Evening star. [volume] (Washington, D.C.) 1854-1972, 1885-10-02
Ready tO Blow Up Flood Rock.
EXPECTED EFFECTS OF THE ExProsioy.

From the New York Tribune, October LIST
To passengers on the big sound steamers that
carefully pick their way through the whirling
currents of He'll Gate every night and morning,
there is little change noticeable i'm the works
on Flood Rock. The same skeleton OF smoky
oily timber raises its angular frame work
against the background OF the charity hotels ON
Ward island; the same endless stream of dirty
water flows from the tireless pumps and the
same solitary workman stands on the dump
and gaZes at the passing steamer. But down
under that desolate island and out under the
foaming current, many men, and machinery
nn sSav ahrnngb a,d ILL.,, io w oesn aeiv
ing behind them a legacy of ynamite that In o
fraction OF a second will make the work Of
years visible. Lieut.. Derby, who has had Inn
mediate charge OF the work. the elimination oe
which will occur within a week, was found by .
Tribune reporter yesterday, in the midst of saw
dust and dynamite, overseeing the preparation
of the last of the explosives which are To knock
the bottom from under Flood Rock.
"There Is wrong impression" said he, in
speaking OF the coming explosion ain regard 10
the state OF affairs Immediately after the firing
People seem to think that the whole thing will
cave i'm and there will be Do feet of water all
about here from that moment ON. The truth Is
that there will be on an average four feet less
water at every point than there is ut present.
1t was the old idea to undermine and then;
pnlling the prop out from under the bottom,
let it fall i'm and lie there. With the improve
ment OF dredging apparatus We find IL cheaper
TO do just as little tunneling will suffice to
thoroughly distribute the explosives. The ex-
which can be handled. In this case expecr
to lift the whole bed OF rock right up from it's
resting place. There will then be a mass OF
broken stone that will lie four feet higher than
the solid rock at present This will be picked
up by dredges and dropped i'm the deep hole
north of Blackwell's island, where tons and
tons of rock have been dumped and there 10
still 30 feet of water. In year or so. IL the
work is not checked, il will all be cleared up
and there will be 20 feet Of water where Flood
"will not the report be much louder than
that when Hallets reef was blown ups" asked
"Yes, probably, because part Of the rock ID
out of water while the other was entirely sub
Hnnd ne pieces VIII ny also % pS S M,
TO come within a radius of that length, and we
shall explode the mine from point ON the As
toria shore beyond that limit. No Injurious
effects are expected, but IL is always wei 20 be
on the safe side. 1t would be much better for
a man to take down his French pier glass and
lay it on the moor a dozen times, than 20 have
II shaken down once"
"What will be the effect on the currents7'
"The immediate effect will be TO make them
worse than at present. Amer the fragments Of
rock are all cleared away they will be much inn
proved They will still be strong and TO q certain
extent conflicting, but not so much SO as at pres
ent The removal OF the rock will be begun Inn
mediately after the explosion, as we have about
81 $4,000 on hand for that purpose"
SHOW does this compare In size with previous
well, il win be four or five times larger than
anything else of the kind"
The original estimate for the work OF I'm.
proving He'll Gate channel was IS, 138, 100. Up
expended. The work on Flood Rock alone
amounts to q round million. The total cost OF
removing the broken rock after the explosion
is estimated at 100000. The dynamite cart
ridges, the preparation OF which has been
Lieut. Derbys special care for several months,
circumference and several feet long. They com
tain an explosive compound known as rack-or
rock and some pure dynamite Of the No 1
grade They will be exploded I'm part directly I
by an electric current and partly by concus-
sion. The holes In which they are placed point
upward at an angle OF forty five degrees and are
nine feet deep. AS the initial explosion occurs
at The mouth Of the hole, the tendency will be
TO drive the cartridges still deeper into the
motion that will be produced by the stimuli
taneous liberation Of the enormous force
chained up In several hundred thousand
pounds Of these high explosives can scarcely
be conceived even BY the most able-bodied Inn
aRination.