Daily Kennebec journal. [microfilm reel] (Augusta, Me.) 1870-1975, 1913-12-05

| on both sides are various layers of
chalk. The top layer is water-bear-
ing white chalk. Below this Is a lay
er of gray chalk, averaging 225 feet in
thickness, and practically dry and i'm
| pervious to water, and through this 1t
| is proposed to drive the tunnel. This
chalk is easily worked, as was dem
onstrated in 1882, when trial headings
were driven successfully by means of
a rotary cutting machine operated by
compressed air. 1t was estimated at
! that time that circular heading
| feet in diameter could be driven out
! from each shore to a meeting under
| the center of the channel in two years.
In three years the tunnel could have
been completed, since the stopping"
! or enlarging the tunnel to its full Sec
tion, and the excavation of ventilation
and drainage galleries would have fol-
lowed closely behind the driving of
| the headings in accordance with the
usual tunnel practice.
| The natural place for the tunnel is
at the Strait of Dover, where the dis
| lance from coast to coast is only about
% miles and where the average depth
Of water is about 100 feet. This mar
row strip OF water has always been
one of the important international
/ highways of the world, and the traffic
! lines on both coasts converge to 1t.
! But Il is also a most unsatisfactory
| highway on account of the swift cur
/ rents and rough seas to which 1t Is
/ subject. The economic Importance of
/ the strait as a link between England
! and the Continent will never be al
! tered, and it is therefore inevitable
that a tunnel providing adequate rail-
way transportation viii finally be
| built.
! The tunnel, as proposed, will run
from the Shakespeare cliffs near Do
! yer. England, to Sangatte, on the
| French Coast, near Calais, and its to-
/ tai length will be little more than
| % miles. On each side it will enter
| tho cliffs at short distance from the
shore and drop down on a grade of l
! IN SO for about two miles into the i'm
| pervious gray chalk under the strait.
| From each of these low points the
| grade will rise at the rate of l in
! 1000 to summit under the middle Of
! the strait, the thickness of the gray
/ chalk being great enough to permit
| this arrangement. The plan for plac-
| ing a summit at the middle of the tun-
! mel is solely for the purpose of drain
| age. Such a plan does away with the
necessity for separate drainage tun-
rels which would require a rather
elaborate arrangement of shafts con-
Meeting the main tunnel with the
| drainage tunnels. At each of the low
| POINTS near shore collecting basin
will be placed. The water will flow
! into these by gravity and will be re-
moved by means of force pumps.
The plan now under consideration
provides for two parallel tunnels con-
nected by passageways at frequent in
tervals. 1t is difficult to see the nee
! ossity for this arrangement, since the
| builders would then have to drive two
separate headings and the work of
construction would be practically two
separate tunnel jobs. The approved
modern practice in building tunnels in
rock is to drive one heading, excavate
| from this a tunnel wide enough for
the two tracks and then support the
center with concrete wall, as is being
cone in the Mount Royal tunnel at
Montreal. There is no apparent rea-
son why this process would not be
adapted as well to a tunnel in such a
| stratum of chalk as exists under the
strait. The heading could easily be
cxcavated by means of a rotary cut
| ting machine, driven either by cleo
| tricity or compressed air. If driven
by compressed air. the exhaust from
the machine, by introducing con-
| slant supply of fresh air into the
| or 70 ri SOlN-
ing the problem of ventilation during
! the construction period. With such
continent as is now to be had per-
manent ventilation after it was placed
| in operation would not be a difficult
matter. The pistonlike action OF the
trains in passing through the tunnel
would practically settle this question,
| although some auxiliary system Oh
supplying fresh air through ducts TO
noints near the middle would DOUBT
| less be necessary. In 1882, it was pro-
posed to use compressed-air engines
for hauling the trains, but at the
present time it is not likely that any
nower other than electricity would pc
| thought OF.
A careful estimate places the cost OF
the tunnel at $S0,000,00 Given the
money and the permission to build it.,
the actual work of construction would
not be as difficult as many engineering
Jobs that attract less attention. The
| critical feature is that of defense in
time of war. Several methods have
been proposed for blocking the en-
trance to prevent invasion. Such a
tunnel as that outlined above could
be flooded so that it would be impossl-
BILE for an enemy to pass the low point
in the grade AS an additional safe
guard it has been proposed to build a
! device similar to a cross valve, placed
within the tunnel at a suitable dis
| lance from the entrance. This device
would consist of a massive block OF
| concrete operated by a turntable me-
chanism and pierced with openings
corresponding to the openings in the
tunnel. Under ordinary conditions
| this would be set to permit the pass
age of trains, but in time of war 1t
could easily be turned with the open
ines at right angle to the tunnel and