Chapter XII: Tunnels, Ancient and Modern (1)

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:—