The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1876-09-20


HOLES PRoBABLE n EsULTs OF TIE
GREAr BLow-uP-AN IMMENSE COLUMN
:. oFWATER LIKELY TO BE THROWN ! HIGH OH
INTO THE AIR. .,ss
.,,-f fFronl the New York Tmes.j
sThe reef which is the scene Of Genera.
Newton,s operations lies Immediately Oh
HalIet's Points, in fact, q submarine por-
ton OF it. II It is much in the shape OF
semi.ellipse, the base running almost III
straight line from east to west, and the apex
pointing nearly due north. The area Oh Tue
reef is about three acres, two ana three
quarters Of which have been undermined.
a fair conception of the plan OF operatlons
can best be given by comparing the inead-
ings and eross-headings or galleries 10 tne
lines Of Longitude and latitude on aigloDe.
The headings all radiate from the smart,
which, is in the centre sof the base OF the
eIlipse, and the galleries extend In semi
circular form around the shaft. Il
81 THE SHAFT AND THE TUNNELS.
The shaft is an irregular pentagon IN
shape, 1T by go feet, and having a depth OF
"A feet below low water. a light wooden
staircase leads down into the shaft, the Dot
tom at which would be perfectly dry but
for the wet sawdust with which 1t is cover
ed The sawdust is precaution against
corcussion in case cartridge should be ac-
cidentallv dropped. From this shaft ten
main tunnels Tadiate, the tunnels varying
in length from 1876 feet to 800 feet in length,
the average length being 270 feet. Tne
width of the tunnels is about IA 1eet,
and their height varies from ~ IeeI
at the opening to 7 feet at the emu. Inc
floor of the mine falls gradually, tne
roof of the excavation more raplaly.
following the bed OF the river above, anu
keepine I'D a general average OF ten rect OF
solid rock below the water. Cross galleries,
of about the same height and width as the
tunnels. traverse the mine at intervals OF
thirty feet, leaving the roof supported by
enormous columns Of solid rock. These
! columns. however, are cut through by sec
ondary tunnels and galleries, increasing the
number OF rock piers supporting the ROOF
to one hundred and seventy-three, OF about
ten feet in thickness, and giving an aggre-
cate length of tunnels and galleries OF 7,425
| feet-4.S5T feet of tunnels and 2,56S feet OF
galleries. In order to create this network
Of tunnels and galleries it was necessary to
blast out and remove no less than Al, 46l
cubic wards OF rock This work was be-
gun seven years ago, and was hnlshcd III
June, 1915; and since that time the pillars
have been drilled in all directions prepar-
atory to the insertion Of the cartridges for
4 the grand and final blast. The pillars ana
the outside walls OF the mine have been az,
ranged in what are termed battery groups
4 flint is. for connection with the electric bat
tery which is to fire the blast. There are
one hundred and eighty-four OF these
groups, each group being drilled for twenty
charges, making $3.50 charges in oil. But
two. and generally. three, cartridges are
charged into the same hole, according to
circumstances and the Judgment OF the fore
man who has charge of the mining depart
ment; so, till the charging is actually I'm
ished, no accurate figures as to the exact
amount OF explosive agents to be used can
be given. - tt'..
THE EXPLOSIVES AND THEIR EFFECT.
The varying hardness Of the gneiss forma-
ton OF the reef has led to the employment
| OF three kinds OF explosives in charging for
the blast-dynamite, rend-rock, and vulcan
Dowder: the first for the harder and the two
latter for the softer rocks. All these three
explosives have nitro-glycerine as compo-
nent part, though they differ much in APP
pcarance. Dynamite has the appearance of
| 4 fine quality Of brown sugar; the others
resemble the boot backing in vogue among
the gamins OF the City Hall Park-a thick,
black paste. Dynamite, or giant powder, as
| it is often called, is now recognized as not
only the most powerful, but as the safest
of known giant explosives. 1t is a
compound of pulverized slick, silicious
ashes, or more generally infusorial
earth, saturated with three times its weight
OF nitro-glycerine that is, twenty-five per
cent. of infusorial earth and seventy-tve
per cent. of nitro-glycerine. Under favor
able circumstances, the effectiveness Of dy-
Mantle is greater than that OF pure nitro
glycerine, while it is not so dangerous, the
fundamental explosive agent still being the
nitro-glycerine. Most people are more or
less familiar with ordinary gunpowder as
an explosive, and a comparison between it
and nytro-glycerine will give some concep-
ton OF the extraordinary power of the lat
ter, OF course remembering that the effects
of an explosion are brought about by the
great and almost instantaneous expansion
Of liberated gases, producing an enormous
pressure in all directions. The following
table will show the constituent gases yield
ed by 100 parts Of nitro-glycerine on COM
bustion: - -
Constituents. BY weight. BY volume.
l Sh