CHAPTER VII

_THE TUBULAR SYSTEM_

“Thy arts of building from the bee receive; Learn of the mole to plow, the worm to weave.”--POPE.

ORIGIN OF THE SYSTEM

Last year there were sounds of strife in that financial atmosphere where dwell Titan capitalists, who think and talk and dream in millions; a battle of giants, like the conflict imagined by Milton, when the satanic host levelled “triple-mounted rows” of deadly tubes with such effect against seraph and seraphim, “that whom they hit none on their feet could stand, though standing else as rocks.” But the conflict now past, concerned tubes of another kind--iron railway tubes, that seem to be the destiny of underground metropolitan travellers. The Morgan group, the Yerkes’ combination, and other great coalitions, mustered their battalions for the fray. The London County Council, following the policy of Lord Stanley’s army at Bosworth field, hovered aloof ready to take advantage of the defeat of either; the Corporation of London anxiously watched from afar; the great suburban railway companies shivered in their shoes; a parental Legislature held the balance impartially between the combatants; while the people whom the matter most concerned--some six millions of Londoners--had to sit down with folded hands and, patiently or impatiently, await their fate.

Recollecting this tangle and uproar of conflicting interests, it behoves everybody to have some notion of the subject of the Tubes and their construction.

Like many other things in the world, there is nothing new in the idea of boring a hole through the earth and lining it with brick or iron. As Pope suggests, mankind doubtless learnt the art from Nature, though the correctness of the poet’s zoological knowledge is hardly shown in the examples heading this chapter. For ages past--before London existed--that skilful excavator, the mole, tunnelled through the earth, making roads and galleries, the friction of his fur, set perpendicularly on his skin, lining his tube so that the soil did not fall in. The larvæ of the humble caddis-fly covered the inside of their cases with fine silk; and the trap-door spider lined its 12-inch long shaft with similar material to prevent the tumbling in of loose particles and to afford itself a foothold in climbing up; while the ant constructed her galleries and stuccoed them with the finest grains of soil, so that the inner walls presented a smooth, unbroken surface.

With the advent of man and his civilisation came the extensive use of furs, and in these the grubs of the moth--in the abstract the most engaging of creatures--made galleries whenever they got a chance, lining them with their own silk, wherein to undergo their transformation into the pupa stage.

Well-experienced engineers, such as the vine, beech, pine, and bark-boring beetles, are all tube-makers; but it is the pholas, or _teredo navalis_, who is the arch-borer, so skilled an expert in lining, that, though only the size of a quill and “soft in body,” he pierces the hard timbers of ships and quay-piles, lining the tubes as he proceeds with a saliceous substance as hard as china. The body of the Teredo is like a long white worm, varying from a foot to two inches and a half in length, and about the width of a finger. From him, it is said, the elder Brunel took his idea of the shield which he employed in constructing the tunnel beneath the Thames after the shaft had been excavated.

But his clever system was crude, and not calculated to cope with porous or aqueous soil; therefore, when the stratum of clay, through which the work was being carried forward, broke off abruptly, a serious influx of water took place. The work had to be abandoned, and was only completed after much delay and ruinous expense. In a commercial sense, it was an utter failure.

Since Brunel’s time, engineering has developed its resources _pari passu_ with the development of science. Hydraulic force displaces the primitive screw power, and steel plates the cumbersome timber works used in the Thames tunnel.

Tunnelling through rock, like the Mont Cenis and St. Gothard mountains, is a comparatively simple engineering feat, as no lining is required; so also is the ordinary railway tunnel, carefully bratticed and propped inside, and securely cased with brick or stone. But it is, as the Great Western Railway knows to its cost, in dealing with water-bearing strata, _vide_ the Severn Tunnel, that a system is required, not only to protect the men as they bore with a gigantic centre-bit through clay, chalk, or gravel, but, pholas-like, to line the tunnel simultaneously. This is obtained by the use of the famous shield invented by the late Mr. J. H. Greathead, and employed by him in the construction of the City and South London and Waterloo and City Railways, though he did not live to witness the adoption of his principle in the Twopenny Tube.

RAILWAY TUBES, HOW THEY ARE BORED

A revolution in tunnelling has been brought about in constructing Tube railways. By the new process a great cylinder or shield at the bottom of a shaft is pushed forward by hydraulic power into the soil ahead of it. The navvies work inside, excavating the earth in front of them, and fit up iron segments at the rear of the tail end of the cylinder, or shield. Thus, on the one hand, the exact size and shape of the tunnel is ensured, and the workers are fully protected from the risk of the roof falling in.

This arrangement of shield and iron tube resembles an old-fashioned single-drawn telescope; the outer case being the shield, and the inner tube the lining of the tunnel. These shields have fronts that bear a row of steel knives forming a true cutting edge, and are so arranged that they can, if required, bore a circle slightly larger than the iron segments of the tube. As the shield slides away from the inner tube, the space it occupied is filled in with what is called “grout,” a kind of porridge of water and lime, which soon sets as hard as stone. This is ingeniously blown in through apertures in the iron lining by means of compressed air, and effectually fills up cracks accidentally formed in the soil, which might otherwise extend to the surface and cause subsidence in the foundations of buildings. Theoretically, therefore, no disturbance of the ground below or above the tubular lining is possible.

In the pioneer Tube railways, the City and South London for instance, the diameter of the tunnels was only 10 feet 6 inches, that of the Central 12 feet, but the Great Northern and City Company made a new departure by fixing the width at 16 feet. For the construction of this railway, the shield was designed by Mr. E. W. Moir, M. INST. C. E., and varies in some important respects from the Greathead shield. A remarkable photograph, which, by the courtesy of the _Tramway and Railway World_, I am able to present to the readers of this book, shows this shield at work in the construction

of a running tunnel, 16 feet in diameter, on the above line. The Great Northern shield is much more powerful than any hitherto employed. Greater hydraulic force is applied, and the “jacks” are more numerous, and considerably larger. The shield used for the sixteen-foot tunnel may be taken as typical of others up-to-date. Its cylindrical skin is composed of half-inch steel plates riveted together at the bottom of the indispensable shaft, which may be, in the future, anything from 50 to 500 feet beneath the surface. In length, the shield from the rear to the cutting edge in front is 8 feet 9 inches, half of this being used by the excavators (as in Brunel’s Thames tunnel), the after part for the erectors of the metal segments of the tube. Round the shield front are mounted ten heavy cast-steel cutters, the pressure upon them being no less than two tons to the square inch, the hydraulic rams exerting this pressure direct upon the back of the cutters, and the purchase is taken off the edge of the nearest tunnel segment already in position. The excavated soil is taken away in trolleys, which, as in a mine, are drawn by ponies on a miniature track, and afterwards sent up to the surface by the nearest shaft.

London clay is generally the kind of soil thus bored through in the metropolitan tubes. The Central, while sinking the shafts, met with it 29½ feet below the surface; but before this was reached, 12 feet of made ground, 18 inches of loam, and 16 feet of gravel, had to be pierced.

The London clay ran almost without a break between the Bank and Shepherd’s Bush, the only hiatus being at a point between Red Lion Street and Berner’s Street, where the Woolwich and Reading strata cropped up, which proved to consist of hard, red, streaky clay, some beds of white sand, and, strangely enough, beds of hard limestone rock, whose presence had not been anticipated.

Tube railways are carried out at considerably varying depths; the Central running in places 100 feet (_i.e._ the height of Westminster Abbey’s nave) below the road, and at the Bank only 65 feet.

Some of the proposed tubes burrow much deeper; for instance those of Charing Cross and Hampstead Railway will be from 120 to 216 feet below the surface. Apparently, there is no reasonable limit to the depth at which engineers are prepared to lay their railway tubes.

THE TUBE MOLE AT WORK

By an instinct--the heritage of years--of a kind that prompts gamekeepers to slaughter indiscriminately eagles, hawks, crows, magpies, owls, and even squirrels, classing them with such vermin as pole-cats, stoats, weasels, and rats, ignorant farmers and gardeners wage war against the mole, asserting that in driving his tunnels he throws up unsightly heaps of soil, and, worse still, loosens and destroys the roots of plants and grass, totally ignoring the fact that Mr. _Talpa Europæa_, though he may occasionally disturb the earth around, acts as a very efficient surface drainer, and still better, is a persistent chaser and devourer of his natural prey, the wire-worm, and other injurious insects.

Our Tube mole throws up no hillocks, but he is accused of being the source of much mischief, and of endangering the houses on the surface--damaging, as it were, their roots--by the vibration arising from the continual passage of trains along the iron galleries and the consequent subsidence of the ground. This has given rise to numerous complaints, so pronounced as to become the subject of an official inquiry.

Some foolish objections have been raised to deep-level railways, and equally unreasonable claims for injury done by them have been brought into court. Where a vibration clause is inserted in any Tube Railway Bill, there might be ingenious claims manufactured for compensation. For instance, a watchmaker might come forward and say that the vibration caused by the railway prevented him from setting his chronometers, or a wine merchant might say that his wines were shaken up; and in this way the company might be subject to endless litigation.

When it was proposed to bore tunnels 70 feet below the royal demesnes of Hyde Park, St. James’s Park, and the Green Park, and as much as 216 feet below Hampstead Heath, approximating in the former case to the height of Queen Eleanor’s memorial at Charing Cross, and in the latter to that of the twin towers of Westminster Abbey, it was at once urged by the representatives of a certain Preservation Society that the trees, plants, and flowers of the three parks would be detrimentally affected by the Tube, and that the Hampstead Heath tunnels would “very probably drain the upper surface of the soil and destroy vegetation all round.” To which unthought-out contention Mr. R. E. Middleton, a well-known civil engineer, replied that “at the depths proposed for the parks the tunnels were to be constructed through a stratum, not of loose soil, but of stiff London clay, so that any question of destroying trees, plants, or flowers was rather absurd; in fact, vegetation would in no way be affected.” He might have added the argument that, although ordinary railway tunnels abound, no one had ever heard of the overlying fields and woods being deleteriously affected by them.

CLAIMS FOR DAMAGE BY TUBING

Now, in dealing with the matter of alleged injuries to buildings from vibration set up by Tube railways, I quote the following case to show how visionary are some of the claims brought against Tube Companies.

On the 14th of October last, at the Lambeth County Court, an action was brought against the Great Northern and City Railway Company by an individual living in Hoxton for damage alleged to have been done to his premises by the construction of the tunnels. The plaintiff stated that in consequence of this the repairs of his house had cost him £62, and that in another house of his, cracks had appeared. A photograph, taken twelve months before the tunnels were made, which showed a crack in front of one of the houses, was pointed out to the witness, who said that he had never noticed it.

For the defence Mr. Douglas Young stated that he acted for the Company when the tunnels were about to be constructed, and, anticipating claims of this nature, he caused photographs to be taken of all houses which showed cracks on the line of route. The cracks shown in the photos then taken were practically in the same condition now. The repairs necessary were not caused by damage done by the tunnels, and came entirely within the repairing clauses of the leases. The jury returned a verdict for the defendant Company on the ground that no damage had been done by them.

On the other hand, among the Tube Railway cases brought into court last year and this, was the following, which illustrates the contention that though there may be a certain amount of truth in the plaintiff’s arguments, exaggerated ideas prevail as to the sums that can be claimed for injury, present or prospective. It also shows the uncertain state of the law on the subject of ownership of the subsoil--a hard legal nut.

In the London Sheriff’s Court, 17th April, 1902, Mr. Under-Sheriff Burchell sat, with a special jury, to consider a claim for compensation brought by Mr. William Howard, of 11, Cornwall Terrace, Regent’s Park, against the Baker Street and Waterloo Electric Railway.

Mr. Morton, K.C., said that in August, 1900, Mr. Howard became aware that a subsidence was taking place, and that the walls of his house were cracking, this being unmistakably due to the borings for the railway which were being made underneath the property. In the course of these borings the Company had taken away part of the subsoil of the claimant’s premises without having given notice to treat, and this, counsel submitted, constituted a distinct trespass. The value of the property, counsel contended, had been deteriorated to the extent of at least £50 per annum. Mr. Howard’s lease had ten years to run, the rental being £200 a year.

After expert evidence had been given, the Hon. A. Lyttelton, K.C., for the railway company, said it was ridiculous to assert that the Company had committed an act of trespass. They disputed the claimant’s alleged ownership to land sixty-five feet below his premises, and were determined to fight the question in the courts, inasmuch as it was one which affected the whole of the electric tube railways in London.

One witness called on behalf of the Company said that the damage to the property could be remedied by the expenditure of a ten-pound note.

The Under-Sheriff said that an important feature of the case which the jury had to decide was whether the claimant was the owner of the subsoil. As such he would be entitled to compensation for any vibration that might occur when the railway commenced to run in about two years’ time. He left it to the jury to decide their verdict under two heads, namely, “what damages had at present been sustained,” and, “what damage was likely to accrue through vibration.”

After a brief deliberation the jury awarded £357, in one sum, as damages.

On the 6th of February of the present year, before Mr. Justice Ridley and a special jury, the hearing was resumed of the case in which Mrs. Dawson, a widow, carrying on the business of a draper at the junction of City Road and East Street, sued the Great Northern and City Railway for £10,000 damages, alleged to have been caused by the tunnelling operations in the vicinity of her premises. The claim included some £4,000 which it is estimated it would cost to put the buildings in a proper state of repair, and £5,000 representing loss of business during the time it would take to complete the work of reinstatement.

The jury returned a verdict for the plaintiff under the following heads: Amount for taking the subsoil occupied by the tunnel, £50; structural damage, £2,000; damage to trade and stock, £2,100; total, £4,150.

Mr. Dobb asked that judgment should be entered.

Mr. McCall thought the judge had no power to enter a judgment of the High Court because the proceedings were in the form of an interpleader action.

Mr. Justice Ridley said he would give judgment in the sense in which the word was used in the Lands Clauses Act.

Judgment was given accordingly.

At a meeting of the Auctioneers’ Institute held last year, Mr. G. M. Freeman, K.C., speaking on this subject, pertinently remarked that various questions were likely to arise between the promotors of the new order of underground railway and the owners of adjacent property, and he gave it as his opinion that the assertion that no possible damage would be caused, had not been wholly verified, and that the rights of compensation to persons equally injured ought not to depend upon whether a piece of the subsoil under the street was or was not appropriated. In his judgment, all owners who could prove damage done by the construction or working of an underground railway, should have the same title to compensation.

VIBRATION

The outcome of the Board of Trade inquiry last year into the vexed question of tube vibration was interesting. It showed that alleged annoyance from vibration has not been altogether imaginary, and some novel facts were produced. Fourteen meetings were held, and evidence was given by some of the residents along the line of the Central Railway route, their habitat ranging from Bucklersbury in the City to Kensington Palace Gardens in the west. A large number of the witnesses represented householders having “frontages,” and among others, the Holborn Borough Council. They all deposed as to annoyance caused by the vibration, and were of opinion that the shaking was most perceptible when the trains first began running in the morning; between five and eight p.m.; and shortly after midnight, just before the trains ceased running.

Had any of these gentlemen resided on the north side of Victoria Street, near its western end, they would hardly have complained about mere vibration. In that delectable locality the backs of the houses overlook the Metropolitan District Railway, and if the dining-room happen to be in the rear, as in many of the flats it is, every wine-glass and tumbler on the table quivers in a fearful manner, all the ornaments tremble, and the whole apartment is agitated as each train thunders by.

But even this is nothing, contrasted with the daily experience of dwellers in suburban side streets, where passing of steam-rollers, pantechnicon-vans, and other elephantine vehicles, not only shakes the tenements to their basements, but forces out the mortar that is supposed to bind together the brickwork, dislocates the window-frames, turns askew the pictures on the walls, and would eventually, if not seen to, reduce the “eligible villas” to ruin.

However, the Board of Trade Committee, as in duty bound, personally investigated the Tube complaints and satisfied themselves that vibrations, sufficient to cause vexation to the inmates, were really felt in some of the houses near the Central, and the result of the inquiry was as follows:--

That it was a matter of chance whether any given train caused a slight, or a severe, vibration; also that trains which produced much _tremblór de tiérra_ in one house, as likely as not caused but little in another, and that apparently different apartments in the same residence were not similarly affected by one and the same train. It was demonstrated that the locomotives, and not the cars, were responsible for the greater part of the disturbances, the reason assigned being that too great a springless load was carried on each axle of the engines, a method of construction adopted to obviate the necessity for gearing.

Acting upon the Committee’s representation, the Central Railway Company ordered two new types of locomotives, in one of which the “unspring-borne” load was much reduced by gearing. The other was not distinct from but attached to the train, the motors being carried at one end of two or more coaches--the motor-car system of electric traction in fact. The difference in weight was remarkable; the original gearless engines being 44 tons, the new geared pattern 33 tons, while the motor-cars only came up to 20 tons.

Some novel experiments were made, and in order to identify the trains, the houses in which the observers took their places with recording instruments were connected by telephone with the signal-boxes at the adjoining stations. Quite satisfactory were the results, and it was found that, during some two hours, the passing of every train drawn by the heavy gearless locomotive was distinctly felt, but was not discernible when the new engines were attached. Therefore the Committee concluded that, so far as the Central was concerned, the adoption of motor-cars would so reduce the _tremblement de terre_ as to cause all real annoyance to cease, though the sound of the trains, particularly at night, might still be detected. As to the oscillation of the cars--a rather marked feature in the Tube--it was attributed by the Committee’s experts to the unevenness of the surface of the rails. As these leave the rolling-mills they are usually slightly curved, and the process of straightening them _in situ_, however skilfully carried out, inevitably leaves a certain amount of waviness. When the speed is high, a condition of things soon arises whereby the irregular impulses produced by the uneven rail surfaces establishes a rocking movement of the rails and the road-bed, converting both into an elastic instead of a rigid support. This is increased and maintained by the pounding of the gearless locomotives in the narrow tubes, intensified by the hard unyielding material of which they are composed.

Another fact to which the Committee called attention was, that in consequence of the small diameter of the tunnels (12 feet), the fit was too close, and the pressure in front of the trains necessitated greater power to overcome it than if more space had been left between the roofs of the carriages and the tubes.

In the agitation respecting damage alleged to have been done by the construction of the Tubes, it was proved that provided the apertures are made of sufficient size, and suitable locomotives used, and the permanent way properly laid with stiffer and deeper rails, the chance of injury to houses by the _moviéndo la tiérra_, as the Spaniards call it, can be reduced to a minimum.

Modern science tells us that earth tremblings are with us at all times and in all places to an extent not realised. We are assured that, by Professor J. Milne’s instruments, quiverings, and slopings of the earth’s crust, insensible to the most delicate spirit-levels, can be detected. It is now known that earthquake movements can be felt right through the earth, and all round its surface. Latterly, Professor Milne has also discovered that his observatory in the Isle of Wight sinks slowly during a part of the year, and rises as slowly during another part--as if the breast of the earth were heaving. For five months in the year, the tall buildings in a city may be heeling over towards the west; then they come back with extreme slowness to the perpendicular, and finally cant a little to the east.

Surely, then, we need not complain about an occasional mild earth-shake produced by the passing of the useful Underground, or Tube trains, seeing that the good they do so far outweighs their defects.