New-York tribune., 1870-04-25
BLOSSOM ROCK.
THE GREAT BLAST IN SAN FRANCISCO HARBOR-
TwENTY-THREE TUNS OF POWDER EXPLODED
FULL PARTICULARS OF THE EXCAVATION
AND DETAILS OF THE PLAN NOVEL

TWENTY THREE TUNS OF POWDER EXPLODED
PULL PARTICULARS OF THE EXCAVATION
AND DETAILS OF THE PLAN-A NOVEL
ENGINEERING WORK.
SAN FRANCISCO, April 23.-BlossOm Rock, the
most dangerous obstruction in this harbor blown up
to-day o'clock. Twenty-three tuns OF powder were
used. When this immense quantity of powder was
touched OFF, the water apparently 100 feet in diameter,
was thrown the hight OF about 100 feet the center
being filed with smoke and sOnes-the latter going lar
above the water Between $4,000 and CO0O0 people wit
messed the explosion 1t scarcely perceptble in
the city; only q deep thud accompanied the blast.
Col. Van Schmidt Civil Engineer, began the work
completed by this explosion between four and I'VE
months ago. The adopted for its removal are said
TO be entirely submarine blasting, and the en-
gneer undertook the experiment at much risk His idea
the utter annihaton Of the rock when put before
the public left little doubt that il might prove success
full though many doubted that the could he done.
at low tide and situated where the water rolled over III III
powerful swelis and with great force.
The irst work done under Col Won schmidts plan was
to make careful survey OF the rock ascertain wheret
excayation afterward accomplished sufdcien space
might remain TO resist the Of the water This
carefully done and from 1t plans were drawn OF the
The work to construct vatertight cof
ter-dam on the rock rock and sE ar around that part
sunk. This was found TO lie very difficult.
The cGrdam S was so%d put in its st place ScS and then
tuns OF stones thrown. The dam lined
| around
the water and when this was complete an iron turret
was placed inside of it, This turret was lmbeded or
mented in its place platform was then erected on the
rock, sc feet In length and about 70 in width On one
placed, and at the other end shanty was erected
containing six sleeping apartments and Kitchen which
sinking of the main shaft was then begun When the
shaft had reached certain depth small cylinder was
placed inside the original trret which made the hoist
| ing OF the ballast from below more convenient.
The object was 10 scoop out the center of the rock
highest point to the bottom 25 feet and leaving crust
Of about feet thick 10 resist the pressure Of
stratum TO be blown up by powder when the remainder
OF the work inside had been completed To do this how
ever not only difficult but perOns. As the eXcava-
became larger the crust OF rock left standing would
naturally become weaker and likely to cave in To pre-
vent this pillars Of rock LETT standing at short
intervals from each other until the limits OF six
feet was everywhere reached Thent became necessary
rights heavy timbers set thcky around the
moved except the two main Ones which stood at either
side Of the shaft These left to the last moment
y so feet and estimated that about 40OO cubic feet
OF stone were taken out The shape OF the surface OF the
nearly oval but for distance OF about 100 feet
ii sOped very little The hight OF the highest pillar in
side 20 feet and the lowest feet The stone was
porous sandstone When struck with a 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 kind Of stone in IT, from which seemed
evident that ii would blast well.
The plan Of explosion was follows Of the % tuns
Of powder used, about half contained in English
ale casks double coated with heavy pitch varnish In.
side and outside 10 be water proof The other half
OF the powder in boiler tanks Of wrought iron,
firmly boted the largest measuring eight feet in length
and two in diameter The barrels placed close to the
side Of the excavation the junction OF the arch or
roof with the floor TO blow away the arch from the
lowest point OF excavation reached They placed
| resting their sides. Tie seven boilers were laid
through the center Of the chamber the largest in the
middle where the roof highest. This disposition
made 10 equaze the force each part Of the rock
perforated piece Of gpipe, q feet in length charged
with fine gunpOwder into each barrel from the end,
and piece six feet long into the boilers charged in the
way These different tubes were connected with in
suated electric wires which passed from barrel 10
another the end in each tube consisting Of Illuminating
cartridge.
The insulated electric wires connecting the barrels
were incased in gutta- percha. When the powder was
arranged the and the connections made
cure this wire drawn through tube In the shaft,
and placed board bark situated about 1900 feet from
the rock Here il connected with electric battery
The cOfferdam then removed, and the water per
mtted fill up the excavation, and so act as laplng
No f survey or soundings yet been made, but IL
is believed that the explosion has been entirely sue
cessful.