The Cincinnati daily star. [volume] ([Cincinnati, Ohio]) 1875-1880, 1876-01-04
nNeL AND AND FRANCE.

| the name of NJ. de Lessers is connected,
and has been brought at this moment,
prominently before the public. With
great propriety, the same individual
who achieved the above-named gigantic
work was deputed, on Monday last, to
lay before the Academy of Sciences, at
its customary sitting, the deeply inter-
esting report of NJ. Lavalley upon th e
progress making and the results hither-
to obtained in another undertaking of
even greater magnitude and more peril
| Ireter to the preliminary experiments
and Investigations which have been
going on throughout the past summer,
on both sides of the Channel, with view
to the construction of the Submarine
Tunnel between this country and Great
Britain. AS the Suez Canal question
has somewhat subsidized in interest, and
is not perhaps likely to offer any new
phase until the matter comes to be de-
bated in the British Parliament, ] shall
take the opportunity OF transferring your
readers attention from the passage over,
or rather, perhaps, through the sands of
| Egypt, to that under the sea which di-
yides France from England, and give
short resume OF NJ. LaYalley's document
respecting it. M. Lavalley is, need
hardly say, the engineer under whose
inspection the preliminary operations
are being carried On on the part OF the
French projectors.
The plan adopted for the tunnel itself
is, in the main, that OF Sir John Hawk
shaw, which proposes to make the tun-
mel start from point of the French
coast between Calais and little fishing
village called Sangate, and strike the op-
posite shores in the Bay OF st. Marga-
ret, some miles east Of Dover. The en-
tire length from shore to shore will be
about % miles. But the functions on
both sides, with the French Northern
Line and the English Chatham and Do
YER and Southeastern Lines respect
lively, will be very long.
In mid-channel the tunnel will be about
$50 feet below the surface of the sea at
low water, and 200 feet below the bottom
of the sea itself. 10 attain this great
depth. the line, on quitting the French
Northern Railway, will enter, at slight
gradient, first a cutting, and then, plung-
ing gradually into tunnel, will find it.
self already at a depth OF some 200 feet
below the soil before it enters beneath
!, the water.
II Continuing still to descend for some
three or four miles further ON with the
dip of the sea itself, the tunnel will then
lslightly trend upward again until it
lreaches the middle of the Strait, the OBJ
Iject of this slope being to obtain drain
age for the intiltration, which will thus
be carried back first to the point where
the slope began, and thence bya conduit
to reservoir at the shore, where it will
be pumped out. The track of the other
half of the line, on the British side, will
be precisely similar to that of the French.
The one great difficulty to be overcome,
or rather the point to be defined in max
/ ing the tunnel and deciding at once upon
it's practicaDility and its position, was to
discover, with certainty, a suitable and
safe medium through which to bore it.
The boring itself was only secondary
consideration; for, with the Brunton
machinery, almost anything IN that way
can now be accomplished. With this
view, the cliffs on both sides have been
carefully examined and compared at the
points of disruption, and found to coin
eide very much as the veins of wood
would be found to do in tree out of
which large knot had been cut, show
ing the grain at either extremity,
These strata have been found to con-
sist principally OF three kinds: Chalk
and flint mixed, white chalk, and gray
chalk. Now, both the two trst-mer-
toned strata are found liable to be ira.
yersed by assures or crevices through
which the sea might pour in; but the
| gray chalk Is known to be absolutely
| impenetrable. The first thing, therefore.
| was to find a spot where this stratum Of
| gray chalk extends from coast to coast
lin sufficient dimensions to receive the
proposed tunnel.
| A thickness of 200 feet above the root
of the tunnel was deemed ample to
guarantee the work against all danger.
Gus infiltration; and stratum of such
proportions was found to exist between
The two points of the coasts above men,
toned. The bottom of the sea there is
composed OF white chalk, and, about 30
/ feet below, is found the required gray
chalk.
There remained, therefore, only one
+ other fact to be investigated and decid.
4 ed; but that was OF very important and
difficult character. Any one who has
lived in mining district must have
heard OF what miners call a "trouble :"
that is, a sudden break in a seam of coal,
caused by some internal commotion, by
which the continuity of the seam is sud-
denly cut of, and the two edges thrown
up or down to a considerable distance
from each other. The same thing might
happen in a seam OF gray chalk; and, ii
ISo, W0uld present a formidable, II not
even an insuperable obstacle to safe
lpassage through il of the proposed tun-
mel. 1t is mainly, therefore, with O
view to guard against the risk of falling
lin with such an obstacle, that the toil-
some and minute preliminary inves tiga-
tions OF last summer have been carried
Ion.
The great object to be ascertained was
whether any such ''trouble" as that
aforementioned did actually occur in
the line Of stratum of gray chalk which,
it was found, extended in one shape or
another, from coast to coast, at the
point fixed upon; to see whether any
Isinkings in along the line, indicated its
lexistenee. TO effect this it was neces-
sary to inspect minutely the bottom OF
1.-THE sea, from point to point,
Iby soundings, to make sure that