The Bloomfield times. [volume] (New Bloomfield, Pa.) 1867-187?, 1871-02-21
SCIENTIFIC READING.
THE MOUNT GEMS TUNNEL.

d IN lOOO NAlOlEON CONSTRUCTED
l. road over the pass of Mount Gents,
at an expense of 7,000,000f, which,
at the time, was regarded at great en-
gineering triumph. 1t was eighteen
feet wide and thirty miles long, and af-
forded fine road-bed, though passing
over an elevation amile higher than the
level of the surrounding country 1t
served for many years as the only high
way from France to Italy. Subsequent
ly, after the age of railroad engineering
and tunnelling was fully inaugurated, the
idea was broached of going under the
mountain instead of over it. Examin-
alton proved that the little stream of the
Dora, on the Italian side, approached, at
one point, to within less than eight miles
Of the Arc on the French side; and the
valleys of these two streams afforded ex-
cellent railroad routes, down to the plains
of Italy and France. Between the points
however, where the rivers approached
nearest to each other, lowered three lofty
mountain peaks, the highest more than
two miles above the level of the sea- OF
course, tunnel, if attempted through
such range, could not be excavated, as
is usual, by shafts sunk at intermediate
places between the two extremities. Such
u shaft would cost more than the tunnel
itself, besides being useless, when done,
on account Of the immense elevation. The
excavation could be made only from the
two ends, and by any process then in use,
its completion could not be hoped for
within less than forty to fifty years This
was discouraging prospect indeed, yet
so earnestly did the advocates of the
work urge it, that, with the guarantee of
Governmental aid, it was commenced on
the Italian side in 1857.
The work for the first four years was
done entirely by hand-drills and blasting
with powder But, meantime, engineers
and inventors were anxiously endeavor-
ing to bring into use more effectual means.
Steam could not be employed as power
for drilling, for, when the tunnel had
progressed little way, there was not air
to feed the fires, it being difficult to force
in amid the smoke and gasses of the
blasting, enough air even for the work.
men to breathe. In this difficulty it was
seen that if any apparatus could be con-
trived to use compressed air as motive
power, it would meet all the needs of rap
id motion for the drills, ventilation for
the workmen, an atmosphere to sustain
the requisite lights. Experiment accord
ingly took this direction, and after many
discouraging failures, the required ma
chine was produced. The streams on
either side of the mountains afforded the
needed power to drive immense air
pumps, which compressed air to one-sixth
its ordinary bulk, and drove it into reser-
voirs From these it was taken in tubes
into the tunnel, and, when allowed to es-
cape, afforded all the power needed to
draw the cars and drill the rocks, and
then drove away in gusts the smoke of
the blasting, and gave the workmen the
clear atmosphere they needed for their
life and comfort.
The drilling machine itself was fixed
on an iron car, which was moved by air
power backward and forward upon rails,
as need might require. Each machine
had ten perforators these were struck by
force equal to 200 pounds, turned
partly around and then Withdrawn Two
hundred of these blows were given each
drill per minute. After about 90 holes,
3 feet in depth, and or inches in di-
amcter, converging little toward each
other, were drilled, they were charged
tamped, and the machine Withdrawn by
the work men hphind woodan doora which
had been made for their protection. The
slow match was then applied and the
charge fired. This process was then re-
peated, while other workmen were en-
gagged in picking up and removing the
debris upon their air drawn cars. And
so the work went on, day and night, sew
en- days in the week, and tifty-two weeks
in the year, till now we find the work
of more than forty years Of hand labor
has been compressed into about eight of
this machine work. About $500 work
men have been employed, those within
the tunnel working in gangs of about
three hundred and fifty each relieved
three times in the twenty four hours,
eighteen hours being given to labor and
sixteen to rest. Common laborers re-
ceiyed three francs, day; skilled, five.
At first powder only was used for blast
ing; afterward, gun-cotton; and, finally
nitro glycerine.
The full length of the tunnel is 7 3-5
miles while its average height is 20 feet
and its width rs feet