Chapter XII: Tunnels, Ancient and Modern (2)

“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.

_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!

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!

LONGITUDINAL SECTION]

MONT CENIS RAILWAY

JAMES BRUNLEES ESQ^R. ENGINEER.]