The Sun.
London, England, 1857-11-20 00:00:00

TUNNEL BETWREN ENGLAND AND
ERA C

The writers on scientific subjects in the Paris
press have formed themselves, under the name of
" Cords de la Press° Scientifique," into a society,
which, amongst other things, proposes to hold
weekly meetings, at which the authors of new
discoveries of inventions will he admitted to ex-
plain their views, and scientific subjects will be
discussed. The first meeting has just been held,
when M. Thome de Gamohd, the projector of the
submarine tunnel between England and France,
communicated the details of this astounding enter-
prise, and the principles on which it is founded,
The first idea of this tunnel is due to the engineer
Mathieu, who conceived it sixty years ago. M.
Thome took it up again as far beck as 1833, while
engaged in a series of geological investigations for
another purpose. It was then he was struck with
the similarity of the soil on both sides of the chan-
nel ; and, upon closer examination, he found that
the chalky deposit, which is the most striking fea-
ture of the English and French coasts, constituted
a kind of convex lens, fitting in a concave one of
jurassic formation, that is, composed of the argil-
laceous and stony deposits of a sea which formerly
covered large tracts of the western part of Europe.
This jurassic soil, seems, therefore, to be continued
under the sea ; the extremities of the submarine
curve which it forms are apparent on the surface
at a place called Marquise, in France, situated be-
tween Boulogne and Calais, and at Oxford, in
England. Now it was clear that if the inclination
of this curve was the same in both countries it
might be practicable to cut a tunnel following its
direction. But here M. Thome met with a diffi-
culty which at first sight appeared insurmount-
able ; the curve which in England had an inclina-
tion of 3 per 1,000, showed one of 7 per 1,000 in
France. This circumstance induced M. Thome to
abandon his project, until, in 1851, it struck him
that the jurassic basin was itself contained in an
oolitic basin, and from soundings taken and infor-
mation derived from M. Keller, an engineer
attached to the navy department of 2 France, it was
at length ascertained beyond a doubt, that if, as
resultd from the difference of inclination, the ju-
rassic stratum had been broken by some subma-
rine convulsion, the oolitic stratum had not.
About two-fifths of this stratum consist of the
kind of stone with which the French cathedrals
are built, and of the sandstone-grit used for pav-
ing ; the remainder comprises argillaceous earths
of three different ages, viz., a zone of Oxford clay,
the vast zone of Kimmeridge clay, 50 metres thick,
and .a zone of weald-clay which on the English side
is uppermost, the 2d being in contact with the sea
for a considerable space. The tunnel is designed in
a direct line from Cape Grinez in France to Eest-
ware Point in England crossing the Varne Bank
in the middle of the Channel. Here comes the
most stupendous part of the project. Let the
reader imagine the surface of this bank raised
above the level of the sea, and the island thus
_ormed at one of its extremities, to be hollowed
out, or pierced with an immense elliptical shaft,
200 metres in length by 100 iu breadth ; the base
of this hollow tower forming a resting-place for the
trains, whence a spiral road winding its way up
along the walls of the tower leads to the top, where
a large port is formed, called the "Verne Star,"
with a light-house, dwellings for officials, and
every other convenience. Here ships may receive
cargoes direct from the tunnel or unload their mer-
chandise and send it down. This port, however,
is not considered a conditio sine qua non in M.
Thorne's project, and may be studied apart. The
tunnel itself is a concave line with an inclination
not exceeding 5 per 1,000 under the sea ; but the
subterranean galleries leading to the tunnel have
an inclination of 7 per 1,000. The gallery on
the English side commences at Dover, and is
5,500 metres (31 miles) in length; that on the
French side is 8,800 (fel- miles) long, extending
from the Grinez station to Marquise, where it
meets branches of the Paris and Boulogne, and
Belgian railways. In case of war occurring
water can be let into the tunnel, and ren-
dered temporarily unserviceable. For the execu-
ton of the tunnel the modus operandi proposed
by the projector is as follows :—Exclusive of o the _
Varne Star, 13 artificial islands more are
made in the channel along the projected line. These
islands ese
b
islands are to be composed of rock cemented with
clay,
rt
ct
w
the e
r 220 metros
length, the altitude 65, and the upper base 40.
lower
section
base
of of
whicheach presentingi s
abou t a trapezium,
Through these islands shafts are to be sunk to the
level of the projected tunnel ; and this done, the
work of excavation may be commenced on 28 points
at once. The tunnel once completed, the islands
are to be destroyed by blasting, the Varna Star
being the only one preserved. The tunnel itself is
a vaulted cylinder, 9 metres in diameter. The plane
on which the double rails are laid cuts off a seg-
ment two metres in height, thus leaving a free space
of 7 metres above, affording a sufficient volume of
air. A sewer runs all along below the plane. The
probable expense of this gigantic work is stated to
be as follows :
The construction of the islands fr.24,000,000
Piercing of the tunnel
Masonry
Accessory galleries
10,0)0,000
Branches of Railways
19,000,030
Stations
lolling stock
. Administration
Total fr. 170,000,000
The time requisite for completing this stupendous
undertaking is stated at six years. In the book
which the projector has published on the subject,
he enters largely into all the difficulties to be fore-
seen in the execution, especially the question of
the infiltration of water ; and expresses his convic-
tion,t dst
founded on
whichonthenianttuerreruopftetdhetbseeicl,ontshtartuentoionne
of
of the Thames Tunnel are to be apprehended in
the present case.