The daily Cairo bulletin. (Cairo, Ill.) 1878-1???, 1881-05-31
Tunneling the English Channel.

Cleveland Herald
Progress has been reported in the
work of constructing q railway tunnel
under the Straits of Dover between Eng
land and France. The operations have
so far been conducted with satisfactory
results, and the managers Of the enter
prise are hopeful OF final success, al
though 1t is altogether too early to
speak with any confidence, as the point
where the real difficulties Of the under
taking may be looked for have not yet
been reached.
The feasibility of tunneling under the
bed of the English Channel, between
Dover and Calais was asserted many
years ago by engineers of experience.
The ground for their belief was tho
identity of the geological formation Of
the opposing shores, and other eviden-
ces OF a continuity Of the geological for
nation common TO both sides. Sound
ings made at very short intervals along
the line between tho opposing head
lands confirmed this theory. The chalk
bluffs on both sides of the channel rest
upon blue clay, and the lower part of
the chalk formation, to great thick
ness, is OF clayey character sufficient
ly impelvious TO water to permit boring.
The sounding showed this formation to
extend across from shore to shore de-
scending gradually to q depth of $50
feet below high water in mid-channel,
and rising at the same gradient to the
other side.
In lSI2 company was organized to
make atunnel that would permit rail
way transit under the twenty-one miles
OF water between the two countries Mt
their nearest approach to each other.
Preliminary surveys were made and
the results presented to the Govern
ments of France and England with APP
peal for countenance and acid. A joint
commission was appointed to investi-
gate on behalf of the two Governments.
Concessions were subsequently obtained
from both countries, with assurance
that If private enterprise should demon
strate the praclicability of the under,
taking, material aid would DO furnished.
With this encouragement work was be-
gun. Trial shafts were sunk on both
shores to determine the character and
thickness Of the chalk formation intcn-
ded to be pierced 1t was determined
to follow the line of the lower or gray
chalk of depth of 200 feet below tho
bed of the channel at the lowest point
of the line.
These preliminaries occupied several
years, When all preparations had been
made, the work upon the tunnel was
commenced. The plan proposed is to
follow by descending tunnel the nat
ural eastward dip of the gray chalk to-
ward Dover, until the depth of 200 feet
below the sea-bed is reached, and then
to push straight across the channel
with horizontal passage-way until tho
opposite shore is reached. The tunnel
will then sweep around and ascend to
the surface by an incline, following tho
dip of the chalk formation as on tho
English side. The gray chalk is in this
method entered and followed in its nat
ural position throughout, from daylight
on one side of the channel to daylight
on the other. 1t is proposed to carry a
circular bore, seven feet in diameter,
from side to side, when this has been
accomplished, the two Governments
agree to subsidize the work, that il NAV
be enlarged to the dimensions required
for practical operation.
The cutting is done by boring ma
chine advancing half an inch a min
ute. The horizontal bore has reached
but short distance beyond low-water
tide level on the English side, and it is
notyet known whether difficulties NAV
be expected from jets of water forcing
their way through cracks and assures.
The problem which the first boring is
intended to solve is the possible-and
observation-disclosures Of break or fault in
the chalk about midway of the channel,
causing a deep assure. Should this ex-
list, all hope of tunnel communication
would be at an end. With the boring
continued increasingly at the present
maximum rate of sixty feet day, it
will be considerable time before the
ten and a half miles of midchannel arc
bored through and the existence or non.
existence of the dreaded central assure
demonstrated.