The New York herald., 1876-09-20
THE GREAT MINI.
Precautions Taken to Guard
Against All Accidents.
RENDING THE ROCK.
How the Columns and the Roof Rock
viii Be Destroyed.
FLOODING THE MINE.
The Operation Performed bv
Means Of Siphon.
THE BATTERY BOMBPROOF.
Boxing the Wires Leading
Through the Headings.
OPINIONS OF ENGINEERS.
How the AStOrians Regard the Approaching
Big Blast.
THE BATTERY BOMBPROOF.
Boxing the Wires Leading
Through the Headings.
OPINIONS OF ENGINEERS
How the AStorians Regard the Approaching
Big Blast.

Zig Blast.
fhs destruction OF every part OF Halles Point reef
above the Lowell Of twenty oight feet soundngs by the
sultancous explosion OF several thousand holes filed
with heavy charges of nitro glycerlne and dynamite is
An undertaking that neccssates the utmost precauon
10 guard against accidents and failure With regard to
the provisions against the former they must be
sidered In two classes local and general and such
they will be explained In the present article The first
care of tho engineers is TO protect the exploding
apparatus from injury by any parts of the rock
that may be projected from tho recf by the
orce OF tho explosion This they have accomplished in
he manner hereinafter described In large mass OF
such that OF Halett's Point reef which
has been excavated with tunncs transverse CALLER
los the effects produced by equal charges of explosives
In all the holes will differ very much In character It
must be remembered that the resistance offered by
mass Of rock 10 the orco of the exposon is meas-
urcd by the shortest distance from tho centre of
sharge to tho free surface by tho cohesvcucss Of
Ihc atoms Of which the rock is formed The FIRST is
ermed the line OF least resistance that along which
Sho energy Of the expanding gas generated
by the combustion Of tho explosive finds the oast OBJ
staclc to It's forco II hollow sphere of iron, shc
br instance with eccentric Interior exterior
fracture Will ako place whore the shell thinncst and
bowl shaped portion will remain unbroken. In like
manner, II cubica block OF stone is perforated OBJ
qusly TO the plano OF Its Sides leave greater
mass OF the stono sido of the holc
ihan the other the weaker portion will bc
Ihattcred 10 pieces by the explosion Of the
Iharge, while the heavier and stronger part will
be only cracked intopieccs Now, II the density
OF the gness rock al Haets Point equal through
Sut the entire 1t would be tho thing pos
nble for experienced mining engineers to calculate
nd indeed, TO regulate the effects that would DO pro-
luced by the explosion. They could graduate their
shargcs both 70 strength and regulate thom To-
cation in oxact accordance with the necessities OF the
case, and feel confident in tho results being they
desired TO produce them. But with forma-
ton variable in Its nature and this varia.
uon being complicated by stratincation,
and further by the peculiar directions of tho galleries
and headings with relation the limo Of stratncaton
the difficulty OF determining positive results
. hundred fold The axis Of the rccf in this
is coincdent with its stratincaticnthat s projects
into the channel In the same direction as the align
ment Of the layers OF rock and consequently, somo OF
the headings have been driven al right angles with this
line aud the stratiAcation. While, therefore,
tho explosion will split somo OF tho supporting columns
into regular blocks OF the same thickness of
The several strata, tho effort Of the force
Ia others will be to tear the rock
what might bo called It's grain. TO mako this
lhto clearer let us suppose Two blocks OF wood cut
from tho Same piece, and with the character Of
fbrc. Now. one Of these is simply split by the action
OF wedge with comparatively tlo effort, while If
try tho other end from end tho resistance viii
DO immense. In the same way the explosives will
operate at Hallotts Point reef tho rock columns
that support the ROOT. To overcome tho differ.
cnce In tho resistance Of the rock tho engineers
have made careful calculations by which they
determined the requirements for each column scpa-
rately Perfect diagrams Of the made CIV
ing its variations Of outline at several heights from tho
ground line to where 1t connects with tho roof Tho
qualification was Indicated on these, together with
the peculiar degree Of cohesrveness In tho
Particles OF each stratum, SO that reality the
graduation Of the charge s made TO depend
local conditions each set OF cartridges having a
specified amount OF work to perform given mass
Of rock. II the utmost foresight therefore, eau &C.
tho best results far the destruction OF tho
columns concerned, tho operations Haetts Point
promise to be eminenty successful
With regard to tho root rock or the untouched
described In the columns exist in u also,
with tho additional complication OF Its arch
Could the columns be removed from under this rocky
shell the probability Is that would not fail TO sustain
ITS weight that OF the water In
dealing, therefore, with the roof General Newton has
wisely limited his prospective results TO general frac
ture Of tho shell with moderate charges Introduced
~ considerable Intervals These charges being fred
simultaneously with those that shatter and rcnd the
rock columns beneath are intended TO assist n break
Ing up tho roof while It subsidies on the debris Of the
columns. There is NO intention whatever to blow the
roof of the columns ana scatter II In small pieces
all around l.. is hore that VIII be found
the value OF this plan as n local prccauton
against accident. In order that any portion OF
tho shattered columns should DO thrown by tho
should first be blown through covering Of ten
fost thick Of rock which Immediately ovcrics II with
force that could not be impaired by monster rlied
gun. Even though AN opening large enough 10 per-
NIT the passage through OF such rock projcctile
I, would be met above the rock by an inrash.
ing column OF water many icet deep, which
would retard its motion as 20 cause to rise but
few feet above the river surface In ordinary blasting
operations. such those commonly witnessed In tho
work street grading and cutting up town, It
Is usual the loaded hole before firing with
number OF logs chained together prevent tho
stone from scattering with the shock the explosion
Now, tho root rock Hallcts Point acts In the very
same way tho heavily loaded columns, and will pre-
vent any danger from arising whom tho latter arc being
blasted
FLOODING WORKINGS
The introduction OF water into every part OF tho
works before hiring must also bo regarded as local
lrecaution OF tw0o.d value. In tho nrst place II
What Is called lamps the great mno in the most per-
icct manner by nling II with powerful resistant to
the escape OF he before they have pshed
their work In the absence OF tampng the line of least
tcsstance would be along tho axis Of the blast holc
tsc und therefore, instead OF bursting through the sur
rounding rock, the iorco OF the explosion would
Of gun In loaded rite. for Instance tho pallet
acss as partial tampng ior the charge iuclosing
TO concentrate the energy OF the explosion. But
e resistance offered by the bullet IS very much lest
,an that offered by the barrel tso tho line OF lcass
resistance Is IA tho direction OF the bullet and along
the barrel. Ii the bullet was tightly wedred in the
gun, so that the expIosion could not dsIodve IL
quickly, the gun would burst nkc tho rock when
the charge Is exploded But Il will be asked
and very naturally, how water will oncr as much re-
sstancc Ia the depths OF the Haetts Point mine as
The rock that surrounds the cartridge Water, when
incoscd III circuniscribeS place and wltnuut any
Chance OF moving, becomes rs inert sono Its pres
sure increases IN direct proportion to It's dcpth so
tnat ut tbs bottom OF tho shaft say thirty SIX feet be-
low high water level At the time Of tho cxplosion
each square foot OF surface ut that depth would be
pressed with weight equal to about $50 pounds
or "A llto more Than uftQcn pounds mar suunro inch