The workingman's advocate. [volume] (Chicago [Ill.]) 1864-1877, 1870-05-14
The Great Submarine Blast in the Har.
Dor Of San Francisco.

It's well known that extended preparations
have been making for several months under
the direction Of Col. Van Schmidt, q: X.
to remove what 10 known M Blossom Rock
'shs most dangerous obstruction In The mag
ni6cent harbor Of San Francisco.
That 30 important an engineering worl
should have brought to 50 successful a con
clusion reflects great credit upon the skill
Of Col. Van Schmidt, and the particulars o
this feat Of submarine blasting will be inter
esting to our readers.
A careful survey of the rock was made a
the outset in order to ascertain the irregu
larities Of its surface. This being done
and plans being drawn, a Golfer dam va:
constructed around q portion of the rock "a
be removed, and moored By means Of A
scow loaded down with heavy stones.
The water was stopped from entering the
dam by sand bags placed about its base,
and an iron turret was erected within Il.
This turret was then sunk three feet into
the rock and cemente1 fast. A platform
6hy-six feet long and twenty feet vide was
then erected, and an engine and hosting
apparatus placed thereon, together with q
building in which to lodge the workmen and
prepare their meals.
The plan Of excavation was to scoop out
the interior Of the rock, leaving an exter-
nal she'll Of sufficient thickness to resist the
pressure Of the surrounding and suDerin-
cumbent water. and finally to shatter and
scatter the shell by blasting The thick
ness OF The she'll was about six feet.
Pillars Of rock were left to sustain the
shell. and when these were removed thew
we're placed by timber supports. The
space excavated measured in The clear l4O
BY 80 feet, and it is estimated that aboui
40, 600 cubic feet Of stone were taken out,
The shape of the surface Of the rock was
nearly oval, but for distance of abont l2O
feet it sloped very little. The hight Of the
highest pillar inside was 20 feet. and the
lowest four feet. The stone was a porous
sandstone. When struck with hammer
1t fell to pieces readily, and revealed series
of seams running through it. There was
no mixture Of slate or granite, or any Of the
harder kinds ofstone in it
Of the twenty-three tons of powder used.
about half was contained in English ale
casks, double coated with heavy pitch
varnish inside and outside 30 as to Be water.
proof. The other half of the powder was IN
seven boiler tanks Of wrought iron, firmly
bolted, the largest measuring eight feet in
length and two in diameter. The barrel,
were placed close to the side of the excaya
ton, near the junction Of the arch or roo
with the floor, 50 as to blow away the arcl
from the loweet point of the excavation
reached. They were placed resting o.
their sides. The seven boilers were laic
through the centre Of the chamber. tb,
largest in the middle, where the roof wa
highest This disposition was made /,
equalize the force on each part of the rock
A perforated piece Of gaspipe, two and
half feet length, charged With fine gunpow
der. ran into each barrel from the end
with piece six feet long into the boilers
charged in the same way. These different
tubes were connected with insulated elec
trio wires, which passed from one barrel tC
another, the end in each tube consisting Of
O fulminating cartridge.
The insulated electric wires connecting
the barrels we're incased in gutta-percha.
When the powder was arranged in the ex-
cavation, and the connections made secure,
this wire was drawn up through tube in
the shaft, and placed on board bark stu
ated about one thousand feet from the rock.
Here it was connected with an electric bat.
terry. The coferdam was then removed.
and the water permitted to Gil up the ex-
cavation, and 50 act as tamping.
IL being understood that the blast would
be fired On the 2Sd Of April, very larr,
ooncourss Of people gathered TO witness &.
Everything appears to have worked prO-