TUNNELS, ANCIENT AND MODERN.
It is hardly necessary to say that the great rival to the Mont Cenis
or Summit Railway is the railway that is to be laid through the
tunnel, which, in the official documents of both France and Italy
is denominated “The Great Tunnel of the Alps.” But before we enter
upon the description of this tunnel, an account of subterraneous
construction from the earliest period we have been able to trace
tunnels, may not be uninteresting.
Tunnelling through hills and mountains is not exactly “as old as the
hills,” but the practice, nevertheless, is of great antiquity.[123]
Yet, the oldest tunnel of which we have record was neither through
hill nor mountain, but was carried beneath the course of the River
Euphrates. This happened no less than 4,812 years ago, for it was at
that time that Semiramis was appointed by her dying husband, Ninus,
King of Assyria, Regent and guardian to their only child, the infant
Ninias. The royal widow, according to Diodorus the Sicilian, the most
trustworthy historian of antiquity, who has written of the peoples
that existed earliest after the world’s creation, commenced her reign
2,944 years before the birth of Christ, and immediately afterwards, the
building of Babylon was begun, by two millions of men, who had been
collected, by regal command, from all parts of the empire. The mighty
city was erected on the two sides of the Euphrates, on each bank of
which was raised a palace of colossal proportions. These the Queen
Regent connected together by “a passage under the river,[124] in the
nature of a vault, from one palace to another, whose arches were built
of firm and strong brick, and plastered all over on both sides with
bitumen, four cubits thick. The walls of this vault were twenty bricks
in thickness, and twelve feet high, and the breadth was fifteen feet.
This piece of work was finished in 220 days, and the river flowing
over the vault. Semiramis could thus go from one palace to the other
without passing over the river. She made likewise two brazen gates at
either end of the vault, which continued to the time of the Persian
empire.” The passage was made, not by the process of tunnelling as we
now understand it, but by first making enormous works for diverting
the course of the Euphrates; then restoring it to its ancient channel
as soon as the vaulted passage had been completed. The investigations
of Mr. A. H. Layard, M.P., from 1846 to 1851, show that the process of
making underground connections was fully understood from the earliest
period of Assyrian history.
The ancient Egyptians were undoubtedly masters of the art of
tunnelling. In a very interesting letter received from our much valued
friend George Groves, Esq., the secretary of the Palestine Exploration
Fund, enclosing the recent reports of Lieutenant Warren, R.E., the
writer says, “you will see by Warren’s papers that there is no lack of
tunnels at Jerusalem; in fact, the whole of the rock upon which the
city is built, appears to be honeycombed with them, but of what exact
age they are, it is impossible for us as yet to tell.”
The further reports of Lieutenant Warren cannot fail to be looked for
and read with an all-absorbing interest by every lover of biblical
literature and history. Already his researches and discoveries show
that he is a man with whom his countrymen may well be satisfied. True
type of the Englishman, he is earnest, indefatigable, and enduring;
incapable of fatigue, he never knows what it is to be beaten. His
ordinary work extends not only throughout the day with a temperature
varying from 100 to 107, but also far on towards midnight. But at that
period of the 24 hours, the Lieutenant says, “the temperature is much
cooler.” That is, the thermometer falls to about 80! Recently when
having “an attack of incipient fever and not being able to shake it
quite off,” he with his faithful assistant and humble companion in
all his labours and anxieties, Sergeant Birtles, “who was also very
unwell,” went for a three days’ ride through Faghur, &c. “We returned
on Saturday quite recovered!” Twelve or thirteen hours a day in the
saddle for three successive days, is rather a rough remedy for the cure
of fever.
We limit ourselves to two extracts from the reports; the first relates
to a discovery made as recently as the 1st of September last, which may
be truly described as one of very great importance.
“I have made what I consider to be a very important discovery,
viz., an ancient aqueduct, south-east of the south-east corner of
the Cœnaculum, and fifty feet above the present aqueduct—I have no
doubt the original aqueduct from Solomon’s Pools to the Haram Area.
We dug out the earth from a cut stone shaft two feet square, and at
sixteen feet was a channel running from the west to the north-east,
precisely similar in construction to the passages under the Triple
Gate. It varies very much in size. Sometimes we could crawl on hands
and knees; then we had to creep sideways; again we lay on our backs
and wriggled along; but still it was always large enough for a man
of ordinary dimensions. In parts built of masonry, in parts cut out
of solid rock, it is generally of a semi-cylindrical shape; but in
many parts it has the peculiar shoulders which I have only seen
under the Triple Gateway, but which I told you in my last letter had
been noticed by Mr. Eaton in the channel leading towards Tekoah. To
north-east we traced the channel for 250 feet, until we were stopped
by a shaft which was filled with earth; to the west we traced it for
200 feet, till it was stopped in the same manner. In part of this
passage we could stand upright, it being ten or twelve feet high, with
the remains of two sets of stones for covering, as shown in M. Piazzi
Smyth’s work on the Great Pyramid; the stones at the sides being of
great size—12 feet by 6. This channel cannot be so late as the Romans.
It is evidently of most ancient construction. It is built in little
spaces, as if the work had been commenced at two or three points,
and had not been directed properly. The plaster is still in good
preservation. I shall have the passage cleared out, if possible, as
far as the city walls. I presume it goes into the Haram, at a slightly
higher level than the present aqueduct. If so, by following it we may
arrive at some very interesting conclusions as to the original method
of supplying the Temple with water.
“This channel must have been of great consequence in olden times, both
from the distance it is driven under ground, and from the well-cut
shafts which lead to it. I think the question is to be hazarded
whether the supply of Jerusalem was not obtained by this aqueduct,
which is quite concealed from an enemy.”
At the date of the last report the tunnel had been traced about 300
feet to the north-east, where it appears to fall into the present
aqueduct.
Our second and concluding extract will show the difficulties and
dangers attending upon the labours of Lieutenant Warren and his party,
as well as the necessity which exists for funds coming in liberally to
meet the very heavy expenses of these marvellous explorations.
“PROGRESS OF WORKS TO 11TH OCTOBER, 1867.—_Shaft near S.W. angle South
Wall of Haram Area._—Depth excavated, to Thursday, the 10th October,
76 feet.
“On Friday, having arrived at a depth of 79 feet, the men were
breaking up a stone at the bottom of the shaft. Suddenly the ground
gave way, down went the stone and the hammer, the men barely saving
themselves. They at once rushed up and told the sergeant they had
found the bottomless pit. I went down to the spot and examined it,
and, in order that you may have an idea of the extent of our work, I
will give you a description of our descent.
“The shaft mouth is on the south side of the Haram Wall, near the
south-west angle, among the prickly pears; beside it, to the east,
lying against the Haram Wall, is a large mass of rubbish that has been
brought up; while over the mouth itself is a triangular gin with iron
wheel attached, with guy for running up the excavated soil. Looking
down the shaft, one sees that it is lined for the first 20 feet with
frames 4 feet 6 inches in the clear; farther down, the Haram Wall
and soil cut through is seen, and a man standing at what appears to
be the bottom. An order is given to this man, who repeats it, and
then, faintly, is heard a sepulchral voice answering as it were from
another world. Reaching down to the man who is visible is a 34 feet
rope ladder, and, on descending by it, one finds he is standing on
a ledge which the ladder does not touch by 4 feet. This ledge is
the top of a wall running north and south and abutting on the Haram
Wall; its east face just cuts the centre of the shaft, which has to
be canted off about 2 feet towards the east, just where some large,
loose stones jut out in the most disagreeable manner. Here five more
frames have been fixed to keep these stones steady. On peering down
from this ledge, one sees the Haram Wall with its projecting courses
until they are lost in the darkness below, observing, also, at the
same time, that two sides of the shaft are cut through the soil and
are self-supporting. Now to descend this second drop the ladder is
again required; accordingly, having told the man at bottom to get
under cover, it is lowered to the ledge, from whence it is found that
it does not reach to the bottom by several feet. It is, therefore,
lowered the required distance, and one has to reach it by climbing
down hand over hand for about 12 feet. On passing along, one notes the
marvellous joints of the Haram Wall stones, and also, probably, gets a
few blows on skull and knuckles from falling pebbles. Just on reaching
the bottom, one recollects there is still a pit of unknown depth to
be explored, and cautiously straddles across it. Then can be seen
that one course in the Haram Wall, near the bottom, is quite smooth
all over, the stone being finely dressed, all other courses being
only well dressed round the drafts; one also sees two stout boards
lying against the Haram Wall, under which the men retire whenever an
accidental shower of stones renders their position dangerous. One is
now at a depth of 79 feet from the surface, and from here we commence
the exploring of the “bottomless pit.” After dropping a rope down, we
found that it was only six feet deep, though it looked black enough
for anything. Climbing down, we found ourselves in a passage running
south from the Haram Area, 4 feet high by 2 feet wide, and we explored
this passage. It is of rough rubble masonry, with flat stones at
top similar to the aqueduct from Triple Gate, but not so carefully
constructed. The floor and sides are very muddy, as if water gathers
there during the rainy season.
“It at once struck me that it was one of the overflow aqueducts
from the Temple of Solomon, and that there might be a water conduit
underneath. We scrambled along for a long way on our feet, our skulls
and spines coming in unhappy contact with the passage roof. After
about 200 feet we found that the mud reached higher up, and we had to
crawl by means of elbows and toes. Gradually the passage got more and
more filled up, and our bodies could barely squeeze through, and there
did not appear sufficient air to support us for any length of time; so
that, having advanced 400 feet, we commenced a difficult retrograde
movement, having to get back half way before we could turn our heads
round. On arriving at the mouth of the passage underneath the shaft,
we spent some time in examining the sides, but there is no appearance
of its having come under the Haram Wall. It seems to start suddenly,
and I can only suppose it to have been the examining passage over an
aqueduct coming from the Temple, and I am having the floor taken up to
settle the question. This passage is on a level with the foundations
of the Haram Wall, which are rough-hewn stones—perhaps rock; I cannot
tell yet. The bottom is the enormous distance of 85 feet below the
surface of the ground, and, as far as I can see as yet, the wall at
the south-west angle must be buried for 95 feet under ground, so that
it must at one time have risen to the height of 180 feet above the
Tyropœon Gully. I consider it very unsafe sinking these shafts without
sheathing them; but I have been obliged to do so for want of wood.
In this shaft in particular there is about 60 feet unsheathed, and a
loose stone from any part might stave a man’s head in before he is
aware of it. I think it running needlessly into danger; and I hope
that, with what you are sending from England, and what I am getting
from Malta and Alexandria, I shall soon have enough to go on with in
a business-like manner. The amount of wood wanted is very great. This
shaft, when sheeted, would require 100 boards 18 feet long, and 9
inches by 1 inch. We are also very much in want of English dockyard
rope and rope ladders; all the work here consisting of driving shafts
of great depths, it is necessary to have many ladders. We have
only two, and are often in great difficulties about it. It is all
very well climbing hand over hand thirty-five feet up a rope, when
hanging in the air; but when it is in an unsheathed shaft, with the
dangling bringing down the loose stones on the head, it is unsafe. The
anxiety of mind caused lately, by having to keep the workmen going
without adequate means for their protection, is more than I can put
up willingly with any longer. _We must have plenty of money for the
excavations, or stop them altogether._”
The oldest tunnel, of which we can find any record or mention in
Europe, is that constructed in connection with a great aqueduct built
about 540 years B.C. in Boetia, to draw off the waters of the lake
Copais, now called lake Topolias, to the sea then called the gulf of
Opuntius, and now the Channel of Talanti. The tunnel, nearly a mile in
length, became impeded and choked up, and, about 220 years afterwards,
was ordered to be restored by Alexander the Great, who had previously
“fleshed his maiden sword” in its neighbourhood at one of the few great
and decisive battles of the world—that of Chœroncia. It was fought and
won by Philip of Macedon, 338 years before the birth of Christ.
As to how the rock was penetrated in the absence of the modern
appliance of gunpowder, we are now as ignorant as we are of the
mechanical means by which the great pyramids of Egypt and other
gigantic works there, were constructed; and we are in the like state
as regards a tunnel in the Island of Samos, which we learn on the
authority of Strabo was 4,200 Greek feet long—equal to 4,230 modern
English feet—that is more than three-quarters of a mile. The height of
the mountain through which it was driven was 900 Greek (907 English
feet), and its purpose was to supply with water the principal city of
the island, the inhabitants of which, 2,600 years ago, were among the
most active and enterprising merchants and shipowners of the world.
Ancient Samos, now called by the Turks _Susam Adasi_, is the nearest
to the coast of Turkey in Asia of the numerous islands which dot the
Eastern Archipelago.
Albano is the first halting station of the day express train from
Rome to Naples; close to it is the Alba lake seven miles round, at an
elevation of 700 feet above the level of the sea. 2,000 years ago the
Romans constructed a duct to carry off its superfluous water into the
Tiber; part of the duct is through a tunnel, which, in consequence of
modern repairs, is still in a state of perfect preservation. It is a
little more than a mile long, and its dimensions are 6 feet high and 4
feet wide; it was completed in a year.
But the grandest tunnel of ancient Italy is the underground canal
constructed by the orders of the Emperor Claudius to draw off the
waters of the lake then called Fucinus, now Celano, into the River
Siris. This stupendous work, three miles long, and nowhere less than
twenty feet high, required the labour of 30,000 men for eleven years to
accomplish. It has several shafts as in modern tunnels; it is now in a
sound state, having been solidly repaired only a few years ago.
In the second volume of _La Vie de Cæsar_, by the Emperor Napoleon
III., pages 412, _et seq._, (English edition) will be found the account
of the siege of Uxellodum (_Puy d’Issolu_, near Vayrac), the capture
of which by Julius Cæsar, U.C., 703, put him in complete possession
of Gaul. The town, surrounded on all sides by steep rocks, was, even
without being defended, difficult of access to armed men. It was
also well provisioned, but, as its water supply was derived from an
abundant spring which arose at the foot of the wall of the town, 300
feet from the channel of the River Tourmente, “Cæsar resolved,” says
his Imperial historian, “to drain this spring, and for this purpose
he did not hesitate to attempt a laborious undertaking. Opposite to
the point where the spring rose, he ordered covered galleries to be
pushed forward against the mountain, and, under protection of them, a
terrace to be raised. Although these works were attended with great
danger and fatigue, they were vigorously persevered in. At the same
time, a subterranean excavation on a lower plane than the fountain,
and running from the galleries, was made. This work, carried on, free
from all danger, was executed without being perceived by the Gauls;
the terrace attained a height of sixty feet, and was surmounted by a
tower of ten stories, which, without equalling the elevation of the
wall of the town, a result it was impossible to attain, still commanded
the fountain. Its approaches, battered by engines from the top of
the tower, became inaccessible; in consequence of this, many men and
animals in the place died of thirst. Nevertheless, the Gauls did not
yield. At last, the subterranean gallery having reached the veins of
the spring, they were taken and turned aside. The besieged seeing
the fountain all at once dried up, believed, in their despair, that
it was an intervention of the gods: they submitted to necessity, and
surrendered.” Researches made for the purposes of the _Vie de Cæsar_,
by M. J. B. Cessac, assisted subsequently by the Permanent Commission
of the Department du Lot, have brought this tunnel fully into view. It
was carried through the marl; and the proof that the Roman soldiers
had not boring tools suited for penetrating rock is afforded by the
fact that, when they came upon it, they deviated in the expectation
that they would come upon the tufas which, formed by the waters, would
necessarily lead towards the spring. The Roman soldiers were right in
their expectations.
The galleries and tunnel, as well as the siege-works, are illustrated
by two plates, No. 31 and 32 of the Appendix. The tunnel was about 550
yards long. During M. Cessac’s investigation the timber which supported
part of it still existed.
The earliest mention that we have of tunnelling in connection with
the Alps dates back more than 400 years. Anne,[125] Duchess of Savoy,
conceived the grand project of piercing the Col di Tenda, then, and
for nearly two centuries and a-half afterwards, the best and easiest
pass available between France and north-western Italy, with a tunnel
at about one-third of its height from the summit. It appears, beyond
doubt, that the works were begun, but at the death of Anne they were
abandoned; after a lapse of three centuries they were resumed in 1782
by order of Victor Amadeus III., King of Savoy. The excavation of the
mountain was continued, although not vigorously, until 1794, when it
was abandoned, in consequence of the invasion of Savoy by the French.
The total length of the tunnel would have been about 3,000 yards, and
by means of it a precipitous sugar-loaf ascent of 1,300 feet to the top
of the pass would have been avoided. At the present time the idea of
the tunnel is revived, it being proposed to construct to it a railway
on the Fell system,[126] from Cuneo at the foot of the pass, which
place is now connected with Turin and the whole system of Italian
railways by a line fifty-four miles long. The Cuneo district is one
of the most productive of the fertile plains that fringe the southern
slopes of the Alps, and extend for a width of from fifty to sixty miles
beyond them.
We did not begin either to make canals or to tunnel in Great Britain
until a little more than a century ago. Now we have 2,200 miles of
inland navigation, of which 213 are in Scotland and 297 in Ireland.
Brindley, the engineer of the Duke of Bridgewater, commenced the
Harecastle Tunnel on the Trent and Mersey Canal in 1765, but it took
him eleven years to finish it. It was not until 1776 that the first
boat was able to go through it. The tunnel is 2,880 yards long, 12
feet wide and 9 feet high. Although Brindley was much troubled with
quicksands, the work was completed for the marvellously small sum of
£3. 10s. 8d. a yard forward. Some years afterwards, in consequence of
the immense increase of the business of the canal, Telford constructed
another Harecastle Canal alongside the first, the dimensions of which
are—length, 2,936 yards; width, 14 feet; height, 16 feet.
The longest canal tunnel—indeed, the longest tunnel, whether railway or
canal—in England is the Marsden, on the Huddersfield Canal, 5,450 yards
(3 miles and 170 yards), thus exceeding the longest railway tunnel
by 154 yards. The lengths in yards of some of the principal canal
tunnels of England are as follows:—Sapperton (Thames and Severn),
4,180; Lapal (Dudley), 3,776; Blisworth (Grand Junction), 3,080; Tipton
Green, 2,926; Oxenhall, 2,192; Foulbridge (Leeds and Liverpool), 1,640;
Asperton (Hereford and Gloucester), 1,320; Fenny Compton (Oxford),
1,188. From this list we exclude the Old Thames and Medway Canal
Tunnel, near Rochester, because the South-Eastern Railway Company, when
it purchased the canal, converted the tunnel into one suitable for a
railway; its length is 3,740 yards.
The most recently constructed canal tunnel in England is the Netherton
Tunnel, on a branch of the Birmingham Canal, having only been completed
in 1858. It is 3,036 yards long, 27 feet wide, and 24 feet 4 inches
high in the clear. Seventeen shafts altogether were sunk during its
construction, of which ten were closed on being used for traffic. The
greatest depth of any of the shafts is 344 feet 6 inches, the least
65 feet 9 inches. The time occupied for completing this tunnel was
only two years. For full and minute description of this tunnel see
proceedings of the “Institution of Civil Engineers,” Vol. XIX.
The village of Highgate, situated on one of the two northern hills in
the immediate vicinity of London, was to have had a tunnel 301 feet
long, 24 feet wide, and 13 feet high, for the purpose of avoiding the
steep and dangerous hill on the great road which led, and still leads
from London, towards the North. An Act of Incorporation was obtained,
and the undertaking was prosecuted for a time with great energy; but
unfortunately, after 130 yards of the work had been accomplished, the
whole fell in on the 13th of April, 1812. The accident created an
intense sensation, and it was the subject of a drama: “The Highgate
Tunnel, or the Secret Arch,” which for a time was a source of
attraction at one of the minor theatres at the East end of London. The
disaster put an end to the desire for a tunnel, and the present road
was constructed through a deep cutting, by means of which much of the
steepness of the hill was done away with. Hornsey Lane crosses this
cutting, on a noble bridge, which is called the Highgate Arch.
The late Mr. Robert Stephenson, M.P., in his address to the Institution
of Civil Engineers, on his election as President in January 1856,
stated, that “tunnels for railways had traversed hills and penetrated
mountains to the extent of nearly 70 miles,” the miles of railways
opened in the United Kingdom at that time being 8,054.
Mr. J. M. Fraser, in a paper which he read at the Institution of Civil
Engineers, on the 24th of March, 1863, considered, that “it would not
be inaccurate to assume 80 miles as representing the length of tunnels
now daily traversed by railway trains in the United Kingdom.” At that
period there were 11,547 miles of railway in operation. As there were
13,882 miles opened for traffic on the 31st of December, 1866 (of which
about one-third is single line), we may consider that w e have about
90 miles of line “in tunnel” at the present date, and in these are
included the Metropolitan (Underground) Railway and the tunnels[127]
on the New Midland Line between Bedford and London, opened for goods
traffic in August 1867. We knew as a fact that, during the early
construction of railways in England, our engineers resorted to tunnels
to avoid gradients and curves (especially the former) that would almost
be considered favourable at the present day. As experience increased
and the power of the locomotive was developed, so did the amount of
tunnel work diminish. Hence it is that if the three estimates just
stated be correct, the proportion of tunnel to railway on the 1st of
January, 1856, was one mile to every 115; on 1st of January, 1863,
one to every 144 miles; on 1st of January, 1867, one to every 154.
Had Ireland been excluded from the reckoning,—as she might well be,
seeing that there are only three there of the aggregate length of 2,980
yards (exactly 100 yards less than a mile and three-quarters) on the
1,948 miles of railway that are now open for traffic in that part of
the United Kingdom,—the proportion of tunnel to railway in England,
Scotland, and Wales would have been one mile of the former for every
132½ of the latter. The number of tunnels in Ireland is, however, it
is alleged, about to be added to, as, since a very serious accident at
“Bray Head,” on the Dublin, Wicklow and Wexford Railway, a feeling of
uneasiness prevails in the public mind as regards the safety of the
line at this point. It is, therefore, contemplated to run four tunnels
through the mountain at its side nearest to the sea, at an estimated
cost of about £23,000. Bray Head, it may be mentioned, forms the
southern boundary of the Bay of Dublin, the Hill of Howth being its
boundary to the north.
The longest railway tunnel in England[128] is the Woodhead or Summit
Tunnel of the Manchester, Sheffield and Lincolnshire Railway. Its
length is 5,296 yards, or 3 miles and 16 yards, with a gradient of
1 in 200, or 26⅖ feet to the mile, the rise being in the direction
from Dunford to Woodhead. The ordinary passenger trains require ten
minutes from Dunford to Woodhead, but trains travelling from Woodhead
to Dunford take a minute less. Therefore, with the gradient favourable,
the speed is only at the rate of 20 miles an hour; against the
gradient, 18. It is a single line tunnel.
The Stanedge Tunnel on the Huddersfield Branch of the London and
North-Western Railway is exactly 3 miles long, and it is also a single
line tunnel; the gradient is nearly a level. The time for passenger
trains through it is six minutes, or at the rate of 30 miles an hour;
the time for goods trains is nine minutes, or at the rate of 20 miles
an hour. The deepest portion of the tunnel is 600 feet below the upper
surface of the mountain.
On the 3rd September, 1867, we came through the Shepherd’s Well Tunnel
of the London, Chatham and Dover Railway, 2,376 yards long, against
the gradient, which is 1 in 100, or 53 feet in the mile for two-thirds
of its length, and the remainder nearly level, in two minutes fifteen
seconds; on the same day we came through the tunnel in the opposite
direction, when the time occupied was one minute forty-two seconds:
on the other hand, Mr. Allport, the General Manager of the Midland
Railway, to whom we gladly acknowledge ourselves indebted for much
valuable information most obligingly afforded, says that the passenger
trains are timed to run _in each direction_ through the Dove’s Hole
Tunnel 2,420 feet long at the same rate of speed, and actually do run
at that speed—nearly 46 miles an hour,—yet the gradient is 1 in 90, or
58⅔ feet per mile. The same for goods trains, their speed is 23 miles
an hour in each direction, and Mr. Allport assures us they maintain it
in both directions.
The following are the lengths of some of the principal railway tunnels
in Great Britain and of the two longest in Ireland:—
Name. Company. Yards.
Medway South-Eastern 3,740
Sevenoaks ” 3,600
Box Great Western 3,227
Littleborough Lancashire and Yorkshire 2,869
Sapperton Great Western 2,800
Pohhill South Eastern 2,750
Kilsby London and North-Western 2,423
Dove’s Hole Midland 2,420
Shepherd’s Well Chatham and Dover 2,376
Wapping (L’pool) London and North-Western 2,250
Lime Street ” ” 2,230
Clayton London and Brighton 2,200
Sydenham Chatham and Dover 2,190
Abbot’s Cliff South-Eastern 2,000
Watford London and North-Western 1,793
Merstham South-Eastern 1,780
Clay Cross Midland 1,780
Sapperton(A) ” 1,760
Corah Wood Newry and Armagh 1,510
White Ball Bristol and Exeter 1,470
Belsize Midland 1,460
Grenfield Midland 1,400
North-Eastern 1,364
Thackley Midland 1,360
Honiton London and South-Western 1,350
Bletchingly South-Eastern 1,324
Lydgate Lancashire and Yorkshire 1,322
Wichwar Midland 1,320
Shanklin Isle of Wight 1,320
Shakspeare South-Eastern 1,320
Almonsbury Bristol and South Wales 1,320
Kilbarry Great Southern and Western 1,290
Primrose Hill London and North-Western 1,250
Glasgow Edinburgh and Glasgow 1,250
Potter’s Bar Great Northern 1,210
Balcombe London and Brighton 1,122
Brislington (No. 1) Great Western 2,200
Brislington (No. 2) ” 1,100
Brislington (No. 3) ” 330
North Welwyn Great Northern 1,046
Penscliff ” 968
Guildford London and South-Western 965
Saltwood South-Eastern 954
Bangor Chester and Holyhead 910
Chislehurst South Eastern 900
Elstree Midland 900
Gillingham Chatham and Dover 895
Stoke Great Northern 880
Milford Midland 836
Calandar Edinburgh and Glasgow 830
Whitstable South-Eastern 822
Haddon Midland 800
Oakley ” 800
Bishopton Glasgow and South-Western 760
Coates Park Midland 740
Buckhorn Weston Salisbury and Yeovil 739
Belmont Chester and Holyhead 737
Penmaen Bach Chester and Holyhead 721
Tottenham Great Northern 714
Leeds North-Eastern 700
Copenhagen Great Northern 694
Dover Chatham and Dover 682
Manton Midland 660
Ampthill ” 640
Chivet ” 620
Martello South-Eastern 616
Barnet Great Norther 605
Chelsfield South Eastern 600
(A) Followed by an open cutting of 100 yards; then a tunnel of 440
yards. The gradient in these tunnels is 1 in 70. For full details
respecting them, see Paper read by Mr. Charles Nixon at the Institution
of Civil Engineers. _Proceedings_, volume for 1842.
Some of our tunnels have been extremely costly, the Kilsby, for
instance, £125 per yard forward, total £302,000. The face of the
Primrose Hill Tunnel at its London end cost £7,000, thereby adding to
its total cost at the rate of £5. 15s. a yard. Up to 1857, the average
cost of all tunnels was £102 per yard, or for 70 miles £12,320,000.
Tunnels have certainly been constructed more cheaply since then.[129]
Mr. J. G. Fraser assumes them to have cost at the average rate of
£45 per lineal yard, but this must be considerably below the mark,
notwithstanding that many of the more recently constructed tunnels have
only been for “single line.” The dimensions of these tunnels on the 4
feet 8½-inch gauge, are usually as follows:—12 feet wide at rail level,
17 feet from rail level to soffit, whilst for a double line of the same
gauge tunnels are usually about 25 feet wide at rail level, and about
22 feet from rail level to soffit. On the exceptional Great Western
gauge, they would be respectively about a fourth higher and a third
wider.
We must only touch the Thames Tunnel at a tangent. Its length is 1,200
feet with two arches each 13 feet 9 inches at the springing of the
arch; 16 feet 4 inches high from the invert. It cost £1,000 a yard, or
for 400 yards £400,000, two and a-half times as much per yard forward
as the most expensive estimate for the Mont Cenis Tunnel, more than
three times as much as its cost per yard forward up to the present
time. In addition, the approaches of the Thames Tunnel (for foot
passengers only) cost £54,714, total £454,714. It is now about to be
utilised as a railway tunnel, having been purchased by the East London
Railway Company for the purpose of bringing together the lines at the
north-eastern and south-eastern ends of London.
As a rule, the tunnel mileage (except in one country only, Spain) is
much less in proportion to total mileage on the various continental
railways than it is in England. This is especially the case in almost
all the more recently constructed lines, but more particularly so in
Germany. Here, the ingenuity of the engineer has been exercised to
avoid tunnels wherever possible, and not to seek them. We might cite
many instances in proof, but limit ourselves to one, which must be
familiar to many—the line along the left bank of the Elbe, between
Dresden and the Austrian frontier at Bodenbach, through the beautiful
Saxon Switzerland. There are, however, tunnels in Germany, the longest
of which is that which has already been mentioned, the summit Tunnel of
the Sœmmering Pass, 1,565 yards, just 195 yards less than an English
mile.
There are long tunnels in France, both canal[130] and railway, and as
regards the first-named class, our readers will hardly be prepared
to learn that there has existed for forty-five years in France, an
underground passage at Cunhardy called a tunnel, which is in length
only 314 yards less than the Great Tunnel of the Alps; yet such is
the fact,—the Norieu underground passage which forms a portion of the
_Canal de St. Quentin_, is 13,128 yards long, or 7½ miles all but 72
yards. Its maximum depth below the surface is 86 yards. It is only 4
feet 11 inches wide and is without towing path. It was opened in 1822
at a cost of only £2. 12s. per yard. Seven years were occupied in its
construction. But the most important canal tunnel in France, in respect
of its width and elevation, is that of Rigueval, which is also on the
_Canal de St. Quentin_. It is 6,237 yards long, 26 feet 2 inches wide,
of which 5 feet 3 inches are for the towing path along which horse
traction is used. The Tunnel of Manvages, 5,320 yards long, is on the
_Canal du Marn au Rhin_. Of the two other long canal tunnels (both on
the _Canal de Bourgogne_), that of Sousey is 3,873 yards long, 7 feet 3
wide. It has not a towing path. That of Pouilly is 3,630 yards long and
20 feet 2 inches wide, including a towing path of the width of 5 feet
3 inches. The cost of the Sousey was £9. 4s. a yard; of Pouilly £80 a
yard.
The longest railway tunnel in France is that of La Nerthe on the Paris,
Lyons and Mediterranean Railway, between Avignon and Marseilles. It is
4,638 metres (5,101 yards). It cost £90. 10s. per metre. Its shafts
vary in depth from 65 to 623 feet.[131] There are twenty-four of these
shafts, which are not over the centre of the tunnel, but about 30 feet
on one side. They communicate with it by lateral galleries 10 feet
wide, and as high as the tunnel itself. The shafts are all circular,
about 10 feet wide, and have all been left open. The gradient from
one end to the centre is 1 in 500—10½ feet in the mile. It then falls
to the other entrance at the rate of 1 in 1,000. The tunnel of Blaisy
on the same line, near Dijon, is 4,100 metres (4,510 yards). It cost
£77 per metre. It had twenty shafts during construction, of which ten
are now closed. Nine of the shafts are from 515 to 643 feet below the
surface. They are not over the tunnel, but about 32 feet on one side,
and connected to it by lateral galleries. The Credo Tunnel on the
Geneva Branch of the same line 3,949 metres (4,344 yards), £65. 12s.
per metre. There are several other long railway tunnels in France. That
of Rilly near Rheims, is 3,500 metres long. There were nine shafts
during construction, of which four were closed when the railway was
opened. Although lined with masonry throughout, the thickness being 20
inches in compact chalk, and 32 inches in that which was seamy, the
cost was only £28. 15s. per yard. Hommarting Tunnel (_Chemin de Fer de
l’Est_), is 2,780 metres long, Pissy Poville, 2,400 metres; Tarare is
a very long one but we are not sure of its exact extent. The Tunnel of
Arschwiller, on the _Chemin de Fer de l’Est_, is 2,678 metres, and is
close to the tunnel of the canal from the Marne to the Rhine, named on
the previous page the Tunnel of Manvages. In fact, where they enter the
mountain they are at the same level, and a double arched entrance—the
intervening pier being only 22 feet thick, and the arches precisely
similar—receives them both. The canal tunnel was completed before that
for the railway, which latter diverges from the line of the former at
the rate of 26 feet in 1,000, so that at the end of the railway tunnel
it is 60 feet from that of the canal. The canal then makes a bend and
presently crosses _over_ the railway tunnel, as it has a descending
gradient of 1 in 200, and at what may be called its diverged entrance,
it is 44 feet below the level of the canal. The railway tunnel took
nearly eight years to construct at a cost of £38. 10s. per metre
forward.
There is also a large number of tunnels from 500 to 1,500 metres long.
The price per metre forward varies nearly as much as in England, its
maximum being £95, that of Batignolles, near Paris, on the _Chemin de
Fer de l’Ouest_, a short one, only 333 metres (366 yards); minimum
£30, that of Terre Noire 1,641 metres, on the Paris, Lyons and
Mediterranean.
The longest railway tunnel in Belgium is that of Braine le Compte,
641 metres (705 yards). It cost £46 a metre. There are altogether
eighteen tunnels along the 15½ miles of picturesque line of railway
between Liege and Verviers; they are all short, none exceeding 400
metres in length; their cost was exactly £50 a metre forward. There is
only one long tunnel in Switzerland, that of Hauenstein near Olten,
on the railway between Basle and Berne, its length is 2,731 yards,
and, notwithstanding the numerous difficulties which attended its
construction, its cost was only £80 per yard. It might be expected
that in an undulating country like Switzerland there would be a great
many tunnels on its railways; such, however, is not the case, the
larger proportion of the railways are constructed in the comparatively
level valleys, and when engineers come upon rough ground, as a rule,
they prefer stiff gradients to very expensive works. This, however is
not always the case; witness the passage of the Jura from Pontarlieu
towards Neufchatel; here there is the combination of expensive works
with a steep ascending and then a steep falling gradient. These might
have been greatly alleviated, if not altogether avoided, by a tunnel of
comparatively short length; the engineer, it is said, wished to erect
for himself, in this work, a monument _perennius ære_. He has succeeded.
The longest tunnel upon a railway in Italy, now open for traffic, is
on the Giovi incline, near Genoa, 3,225 yards, or five yards over two
miles. The longest of the two on the Brachia pass of the Apennines,
between Pistoja and Poretta, is (as already stated) 3,300 yards; the
length of the next longest, on the same pass, is 2,860 yards. A tunnel
longer by a few yards than that on the Giovi incline, is in process of
construction on the branch which is to connect Naples by a direct line
with the Adriatic. The tunnel Maggioni, between Florence and Rome, is
1,170 metres (1,287 yards) long.
The natural undulatory, in many places almost mountainous, character of
Spain, has rendered necessary the construction of numerous tunnels on
Spanish Railways. The following is an abridgment of much interesting
information on this subject, published by the Spanish Government last
summer, and translated into French a few weeks ago.
On the line from Madrid to Saragossa, the length of which is 213 miles,
there are twenty-six tunnels; the most important of them is Horna,
1,010 metres. The total length of these twenty-six tunnels is 4,791
metres, or 3⅝ miles. On the Manzanares to Cordova Line, the length of
which is 243½ kilometres, there are thirteen tunnels, the longest of
which is 1,025 metres; their total length 3,092 metres. The Albaceta
to Carthagena Line, is 154 miles long; the chief tunnel is that of
Almadenes, along the gorge of the same name, its length is 1,056
metres. There are four short tunnels on this line, all in the vicinity
of the gorge; their combined length is only 393 metres, making, with
the tunnel of Almadenes, 1,449 metres.
The Northern of Spain—Madrid to Irun—is 399 miles long. Although it
is not the longest, it is probably the most important railway in
Spain, traversing nearly throughout its entire extent, a difficult,
and, at places, an extremely hilly country, and finally terminating
at the Pyrenees, where it meets the Bayonne and Irun Railway. Thus,
on the section from L’Escurial to Avila, 44 miles long, there are
sixteen tunnels, the total length of which is 4,408 metres, all of
which are associated with numerous extremely difficult works of art
in their immediate vicinity, some of the viaducts varying from 95 to
135 feet in height, with other proportional dimensions. It is in this
section that the Guaddarama Mountains are traversed, and, until the
locomotive crossed the Mont Cenis the summit of this railway was the
highest in Europe, 4,505 feet above sea level. On the section between
Otzaurte and Beasain, 33 miles long, there are twenty-three tunnels,
the total length of which is 10,351 metres. Some of the works of art
on this section are magnificent in their character and construction.
The tunnels on the other sections of the line are not so numerous;
nevertheless, they are altogether fifty-eight in number, with an
aggregate length of 22,160 metres, exactly 14 miles.
Turning from the most difficult Spanish railway in point of
construction, to the easiest for the greater part of its extent, the
Seville, Xeres and Cadiz Line, the length of which is 103 miles, we
find that there are no tunnels upon it, although on the section between
Xeres and Cadiz there are several extremely difficult works of art.
The Alar del Rey to Santander Railway is 87 miles long. It has
twenty-one short tunnels upon it, the total length of which is 4,808
metres.
The length of the Palencia and Astorya Line is 110 miles. It runs
from Palencia to Gigon, on the Bay of Biscay. This railway is only in
course of construction. There are several tunnels upon it, of which the
particulars have not yet been published.
The Saragossa and Barcelona Line is 230 miles in length. In the section
between Cervara and Tarrassa, 59 miles long, there are sixteen tunnels.
As their aggregate length is only 3,591 metres, it will be observed
that they are all very short ones. The other portions of the line are
of comparatively easy construction.
The Ciudad Real to Badajoz Railway, 213 miles long, is a line
presenting scarcely any difficulties of construction, and it has no
tunnel upon it from one end to the other.
The principal difficulty connected with the Tudela and Bilbao Line is
that at its terminus at Bilbao, it is barely above the level of the
sea; but it has to ascend 2,060 feet in 29½ miles. There are no heavier
works in all Spain than those upon this section. For more than half
a mile the principal branch of the Ebro has been deviated, and the
railway has been constructed upon the old bed of the river.
On the Barcelona to Santa Coloma Railway there are seven tunnels, very
short in length; the longest is 443 metres long.
The Tarragona to Barcelona Line is 64 miles long; though passing
through a level country for the greater part of its extent, it has one
section—that between Villa-franca and Marterello, in which the rise
is 540 feet in 15 miles. There are five tunnels upon this length, all
short ones; but they were very difficult as regards construction, and
they are very troublesome in maintenance.
The Lerida Reus and Tarragona Line is 63 miles. It has only one tunnel
upon it, that of Terres, 700 metres long.
The Cordova to Malaga Railway, 121 miles, is extremely easy in point of
construction, except for 6¼ miles at the passage of the Guitanas, where
there are no less than twelve tunnels and six great bridges. In one of
the tunnels a singular circumstance was discovered during construction.
The miners suddenly came upon a _crevasse_ or split in the mountain
which extended from its lofty and precipitous summit to a great depth
beneath the part bored through. The space is traversed by a bridge, the
only one in the records of tunnels that we remember to have met with.
There is one very long canal tunnel in Spain—the Canal of Urgel—between
the Ebro and one of its affluents, the Segro. This canal is 90 miles
long and the tunnel is of the length of 5,230 metres.
The grandest canal in Spain for water supply is the “Canal of Isabel
II.” It furnishes the supply for Madrid. It is built after the system
of the ancient Romans—that is, aqueducts constructed in masonry arched
over. Its total length is 45 miles. It has besides, thirty-one tunnels,
partly cut straight through rocks which the canal traverses, and partly
side-cut tunnels (one is five-eighths of a mile long) for obtaining
water. At the present time, when the question of supplying London and
other important cities with water is much agitated, it may be well to
mention that by means of this canal 200,000 cubic metres of water, or
600 litres (a litre is about a quart) per inhabitant are brought to
Madrid daily. Of these 600 litres 100 per head is for domestic use,
and 500 for irrigating the districts adjoining Madrid. The quality
of the water is said to be excellent; indeed it is alleged that if
the air which it contains were abstracted it might be considered as
distilled water. The pressure of the water in the conduits is almost
without exception sufficient to raise it to the upper stories of the
highest houses in Madrid. In some quarters of the city it could rise 75
yards above them. There are two road tunnels in Spain, one on the road
between Grenada and Motril, 300 metres long, and one on the Pyrennean
road between Barbastro and Benasquez, the length of which is 90 metres.
Spain, for a country with a population under 16,000,000, cannot be said
to be badly off for means of communication. The total length of roads
in the kingdom on the 1st of January, 1867, was 4,137,640 miles of the
first class, 3,265,700 of the second, and 1,908,112 of the third. About
2,800,000 are in course of construction. It is intended eventually to
extend the road system of Spain to a total of about 22,500,000 miles.
As already mentioned, the total length of Spanish railways on the 1st
of January, 1867, was 3,182 miles.
There are few tunnels of any length in the United States. The
Cincinnati Tunnel is 3,337 yards long; the Kingwood 1,366. The
Alleghany mountains are perforated by one, the property of the
Pennsylvania Railroad Company, which is 1,204 yards long, 24 feet wide,
and 22 feet high. There are four through the Blue Ridge Mountains,
Virginia, the longest of which is 1,955 yards, the next 1,418 yards,
with an uniform gradient of 1 in 70. The Long Duck Tunnel, New Jersey,
is 1,437 yards in length. But the Hoosac Tunnel, Massachusetts, will,
when completed, be the longest railway tunnel in existence—except the
tunnel of the Alps—8,166 yards; it was commenced in 1855, but it has
only been vigorously proceeded with since 1864; its total estimated
cost is to be £1,100,000, of which about £420,000 have been expended
upon the 2,350 yards already constructed; its width is 26 feet, height
24 feet; the rock through which it is pierced is mica slate mixed with
a little quartz.[132]
General Haupt, of the United States Army, the engineer-in-chief of
this tunnel, is said, by the _Times_, to have invented one of the
most compact, effective, and economical drilling machines, applicable
for boring tunnels, driving adits of mines, and indeed for every
description of work in which the hardest kinds of rocks have to be
pierced. It is stated that it can drive holes in granite, or even
quartz, at the rate of nearly four inches in a minute, and that as
soon as about twenty-eight inches have been drilled, the blasts take
place, when the machine can, in consequence of its great lightness and
portability, be immediately carried over the _debris_ caused by the
explosion, and be at work upon the new face of the tunnel in the course
of a few minutes.
We extract the “latest novelty” in tunnels from a New Zealand newspaper
received in England August 1867,—
“A TUNNEL THROUGH AN EXTINCT VOLCANO.—The Moorhouse Tunnel, opening up
the fertile plains of the Canterbury settlement, is 2,838 yards long,
and cost £195,000. It affords, we believe, the first instance where
a complete section of an extinct volcano has been opened out. The
elaborate drawings prepared by Dr. Haas for exhibition in Paris, will
draw the attention of geologists to the fact, and doubtless afford
the greatest satisfaction to the scientific world. The rock in the
tunnel may be described as a series of lava streams and beds of tufa,
intersected by vertical dykes of phonolite. The lava streams consist
generally of scoria, overlaying a coarse pink trachyte, which passes
gradually through shades of grey, purple, and blue into a black finely
grained dolorite intensely hard and tough; the lightest and softest
rock being at the top, and the densest and blackest at the bottom.
Regarded from an engineering point of view, the work is considered
eminently successful.”
The New Zealanders are naturally very much elated at the completion
of this, to them, great and important work, of which the _New Zealand
Examiner_, a monthly journal published in London, and devoted
exclusively to the interests of the New Zealand settlements, thus
speaks in its August number:—
[Illustration: METROPOLITAN RAILWAY.]
“That perseverance which has commanded success for England in so many
fields has achieved another triumph in New Zealand. For six years
has a quiet, but none the less remarkable, work been going on in the
range of hills that divides Christchurch from Lyttelton. Possessed of
a splendid harbour, the Province of Canterbury has had to suffer ever
since its foundation from the difficulty of communication between its
capital and port. At first sight the range of hills appear impassable,
and are sufficient to frighten new arrivals. For the first years of
the settlement’s existence there was nothing in the shape of a road
until the track over the hills was widened into a bridle path. All
goods destined for Christchurch had to be sent round in boats up the
river. Then came the cutting of a cart road winding round the hills,
and eventually reaching Heathcote (which may be properly called the
Christchurch side of the range). The latter road was opened in 1859,
and ever since the traffic on it has continued increasing. In 1856 an
attempt was made to introduce steam navigation on the river, for the
quicker and cheaper conveyance of goods, this unfortunately terminated
disastrously in the wreck of the steamship Alma. The course of the
river having been staked out in 1858, the Planet commenced running,
and from that time the number of coasting steamers has steadily
increased, while the sailing vessels from being confined to craft of
15 to 20 tons have risen to 100 tons. Still the great desideratum of
a _direct_ and _rapid_ communication remained, and various schemes
were propounded, but none carried into effect till May 1861, when
the Provincial Government accepted a tender from Messrs. Holmes &
Co., to complete a line of railway from Lyttelton to Christchurch (a
distance of six miles) in five years, for £240,500. In this contract
the tunnel, 2,838 yards long (the cost of which was estimated at
£195,000), was included. The first sod of the line was cut on the 17th
July, 1861, and for six long years, night and day, has the process of
boring through the mountain gone on. During that time the contractors
have met with all sorts of difficulties, not the least of which have
been the attractions offered to their men by the successive outbreaks
of the Otago and Canterbury diggings, but, lending their whole
energies to the task, the works have not been stopped for a single
day. The completion of this work must be productive of the highest
benefits to Canterbury.
It will thus be seen that this tunnel cost at the rate of £69 per
yard forward, and it required six years to complete it at a cost
both of money and time very onerous to a young settlement. With Mr.
Fell’s system the tunnel would have been altogether avoided, and it is
probable that the line would have been completed in about two years, at
a price not exceeding £60,000, instead of the £240,500 it has cost the
colony to construct it.
The total length of London’s greatest tunnel, the Metropolitan Railway,
from Bishop’s Road to Moorgate Street, is 23,616 feet, or 4½ miles,
less 144 feet. Starting from Bishop’s Road, the measurements are as
follows:—For 3,024 feet, or 96 feet less than five-eighths of a mile,
there is tunnel, then an open space of 675 feet around the Edgware
Road station. From there to King’s Cross, 2 miles and 496 feet, is
tunnel; but in this distance there are three most effective means of
ventilation: the first is at Baker Street Station, 2,640 feet, or
exactly half a mile from the Edgware Road Station. The second is at
Portland Road Station, 2,978 feet, or 338 feet more than half a mile,
from Baker Street. Portland Road Station is the most open of all the
four intermediate stations. The third is at Gower Street Station, 1,920
feet, or 60 feet more than three-eighths of a mile. From Gower Street
to King’s Cross Station is the longest interval between two stations,
3,900 feet, or 60 feet less than three-quarters of a mile. The distance
between the King’s Cross and the Farringdon Street Stations is 5,192
feet, or 88 feet less than a mile. In this distance there are two
tunnels—if one of them may be so called, for it is only 220 feet long;
the other is 2,170 feet, or 190 feet more than three-eighths of a mile.
In the remaining 3,836 feet, or 124 feet less than three-quarters of a
mile, there are two little tunnels, one 523 and one 91 feet. During the
hours the sun is above the horizon, complete light is never absent in
the 91 feet tunnel—the train is no sooner in it than it is out again;
and in the longer one there is for a moment or so “a dim religious
light,” and then it is actual daylight. The amount of this, however,
must depend upon the season of the year at which the passenger goes
through it. In certain dark days of November it is hard to say which is
the darker of the two—the tunnel or the daylight.
The foregoing measurements will be readily understood by reference to
the diagram herewith appended. It is a section of the Metropolitan
Railway from end to end.
As regards its ventilation we shall speak presently.
[Illustration: SECTION OF THE METROPOLITAN RAILWAY. LONDON.
_Horizontal Scale_ 2000 ft—1 _inch_ _Engineer, John Fewler, Esq._
_Vertical Scale_ 40 ft—1 _inch_ _General Manager, Myles Fenton, Esq._
]
There are two railways in connection with the Metropolitan Railway,
which are also to be carried underneath portions of London. The
Metropolitan District Railway, when finished, will form the southern
side of the inner railway circle that is to encompass London. It
connects at Kensington, with the “Metropolitan Extension Railway”
(a continuation from Paddington of the Metropolitan Railway). This
extension is to run through Brompton to Pimlico, where it will be in
closest proximity to the Victoria Stations of the London, Chatham and
Dover, and of the London, Brighton and South Coast Companies; from
there to Westminster Bridge, whence it is carried along, and, in fact,
forms part of, the Thames Embankment, to Blackfriars Bridge. Here it
is again in close contact, although at a different level, with the
line of the London, Chatham and Dover Company, near its Ludgate Hill
station. Proceeding eastward, it is carried as far as Trinity Square,
Tower Hill, where it is to meet the eastern “Metropolitan Extension” of
the Metropolitan Railway. These two sections finished, the whole inner
Metropolitan circle will be completed. The distance from Kensington to
Trinity Square is 33,150 lineal feet, or 6 miles and 1,470 feet, of
which a little more than a third—that is, 10,974 feet—or 2 miles and
414 feet, are open cuttings or glass-covered stations, and a little
less than two-thirds, or 4 miles and 1,056 feet, are in tunnel. The
open cuttings and the tunnels are constantly alternating; the three
longest of the latter are 665 feet; one is close to Gloucester Road
Station, Brompton; one is at Tothill Street, Westminster; and the third
is in the Thames Embankment. The gradients are favourable, there being
only 2,352 feet (or less than half a mile) of 1 in 100, or 52 feet in
the mile. These are all situated between Blackfriars Bridge and Trinity
Square, Tower Hill. In addition to the foregoing main line of the
Metropolitan District Line, there is to be a railway from Kensington
High Street to join the West London Railway—the line that connects the
London and North-Western and the Great Western railway systems north of
the Thames with the Clapham Junction Station on the south. From Clapham
Junction there is unbroken connection with all parts of the London and
South-Western, and the London, Brighton and South Coast Railways.
The length of the Kensington and West London Extension of the
Metropolitan District Extension is to be 7,470 feet, or 450 feet less
than a mile and a half, of which 5,565 are to be entirely open, 525
station roof and 1,380 covered way.
The St. John’s Wood Railway, which starts from the Baker Street Station
of the Metropolitan Railway, is in tunnel throughout, and is a series
of stiff gradients, culminating with the stiffest of all at its St.
John’s Wood end. The line is 2¾ miles long, and its total rise in
this length will be 255 feet, but the elevations are very unequally
distributed. Starting from Baker Street Station, it proceeds for a
short distance on a level, and then it rises 1 in 90 and 1 in 44 to
the Regent’s Canal. From the canal the line descends slightly, and
then at three quarters of a mile from Baker Street will commence an
ascent of 1 in 60, or at the rate of 88 feet in the mile, for 660
yards. Then follows an incline of the same length of 1 in 150 (35
feet in the mile), then for 440 yards nearly level, except, just for
a few yards, 1 in 80. At one mile and 1,320 yards from Baker Street
commences a gradient of 1 in 27, or 196 feet in the mile for a length
of 1,320 yards. Half way up the gradient will be a station, but the
steepness of the gradient will be diminished for about 200 feet to 1
in 250, or 21 feet in the mile. Mr. John Fowler, the President of the
Institution of Civil Engineers, is engineer of the Metropolitan, the
Metropolitan District, and the St. John’s Wood Railway Companies. The
construction of an extension of this last-named line to Hampstead has
been authorised.
The longest tunnel in Europe _over_ land and over water is the
Britannia Tubular Bridge built across the Menai Straits, parallel to
and some mile and a-quarter from Telford’s beautiful Suspension Bridge
opened for road traffic in 1829. It is 1,834 feet 9 inches long, and
in fact consists of two independent wrought iron tubes, each placed
alongside of the other. There are four spans, two of 460 feet each,
and two of 230—that is, the tubes rest upon two abutments and three
towers of masonry—at an elevation of 100 feet above high water mark.
The tower called the Britannia Tower is built upon a solid rock that
projects above high water nearly in the centre of the Channel. The
summit of this tower is 130 feet higher than the level of the railway
in the tubes. The total weight of iron in the tubes is 9,360 tons, each
tube of 460 feet weighs 1,587 tons, each of 230 feet weighs 753 tons,
but these weights of iron are greatly in excess of what would be put
in tubular bridges of like spans at the present time; and for a length
but little exceeding a third of a mile, one tube, and not two, would be
considered more than sufficient for all traffic, in both directions,
that could be conveyed through it. The tubular bridge across the
Conway River, forty-five miles from Chester, consists of two tubes
placed alongside each other, each is 400 feet long and 1,180 tons. The
combined cost of the two bridges, Britannia and Conway, is always set
down at a million sterling. Now-a-days they would be constructed for
about half that amount.
But Canada, or rather the Grand Trunk Railway of Canada, can put
forward the boast that it possesses the longest over-land-and-water
tunnel in the world. The Victoria Railway Bridge is constructed across
the River St. Lawrence just above the ancient city of Montreal. The
entire length of this stupendous structure is 3,470 yards, or exactly
50 yards less than 2 miles. The tube is approached on each side by a
solid abutment, that on the north side being 266 yards long, on the
south 400 yards. Deducting these measurements from the total length of
the bridge, the tunnel or tubular portion of it is 2,804 yards long,
or 164 yards more than a mile and a-half. In addition to the abutments
there are 24 piers of masonry which it is impossible to exceed in
grandly massive strength and solidity. The current of the St. Lawrence
runs where the bridge is constructed at a rate never less than six
miles an hour, and in some parts of the stream its rate is ten. The
real giant force, however, which the piers have to resist is the ice
at its breaking up some time between the last ten days of each April
and the first six or seven of each May. The late Mr. Robert Stephenson
the engineer of this bridge, as well as those at the Menai Straits and
at Conway, estimated the ice pressure on some of the central piers of
the Victoria Bridge at six thousand tons each. It is therefore not to
be wondered that there is no stone opposed to the current at each of
these piers which weighs less than ten tons, and that all should be
clamped together by massive bars of iron drilled into each block, and
held fast for ever by molten lead poured into each interstice. The
total amount of masonry in the bridge is 3,000,000 cubic feet, or about
22,000 tons. There are 25 tubes or spans of which 24 are 130 feet long
each, and the centre, which is 60 feet above the surface of the water,
is 242 feet long. The total amount of iron in the structure is 10,400
tons. The contractors for the bridge were Messrs. Peto & Betts, their
resident engineer was Mr. James Hodges, and to him the chief merit in
connection with the construction is due. Its cost was £1,350,000. It
was opened for traffic at the period of the Prince of Wales’ visit to
Canada and the United States in 1860.
So far as regards tunnels actually constructed. We now come to speak
of tunnels suggested. These may he divided into two classes—tunnels
under rivers and tunnels under the ocean. Of the former, the first
to he mentioned is that proposed to he constructed under the Mersey,
to connect its Cheshire and Lancashire sides together. The scheme is
propounded by Mr. John Hawkshaw, the eminent engineer, in a letter
which he addressed to the Mersey Dock and Harbour Board, on the 31st
of August last. Mr. Hawkshaw having stated that it is evident a bridge
or viaduct over the river would interfere with the navigation, whilst
the sand-stone rock which underlies its bed affords facilities for the
construction of a tunnel, proceeds to show that the river should be
crossed between New Brighton and Bootle, that being the best point for
connecting together the dock lines of railway on each side of the river
Mersey.
The cost is set forth as follows:—
Total length of lines 9¼ miles; length of tunneling, 4,800 lineal
yards: estimated cost £785,000.
The lowness of the estimate is owing to it not being necessary to
pass through valuable property, or important commercial buildings of
any kind. Nevertheless Mr. Hawkshaw feels that the usual allowance
for contingencies should be increased from 10 to 20 per cent. on the
outlay. Still it brings the total amount considerably under a million.
Mr. Hawkshaw does not ask the Mersey Docks and Harbour Board to be at
the total cost of these works, however important it is that the two
several portions of the board’s establishment should be closely united
in the manner which this tunnel accomplishes, but that it should only
contribute a portion of the outlay—an outlay which he considers will
not be more than a third of what will be required for accomplishing
any other of the schemes that have been proposed for carrying a tunnel
under the Mersey.
In 1864 the Dublin Trunk Connecting Railway obtained an Act for the
construction of a railway in the immediate vicinity of Dublin. Part of
the plan sanctioned by Parliament is a tunnel under the Liffey, less
than half a mile from its mouth. The depth of the tunnel-top under
the bed of the river will be 20 feet. The stratum of limestone rock
is curiously placed where the tunnel is to be pierced. The bottom of
it will rest upon the rock, but the tunnel itself will be constructed
through the superjacent clay. It will be lined with brick in cement.
Its length under the river is to be 324 yards, and the approaches to
it, which are to be constructed in the manner known as “cut and cover,”
are to be 430 yards each. The gradients on both sides will be 1 in 70,
or 75½ feet in the mile. The cost is estimated by Mr. John Burke, the
engineer for its construction, at £200 per yard forward.
A proposal has recently been made to construct a tunnel under the
Humber from Barton to Hessle, close to Hull. A bridge over the river
has often been spoken of; but its estimated cost, £700,000, render its
construction hopeless. It is considered that the tunnel, which would
be about 2,000 yards long, could be constructed for £150 a yard, and,
with an allowance of £50,000 for approaches, the total cost would
not exceed £350,000. It is not probable, however, that the railway
companies concentrating on both sides of the river would find it to
their interests, at all events at present, to carry this project into
execution. The company that would most benefit by it would be the
Manchester, Sheffield and Lincolnshire.
Mr. Peter W. Barlow, civil engineer, has recently obtained permission
from the City Commissioners of Sewers to construct a subway beneath
the Thames, which is to be carried from Lower Thames Street to the
opposite shore of the river. The dimensions of the subway are to be
sufficient to allow a loaded omnibus to pass through it. If constructed
economically, there is no reason why it should not answer commercially.
We perceive by recent accounts from America that it was originally
intended to connect the railways concentrating on both banks of the
Mississippi at St. Louis, by a tunnel under the bed of the river; but
this plan has been abandoned, and instead of it a “sub-aqueous iron
tubular bridge” is to be laid on the bed of the river, which is about
half a mile wide in this vicinity.
The difficulties connected with crossing the upper Indus at Attock, a
thousand miles from its mouth, and 940 feet above sea level, have long
been felt. Colonel Robertson, of the Madras Staff Corps, therefore,
proposed a scheme for going under instead of over it. In his report on
the subject submitted to Government in 1859, he stated that, as the
geological formation at Attock, is a compact slate rock, it is easily
worked; and under the bed of the river it is apparently not broken by
any great fissures which might possibly endanger the tunnel. Colonel
Robertson fixed the upper level of the excavation for the tunnel at
60 feet under low water cold weather mark, or, at the water’s deepest
point, 20 feet below the bed of the river; the lining of the tunnel to
be 2 feet thick, and as its height is 20 feet, the foundation level
would be 82 feet below the low water level. To guard against all risk
of inundation through floods, which raise the level of the river from
50 to 92 feet (it was at the latter height in 1841), the two entrances
of the tunnel are to be 100 feet above low water level. The width of
the river at the point selected is 1,215 feet. This portion of the
tunnel is to be nearly on the level; but the gradient of the approaches
to it on each side, each 3,720 long, is to be 1 in 40, or at the rate
of 132 feet in the mile; the total length of actual tunnel to be 7,215
feet, as some portion of each approach is to be in open cutting. There
are ten shafts, each 600 feet apart, except at the actual river, where
they are 1,580 feet apart. In 1860 the works were commenced, and a
drift gallery had been nearly carried through, when all operations were
suspended; but it is intended that they be resumed in prospect of the
railway between Lahore and Pesshawer being constructed. The revived
estimate makes the cost of the tunnel £105,000, if the gradient on each
side be 1 in 20; but if it be flattened to 1 in 30, the estimate is
£143,300.[133]
The greatest tunnels that we know of connected with mining
(irrespective of galleries for working in mines) are the great drainage
galleries at the mines of Clausthal, in the Hartz, 11,377 yards, or
6½ miles long, and in many parts 900 feet below the surface of the
superjacent mountain. The second is the _Great Adit_, which drains
several of the important mines in the parish of Gwennap, Cornwall. It
is from 30 to 60 feet below the surface, and is 30 miles long. There is
an adit level of 10,000 yards to the celebrated silver-mines of Norway.
There are two modes by which it is proposed to carry a subway between
France and England,[134] the first is by means of iron tubes laid on
the bed of the ocean, the other is by actual tunnel. At the present
time no less than three competitors present themselves for the honour
of constructing the former, and there is only one whose scheme is
before the public for the latter. The three advocates for the tubular
system are Mr. James Chalmers, Mr. B. Hilmer, and M. Thome de Gammond,
of Paris. Each has his mode of laying down and connecting the tubes
together, but the great and distinguishing feature of the plan of M.
De Gammon, is that he proposes to construct a great oceanic station,
which is to be a kind of half-way halting house between the two shores.
Here also is to be a harbour and three ship’s basins, so that any one
returning from a long voyage and being in a hurry to get either to
London or to Paris, or to any other place—it signifies not where—in
England or the Continent, might land and at once proceed upon the
_terra firma_ portion of his journey. In the centre of the harbour
there is to be a huge shaft 330 yards in diameter, which would serve
the double purpose of ventilating the tunnel, and of providing means
of ingress and egress between the _Islet de Varne_ station and the
upper and outer world. All these great advantages—tunnel, shaft, and
railway—are to obtained at the cost, as estimated by M. De Gammond, of
£7,200,000!
[Illustration: SECTION OF
CHANNEL RAILWAY TUNNEL
AS PROPOSED BY M^R. GEO. REMINGTON C.E.
From “Engineering” #/ ]
The advocates for the tubes insist that theirs is the right system,
in consequence of its having been publicly stated that Mr. Hawkshaw
has satisfied himself by many borings that the bottom of the English
channel between Dover and Cape Grinez, has too many and too deep
“faults” to permit of tunnelling. Mr. George Remington, C.E., however,
considers he gets over the difficulty by avoiding the line originally
selected for the Anglo-French tunnel. He therefore proposes Dungenness
as his English starting point. The depths of the tunnel is, says Mr.
Remington, to be from 90 to 130 feet below the bed of the channel,
and there are to be three main shafts, the first at the point of
Dungenness, the second on the shoal in mid-channel, where there are
only eleven feet at low water spring tide, and the third at Cape
Grinez. These shafts are to be 100 feet diameter, and being carried
up considerably above the sea are to act as lighthouses. It would be
inconsistent with the character of this work to enter into an account
of the technical details which Mr. Remington proposes to adopt. We
shall, therefore, limit ourselves to saying that in addition to the
three intended permanent shafts, it is likewise proposed to put down
ten temporary shafts, the cost of each of which is not to exceed
£20,000. With these thirteen shafts, says the editor of _Engineering_,
“the tunnel may be carried on in twenty-six sections, and the distance
from shore to shore being twenty-six miles, gives only one mile for
each section, or two miles for a shaft, and assuming an advance of only
one yard a day for each headway, the whole distance may be accomplished
in about five and a-half years,” exclusive of the couple of years
required for sinking the shafts.
The following is Mr. Remington’s estimate:—
56,320 yards run of tunnelling of £100 £5,632,000
Three main shafts, at £50,000 150,000
Ten temporary shafts, at £19,800 198,000
Six miles of approaches, at £20,000 120,000
36 miles of permanent way, at £4,500 162,000
Stations 100,000
———————————
£6,362,000
Contingencies 636,200
———————————
Total £6,998,200
Is it practicable? An excellent authority, although, no doubt, a little
of the “go-a-head” class, says, “Yes,” and informs the world that
there is judicious “provision for gas lighting, water pipes, electric
telegraph and proper drainage, and indeed all that can be desired to
make the passage through the tunnel as safe and comfortable as transit
on the Metropolitan Railway.” On the other hand, there is the opinion
of Mr. Hawkshaw, whose borings we have just referred to. Have they
been extended as far to the westward as the diagonal line, or course,
proposed by Mr. Remington, and do the “faults” extend to a depth of
from 80 to 130 feet below the bed of the ocean? At all events, thinking
it would interest our readers, we have had engraved the section of
the tunnel from the drawing of it, which was recently published in
_Engineering_, and it is herewith inserted.
There is no incident or occurrence in life, no matter how solemn or
serious it may be, that cannot, in some way or another, contribute
to travestie and amusement. We shall therefore, conclude our notice
of “Tunnels suggested,” with the following piece of pleasantry
extracted from a recent number of the _Scientific American_—“A gigantic
engineering project is now the sensation out West—a tunnel under the
Atlantic for a railway! The plans are already supposed to be drawn up,
complete in detail. Even to lighting the cars with the magnesium and
electric lights. The undertaking is to employ one hundred thousand
men for thirty years, and when completed it will take the trains
but five days to do the journey from Newfoundland to Ireland, _viâ_
the telegraph route. The amount of capital required is estimated at
two billions five hundred million dollars.” Well may the Editor of
_Engineering_ lift up his hands and exclaim, GOOD GRACIOUS!
[Illustration: THE MONT CENIS TUNNEL RAILWAY
LONGITUDINAL SECTION]
[Illustration: SECTION OF THE
MONT CENIS RAILWAY
JAMES BRUNLEES ESQ^R. ENGINEER.]