The Indiana State sentinel. [volume] (Indianapolis) 1868-1895, 1876-01-05
ruNNEL1Na THE CHANNEL
THE PROPOSED PLAN.

The Paris correspondent of the Philadel- |
mia Bulletin writes: II is not only with
the suez canal that the name of NJ. de Les
seps is connected, and has been brought at
this moment prominently before the pub
lie. With great propriety the same individ-
ual who achieved the above named gigantic
work was deputed, on Monday last, to lay
before the Academy of Science, at its Gus
tOmary sitting, the deeply interesting re-
port OF NJ. Lavsllsy upon the progress max
ing and tbs results hitherto obtained in an-
other undertaking of even grester magni-
tude aad more peril 1 refer TO the prellmi-
nary experiments and Investigations Whicn
have been going on throughout tie past
summer, on both sides OF the chan
mel WITH q view TO the construction OF
the submarine tunnel between this country
and Greas Britain. AS the Suez canal que
ton has SONS what subsidized in interest, and
is not perhaps likely to offer any new phase
until the mat or comes TO be detated In tie
British parliament, shall take the opportH-
nifty of transferring your readers attention
from the passage over, or rather, perhaps,
through, the sands OF Egypt TO that under
the ssa which divides France from England,
and give short resume OF NJ. Lavalley's
document respecting it. NJ. Lavslley 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 tun-
mel Itself is, in the main, that OF Sir John
Harkshaw, which proposes 10 make the tun-
mel start from point of the French coast
between Calais and little fishing village
called SaDgatte, and strike the opposite
shore in the bay of st. Margaret, some five
miles east OF Dover. Cbe entire length
FROM SHORE TO SHORE
will be about twenty-five miles. But the
functions, on both sides, with the French
Northern line and the English, Chatham
and Dover and Southeastern lines, respect
lively, viii be very long. In mid channel
the tunnel will be about three hundred and
fifty feet below the surface OF the sas at low
water, and two hundred feet below the bot
tom OF the sea itself. To attain this great
depth, the line, on quitting the French
Northern railway, will enter, at slight
gradient, first cutting, and then, plungiBg
gradually into q tunnel, will find itself
already at depth of some two hundred feet
below the soil before it enters beneath the
water. Continuing still to descend for some
three or four miles further on with the dip
of the sea ITSELF, the tunnel will then
slightly trend upward again until it reaches
the middle of the strait, the object of this
slope being to obtain drainage for the
in6ltratioD, which will thus bs carried
hack, first TO the point where the slope
to reservoir at the shore,
where it will be pumped out. The
track of the other half of the lire, on the
British side. will be precisely SINH az to that
of the French. The one great difficulty to
be overcome, or rather the point to be de-
fined in making the tunnel and deciding at
once upon its practicaOility and its position,
was to discover, with certainty, a suitable
and ssfe medium through which to bore it.
The boring itself was only a secondary con-
I'D f0r mil n hn In
cry, 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 coincide very much as the
veins of wood would be found to do in a
tree out of which large notch had been
cut, showing the grain at either extremity.
Tbess strata have been found to consist
principally of three kinds, chalk and flint
mixed, white chalk and gray chalk. Now,
both the two first mentioned strata are
found liable to be
TRAvRRsED BY FIssUREs OR CREvIcEs,
through which the sea might pour in; but
the gray chalk is known to be absolutely
impermeable. The first thing, therefore
was to find spot where this stratum of gray
chalk extends from coast to coast in suffi
Gent dimensio TO receive the proposed
tunnel. A thickness of 200 feet above th,
roof OF the tunnel was deemed ample Il
guarantee the work against all dsngeroui
utilization; and a stratum of such proper
tons was found to exist between the twi
points OF the coasts above mentioned. Tn,
bottsm OF the sea there is composed of whit
chalk, and about two hundred feet below
is found the required gray chalk. There re
NAMED, therefore, only one other fact to b.
investigated and decided; but that was of
very important and difficult character. An,
one who has lived in a mining district mus
have heard of what miners call "tTouble;
that is, sudden break in the seam OF coal
caused by some internal commotion
by which the continuity of tn
seam is suddenly cut of, and the two edges
thrown up or down to a considerable dis
lance from each other. The same thinl
might happen In seam of gray chalk, an,
if so, would present formidable IL no
even an insuperable obstacle to a safe pas
sage through il, of the proposed tunnel
1t is mainly, therefore, with q view to guar
against the risk of falling in with such Al
obstacle, that Il g toilsome and minute pre-
Hminary Investigations of last summe
have been carried. The great object to b
ascertained was whether any sue
"trouble" as that above mentioned did &C
tually occur in the line of the stratum c
gray chalk, which, it was found, extende
in one shape or another from coast t
coast, az the point fixed upon; to se
whether any sudden rises or iallings, bule
ings out or sinkings in alone the line ind
Gated its existence. To effect this IL wa
necessary to inspect minutely the bottom
of the sea from point TO point by sound
iDgs, to make sure that the level RENAME
UNBRoREN AND UNDIsTURBED.
This operation was complicated by th
difficulty of having to allow for the differer
depths of water which vary so CONSTANT
with the tide in the channel, and made
new calculation necessary everv nuartar =
an hour, TO be sure thst the bottom la
evenly and did not bulge out or sink in. n
less than So soundiDgs were made f.
this purpose between the 10th of Angus
and the 25th OF September. AS far as
present aseertained, the result hes prove
that the strata il even and unbroken up
the French cosst, with the exception OF
rs--L-k a. 4,