Evening star., 1925-08-23
lite Nammoth Concrete Tile, re ady for buriat

ment inspector, keeps tab on the oper-
ations of each shift to see that the
work is done exactly as stipulated by
the contract. Under present condi-
tions about 10 feet of tunnelway is
being cut daily. -'
Ordinarily two shots are fired. Each
shot is responsible for feet of rock
ribbed passageway. Usually 16 holes
are bored with the compressed-ai air
rock drills. Suppose that these holes
are each feet deep. They are
charged with 33 pounds of dynamite.
The miners retire about 400 feet from
the heading to be shot. The charge
is then fired by electricity. Some
times the rock flies 200 feet down the
tunnel from the scene of explosion
The detonation Is deafening.
Residents of Washington know prac-
tically nothing about these tunneling
operations in that elevated district
above Wisconsin avenue. Hence it
was not at all surprising one fine
Summer day when an expensive auto
mobile passed that way to have the
driver stop the machine and descend
with his two lady companions to
gather wild flowers in the neighboring
meadow. Fate placed the choicest
flowers directly above the subter-
ranean digging enterprise. The trio
of nature lovers, all bending over and
picking Sweet-scented blooms, of a
sudden arose, as though by order,
looked inquiringly at one another, and
then turned and fed precipitately to
the motor car. Pell.mell style, they
on the starter with alacrity. The car
sped away as though pursued by sa-
tanic demons.
If you know anything about the vi
brations produced by the discharge of
a powerful underground dynamite
shot you will understand Immediately
what caused the wild-flower pickers to
fee. 1t so happened that 40 pounds
of explosive were discharged exactly
35 feet below where they were stand
ing A very perceptibfe tremor re-
suited Probably the blossom -ga tn.
erers imagined that n California earth
quake had gone astray and centralized
its energies close to the City of Presi
dents. Anyway, they decided that i'm
mediate flight was the best prescrip-
tion of discretion for such case. So
they fled.
r 1NORTHODOX explosions In Wash
- 'ington's deep.seated tunnelway
have to be explained. The dangers of
cave-in and disaster are as dire as
though the rock-lined passa geway
were 100 times as deep. Loose rock.
detached from its anchorage by the
concurrent vibrations and conclusions
of daily explosions and further under
mined by soil water action is liable to
fall, swift as the bolts of Jeve, and
MAIN or kill the miners who chance
to be below A cave-in would block
the tunnel and shut off access to the
shaft 1t would shut off the ventilat-
ing air supply. The imprisoned men
caught in such a catastrophe might
die before succor could reach them.
That Is why all irregular noises,
flames or other agents Of potential
explosion have to be accounted for.
Our photographer used an extra
heavy charge of flash powder when he
exposed the first negative under
ground. The miner who had charge
Of firing all the shots was at the op-
posite end Of the level, and did not
know that picture-taking was in prog
ress. All of a sudden we heard the
splashing and fioundering steps of a
man who was in desperate hurry
The sprinter, incumbered by heavy
hip boots and the knee-deep water,
wallowed our way. He sounded like
the start of a dozen thoroughbreds
sent away from the barrier at Pim-
lico when track conditions were super