in hole bored
through a block of one-inch plank, set
upon a sheet of mild steel. On ex-
ploding the cap will punch hole
through the steel without doing seri-
GUS injury to the wooden block.
The velocity of the initial impulse
determines the velocity Of the deton-
ating wave transmitted through the
charge of powder. The heat generat-
ed, and the expansive effort OF the
confined gases that develop the 'explo-
slve energy, merely react upon any
part of the powder lying out Of the
path of progression of the decorating
wave. The result Is an explosion Oh
a lower order for that residual por-
ton OF the charge. The degree of ex-
plosion depends on the velocity of the
wave, and the velocity Of the wave
that causes defamation of the explo-
sive lying in the path of the propaga'
ttor to not transnitted TO the powder