Evening star. [volume] (Washington, D.C.) 1854-1972, 1876-05-06
ROCK BLASTING UNDER WATER.
Divers. Diamond Drills and Nitro
gIyeePfne.


The work of removing a bed Of rock which
has for q long time been a dangerous OBJ
struction In the channel ofthe river opposite
the foot OF Potomac street, GEORGETOWN roy
In progress, has beer briefly men toned In
TIE STAR. The processes used are novel In
this region, and deserve a more extended
notice. The work is being done by the ma
uonal government. and il under the super
vision Of Col. 3. 7. Albert, and In the i'm
mediate charge Of z. G. Hall, esq, of Rich-
mOnd.
THE LEDGE OF ROCK,
which isbeiDg removed is q veia OF bastard,
granite, mixed with quartz and mica, aud
Is about 60 feet In length and As in width.
only about feet below the surface OF the
water. One bed OF rock which was 10 or II
feet below low water marx is now II or 10
feet below. The existence OF this rock In
mid-channel was owing to Its hardness, and
while the softer blue gneiss was worn and
washed away BY the action OF the water,
IN many places the soft streaks in the rock
have been washed out leaving deep holes and
large caverns in the granite.
THE PROCESS.
In order TO remove these rocks the first
thin g that is done is to find out where they
are, their height and extent, sc, which is
done by sounding with long poles. The diver
men soes down and adjusts the drills at
drills are worked by two rotary engines upon
platform which Is lowered and raised with
the tide The drills are cy lindrical, made of
steel, with rough diamonds inserted in the
end. They cut into the hard rock at the rate
of foot an hour, leaving inside the drill q
clean core of cylindrical stone, which is
withdrawn and the charge inserted. These
diamond drills are worth from 800 to $500
They make from SEQ TO 600 revolutions per
minute.
BLASTING.
AFTER the core is taken out the diver In
serts in the hole a tin tube filled with nitro.
ycerine, which is discharged by means of
al mt hoN Tl,ar. - 10
be done, the entire apparatus is moved at
convenient distance, to prevent any posi-
bic damage. On account OF the heavy
pressure of water, 20 rocks have as yet
been thrown TO the surface, but the water is
throw n TO a considerable height. In con-
nection with the drilling engines there are
three pumps which force water down the
cylinder upon which the drill works to keep
the diamonds cool and to force up the dust
The diamonds never wear, but the steel I'm
which they ere placed does, and sometimes
the diamonds are thus lost. After the rocks
are blasted, the diver goes down, fastens a
chain around the detached portions, and they
are brought up by seven horse power en-
gine. Upon The top OF the rock a propeller
wing was found, which was lost, of course,
by some steamer striking the rock; part OF
an anchor was also found at the same place.
THE DIVERS.
Two drivers are employed, who work five
hours day each and receive 80 per day.
They saw the sensation when one goes down
for the first time is fearful, and q "fellow
thought Of for q long time" Sometimes
too, blood spurts out from the nose and ears
sharp pain like the ear ache goes through
the head; but like everything else, you soon
get used to IL. Their aTmor Is unpleasantly
suggestive of burial case, and has glass
about three quarters of the way around the
top through which the diver can see all
about him. The divers are sometimes under
water two or three hours at time and come
up with bleeding hands from contact with
the sharp corners of the rocks. Their shoes
are clogged with lead to keep them down.
There is "life-line' attached to them held
10y man above, and fresh air is regularly
supplied TO them by a pump. The locality
OF The diver can be seen by the bubbles
caused by The air forced out of his rubber
"shell,o