Year: 1870

Z


BLOSSOM ROCK,


The Great Blast in san Francisco
aarbOr -ATentY-thrce Tons OF
Powder Exploded.


SAN FRANCIsCo, April %,
Blossom Rock, the most dangerous
obstruction in this harbor, was


blown up to day at two o'clock.
Twenty-three tons Of powder were


used. When this immense quantity
of powder.was touched of, the water
apparently one hundred feet in dia-
meter, was thrown to the hight OF


about one hundred feet the center
being filed with smoke and stones
the latter going far above the wat


er. Between 10000 and 10000 per-
sons witnessed the explosion. It


was scarcely preceptible in the city;


only a deep thud accompanied the


blast. Col Won Schmidt, civil engi-


noer, began the work completed by


this explosion between four and five


months age. The means adopted
for its removal are said to be entirely


novel in submarine blasting, and the
! iengineer undertook the experiment
, at much risk. His idea for the utter
annihilation of the rock, when put
I before the public, left little doubt
/ that it might prove successful,
though many doubted that the work
could be done. Blossom Poek was


six feet feet below the surface, of
the water, at low tide, and situated
where the water rolled over it in
| powerful swellsand with great force.


The first work done under the Col
Won Schmidt's plan was to make a


careful survey of the rock, ascertain


where it dipped in and where it pro
ljected, so that the work Of excava-
ton afterward accomplished sufici-


ent space might remain to resist the
pressure of the water. This was care
! fully done, andfrom it plans were
drawn Of the rock. The next work
was to construct a water-tight Golfer
dam on the rock, and around that
part Of it through which the shaft
was to be sunk. This was found to
be very difficult. The cofer-dam
was put in its place, and then q scow
was built around it, into which about
two hundred and fifty tons of stones
were thrown. The dam was lined
around with bags of sand to more
efectually keep out the water. and
when this was completed an iron tUr-
mt was imbedded or sunk in the
rock a distance Of three feet and
closely cemented in its place. A
platform was then erected on the
rock ffty-six feet in length, and
about twenty in width. On one end
of this an engine and a complete
hosting apparatus was placed. and
at the other end q shanty was cree
ted containing six sleeping apart
ments and a kitchen which was also
used as an eating room by the work
man. The sinking of the main shaft
was then begun. When the shaft
had reached certain depth small
cylinder was placed inside the origi-
nal turret, which made the hosting
of the ballast from below more con-
yenient,


The OBJECT was to scoop out the
center of the rock, producing cayi-
ty inside, measuring in the clear,
from the highest point to the bot
tom twenty-five feet, and leaving a
crust or stratum of about six feet
thick to resist the pressure Of the
water while the work was in progress
this crust orstratum to be blown up
by powder when the remainder Of
the work inside had been completed.
To do this, however, was not only
but perilous, As the exca-
vation became larger, the crust of
rock left standing would naturally
become weaker and likely to cave
in. To prevent this, pillars Of rock
were left standing at short intervals
from each other, until the limits Of
six feet was everywhere reached.
Then it became necessary to remove
those pillars. Before this was done
uprights and heavy timbeTs were
set thickly around the cavity to sup
ply their place. All the pillars were
then removed except the two main
ones, which stood at either side Of
the shaft. These were left to the
last moment poss bic. The place
excavated measured in the clear one
hundred and forty-hve feet, and it
is estimated that about 10000 cubic
feet Of stone were taken out. The
shape of the surface of the rock was
nearly oval, but for q distance Of
about one hundred and twenty feet
it sloped very little. The hight Of
the highest pillar inside was twenty
nine feet and the lowest four feet.
The stone was a porous sandstone.
When struck with hammer it fell
to pieces readily, and revealed
series of seams running through 1t.
There was no mixture Of slate or
granite, or any of the harder kind OF
stone in it. from which it seemed ev-
ident that it would blast well,


The plan of explosion was as fol
lows: OF the tweuty-three tons of
powder used, about half was con
tanned in English ale casks, double
coated with heavy pitch varnish
inside, and outside, so as to be wat
er-proof. The other half OF the pow
der was in seven boiler tanks Of
wrought iron, firmly bolted, the larg
est measuring eight feet in length
and two in diameter, The barrels
we're placed close to the side of the