The Story of Brunel’s Great Engineering Feats in Linking up London and the West
ONE OF BRUNEL’S TIMBER VIADUCTS IN CORNWALL, SINCE REPLACED IN STEEL
IT was the success of the Liverpool and Manchester Railway which was responsible for the projection of a means of connecting Bristol to London by the steel highway, as a faster alternative way of communication to the circuitous canal route then in vogue. Directly the suggestion came before the public it received the inevitable hostile criticism, because the projectors were treading on the toes of scores of other interests, who viewed the Stephenson invention with undisguised disfavour.
The scheme languished for many years, until at last in 1832 a strong influential committee was formed to carry the idea into effect. This commercial body knew nothing about the technical problems involved. and they east about for an engineer. Among the aspirants was that engineering genius Isambard Kingdom Brunel, then only twenty-
Although the promoters only intended to connect London with Bristol, they failed to secure the necessary support. Accord-
A FAMOUS “FLYER” OF THE BROAD GAUGE ERA
In his constructional work Brunel was harassed by some of his controlling associates. He did not progress so rapidly as they desired. On more than one occasion he was within an ace of being superseded; proposals to bring in George Stephenson to straighten matters out were made frequently. When the line was opened it proved sadly lacking in many constructional respects, and there is no doubt but that for the unswerving support extended by one or two of the directors, the young engineer’s connection with the railway would have terminated abruptly.
As events proved, Brunel made a big blunder in the very beginning. Stephenson had adopted what is known now as the standard gauge, viz. a width of 4 feet 8½ inches from centre to centre of each pair of rails. This has been designated as a clumsy, haphazard decision, but Stephenson appears to have been content with what satisfied the world as he found it. The existing vehicles using the high roads, lanes, and tramways of the mines in the north had a certain gauge. Stephenson naturally carried out his experiments on this gauge, which eventually came to be adopted for the railways built shortly after his invention had proved its worth. The standard gauge often has been assailed as too narrow, but the mistake was not
Stephenson’s by any means. He merely adapted his radical revolution to existing ideas.
On the other hand, Brunel considered this gauge unsuited to high speed, carrying capacity, and safety. So he elaborated a gauge of his own, 7 feet, 0¼ inches, and strangely enough this was adopted for the Great Western. Certainly he justified his contentions, but they afforded no argument.
The “Battle of the Gauges”
There is no doubt that Brunel was supported in his gauge ideas by the desire to create a monopoly for the Great Western. In the early days of of the railway building the country was divided off into zones, and the concerns interested in railway transportation agreed to respect certain boundaries. Interchange of traffic was the last thought entertained -
Brunel’s Great Grade
But if Brunel proved to be in error in regard to the question of gauge, he was far more perspicacious concerning the over-
The first 23 miles of the railway out of London were completed to Maidenhead in 1838. It was a badly-
The following instances afford some idea of the quaint opposition which railway projects received in those days: The town of Maidenhead rose up in arms against the railway because it approached their boundaries too closely. On the other hand, Windsor became fiercely hostile because it left them too far to one side. Eton College regarded the line with deep-
SLIPPING TWO COACHES OFF THE UP AMERICAN MAIL WHILE TRAVELLING AT 60 MILES PER HOUR
The River Thames offered the first serious obstacle to the western advance of the railway. At this point the river is some 207 feet in width, and divided near the centre by a shoal. As the banks are somewhat low, and the gradient is maintained on either side, Brunel was somewhat hampered in his design so as to not encroach too much upon the headroom for navigation. He decided to introduce two main spans, each of 128 feet, and with a very flat elliptical arch. Brick was selected, and the work ranks as one of the largest structures of its kind ever attempted in this constructional material. Its erection, however, was not free from incident. The contractor, no doubt harried somewhat by the powers above, took away the centres too soon, with the result that a deformation set in. The administration, after Brunel had made an inspection, held the contractor responsible for the damage, and compelled him to repair it. In the meantime the most extraordinary stories relative to the incident had been circulated, and it was only with difficulty that the anxiety of the shareholders was allayed.
By March, 1840, the original proposal was completed; the line was opened to Reading, and in the same year the Bristol to Bath section was finished. Without any delay the line was continued from each end so as to close the gap in the comm-
The original line, forming the basis of the Great Western Railway, always has been famous for the high running speeds attained thereon. Certainly the location and alignment are conducive to this result. Between the two points the railway only has to rise to a matter of 270 feet above the metropolis, and then drop 292 feet into Bristol. Of the 118 miles no less than 67 either are level or rise only 4 feet per mile, while another 17 miles have grades ranging between 4 and 8 feet per mile. The remaining section is made up of the two short banks, rising 1 in 100, against eastbound traffic.
As may be supposed, while this railway was under construction, further lines in conjunction therewith were projected and carried into effect. An obvious extension was from Bristol to Exeter, built by another company and opened in 1844. In due course came the South Devon and Cornwall lines. The various sections being in connection, it was possible to travel by rail from London to Plymouth and beyond. When the Great Western Railway had become firmly established, a policy of absorption was followed, so that slowly but surely innumerable short links were bought up and amalgamated with the parent concern. Under this policy the company became entrenched firmly throughout the south-
THE AMERICAN BOAT EXPRESS LEAVING FISHGUARD FOR LONDON
Through railway travelling between London and Cornwall was broken at Plymouth by the broad Tamar, which at this point is
1,100 feet wide, with a depth of 80 feet at high water. At first the obstacle appeared to be so formidable that a steam ferry was projected, but at last it was realised that a bridge was the true link of communication, and a point at Saltash was selected for the crossing. A design was prepared, to be executed in timber, having one span of 225 feet, and six spans each of 105 feet. Doubtless this project would have been undertaken had the Government not interfered. Devonport naval base is close by, and the Admiralty insisted that the waterway should be kept clear, that at least 100 feet of headway should be provided, and that there should be only five spans.
Faced with this irreducible minimum Brunel evolved a startling design. The bed of the Tamar is somewhat unstable, and the building of piers in deep water always is a costly and tedious proceeding. Brunel boldly decided to introduce only two main spans, thereby reducing subaqueous work to one pier in the channel. This entailed two big spans, each of 455 feet. The foundations and under-
Alter considerable reflection the engineer decided to build the pier upon the caisson system, although it involved a huge structure and operations upon a scale which never had been attempted up to this time. The massive cylinder was 95 feet in length by 35 feet in diameter. In this cylinder a diving bell was improvised, about 20 feet above the lower end, and from the centre of this extended a smaller tube 10 feet in diameter. Inside the diving bell was placed another cylinder, 27 feet in diameter, divided vertically into 11 compartments, each of which was kept dry by compressed air. In this way the compressed air working space was confined to a ring of compartments, instead of the whole area beneath the dome. The air-
Once the caisson was bedded the substructure proceeded rapidly. The masons set the ashlar granite masonry in the com-
A LOCOMOTIVE GRAVEYARD -
Withdrawn from service by the conversion of the gauge from 7 feet to 4 feet 8½ inches.
Measurements of the Spans
While the subaqueous work was in progress the two huge spans were taken in hand. They are of unusual design, comprising a combination of the tubular and suspension bridge principles. The top member of the truss is an arched elliptical tube, 16¾ feet wide, 12¼ feet deep, by 100 feet in length, carried out in wrought iron. From end to end on each side there are heavy suspension chains. At eleven points, on each side of the tube, are vertical struts, braced by diagonal ties, whereby the chains are connected to the tube. The track floor is a horizontal girder suspended from the truss, the depth of the latter in the centre being 50 feet. When completed each span weighed 1,060 tons.
How the Spans Were Raised
These spans were built on the Devonshire shore, and the method adopted for their transference to the site and placing in position was distinctly ingenious. A dock was excavated under each end of the span, into which pontoons were floated at low tide. On the deck of each pontoon a massive timber staging was built to receive the end of the truss. When the water
rose it lifted the pontoon and the span, until at last the steel was supported entirely on the pontoons. The mass of steel was floated out into the river and warped into position between the central and the shore piers. Five vessels were stationed in the river for this purpose, and by cable and capstan the floating deadweight was brought into place. In this work alone some 500 men were requisitioned under the personal supervision of Brunel. Water was admitted into the pontoons, causing them to sink, when they were drawn clear, leaving the ends of the span resting upon the bases of the piers.
The truss itself was lifted gradually as the masonry work on the piers proceeded. Three hydraulic presses were placed under each end of the truss, and at a given signal the structure was lifted about 3 feet. The masons then built up the pier in the under space, when the steel was lifted once more. By this novel lifting and building alternately the iron work was raised to its designed height. When the first span was completed the second was taken in hand and the cycle of operations was repeated. On this occasion, however. Brunel was unable to direct operations, having been stricken down by illness.
The bridge was completed, and opened by the Prince Consort, after whom it is named, on May 3rd, 1859. Its total length, including the viaduct approaches on each bank, is 2,200 feet, the rails being laid at 110 feet above high water. It carries a single track, Brunel having decided that thereby £100,000 might be saved in first cost. This was a vital consideration in those days, and needless to say was adopted with alacrity. Although the line on either side is double, no serious incon-
THE ROYAL ALBERT BRIDGE AT SALTASH WHICH CARRIES THE RAILWAY ACROSS THE TAMAR
The Cornish Viaducts
Previous to the construction of the Saltash Bridge Brunel had accomplished some remarkably striking feats in carrying the railway through rugged Cornwall. The broken character of the country, and the lack of funds, compelled him to introduce some stiff gradients and sharp curves. Still, the most noticeable features of this line were the timber viaducts, spanning the deep ravines. Some of these structures were of formidable proportions, the Landore Viaduct, for instance, being 1,700 feet in length, comprising 37 openings varying from 40 to 100 feet, while the St. Pinnock Viaduct brought the rail level 103 feet above tihe floor of the valley. The Walkham Viaduct of fifteen spans was 1,100 feet from end to end, and in the highest part 132 feet above the bottom of the rift. Wood was utilised as a constructional material to save expense, and the design comprised timber towers erected on masonry piers, with the deck carried on fan-
In revising and modernising the Cornish line the Great Western Railway replaced the timber structures by masonry and steel. Seeing that over sixty structures had to be replaced in this manner some idea of the magnitude of this modernisation work may be gained. Re-
But possibly the greatest engineering work associated with the Great Western Railway is the link whereby through railway communication is effected between the English and Welsh banks of the River Severn. In 1857 a company was incorporated, under the title of the Bristol and South Wales Union Railway, to run a line from Bristol into the Principality, the interruption of 2½ miles wide offered by the waterway being overcome by a steam ferry. In 1868 the Great Western acquired this railway, but the water-
The designs called for a double track bore 7,664 yards in length, with approaches rising 1 in 90 on the English and 1 in 100 on the Welsh shores respectively, between New Passage and Portskewet, although the river is only some 2¼ miles wide at this point. It was necessary to dip down somewhat deeply in order to clear the hollows in the bed of the river, one such depression, known as the “Shoots”, half-
Trouble with water was anticipated, owing to the geological formation comprising shale, sandstones and marl, but even the worst anticipations were exceeded eventually.
The Great Western Railway undertook the task and prosecuted it sedulously for six and a half years. On October 16th, 1871, there was a terrific water-
LOOKING THROUGH THE ROYAL ALBERT BRIDGE, SALTASH
The total length, including approaches, is 2,200 feet, and the single track is 110 feet above high water.
All efforts to cope with the inundation with the existing pumping plant proved fruitless, so that work was brought to a standstill. The expert assistance of Sir John Hawkshaw, who had been consulting engineer up to this point, was called in, and he instantly recommended drastic expedients which were beyond the railway company. Thereupon the latter decided to withdraw from the undertaking, to place the whole responsibility upon Sir John Hawkshaw, and to let the work to contract. Mr. T. A. Walker, the well-
Diver Lambert’s Success
Heavy oak shields were built and lowered into the water to be attached to the sides of the driftways, fitted with massive doors, so as to divide the bore into sections. One doorway was placed beneath the river itself, 330 yards from the shaft, and time after time divers descended to close this portal, but in vain. They were forced to retreat on every occasion. Finally, Diver Lambert, one of the most expert of submarine toilers, volunteered to attempt the task, notwithstanding its dangerous character. He donned a Fleuss dress, wherein the diver carries his air supply with him, thereby dispensing with the long trail of air-
When the water-
THE FLOODING OF THE SEVERN TUNNEL.
Owing to the water breaking into and flooding the workings, boring was brought to a standstill until Diver Lambert volunteered to penetrate the heading to close a heavy door isolating the affected section, in which daring task he was successful.
Tunnel Flooded for Three Years
Meanwhile Sir John Hawkshaw, having been appointed chief engineer, had revised the plans. He lowered the tunnel by 15 feet, thereby increasing the depth between the roof and the river bed to 15 feet. No attempt to remove the water held back by the door was made until 3½ years later, during which time a new pumping shaft was sunk. When the water was cleared out it was found that a part of the roof had fallen in behind the door, leaving a cavity 40 feet in height. The pumps were kept going removing the 6,000 gallons of water which poured in every minute, and the debris was cleared away.
A Second Flooding
As the level of the tunnel had been lowered, a new driftway was driven below the old one, so that what was originally the bottom heading now became the upper one. The water was kept down completely until the borers had penetrated to a point about 100 yards beyond the door which Lambert had closed, where the first water-
The new driftway, like the old, had been fitted with doors as a precaution, but whereas the men closed the upper one in their rush, the lower door could not be pushed against the water pressure. Before anything could be done it was essential that this door should be closed. It demanded a diver, and he had a crawl of 150 yards to the spot from the bottom of the shaft. Again Diver Lambert came to the rescue. In an ordinary diving suit, and with the assistance of two comrades, one standing at the bottom of the shaft and another about 75 yards along the tunnel to manipulate his air pipe, he succeeded in reaching and closing the door.
When this was accomplished the level of the water was reduced speedily, and as soon as the tunnel could be entered a massive wall, 15 feet in thickness, was thrown up across the bore 88 yards from the shaft. This was equipped with a heavy iron door, together with sluices, and directly the pumping machinery had been increased, so as to lift 27,000 gallons of water per minute, the flooded area was cleared. It was found in this instance that the incoming water had torn a huge hole in the floor of the driftway. This was filled with clay puddle, and covered with a mound of the same material in bags. Subsequently this mound was levelled off and covered with concrete. A little farther on another fall of the roof was found. This was a fortunate discovery, as otherwise another inundation would have resulted. This disaster was avoided by timbering up the roof with all speed, and finally bricking it in cement when the tunnel lining advanced.
THE “QUEEN BOADICEA”, OF THE 4-
The tunnel is of semicircular arch section, with a diameter of 20 fret inside the lining, and a headway of 20 feet in the centre. A permanent pumping plant was installed on the Welsh side, together with a ventilating system. The pumps are capable of meeting any demand that is likely to be made upon them by the spring which caused so much trouble in the early days, so that now no water finds its way into the bore, the spring emptying into and being removed from the shaft provided for the purpose.
The tunnel was opened for goods traffic in September, 1880, after some 13½ years’ labour. When work was in full swing over 4,000 men found employment. Although longer tunnels have been bored in other parts of the world, few have offered such perplexing and peculiar difficulties as were encountered under the Severn. Passengers first travelled by railway under the waterway on December 1st, 1880, and to-
ERECTING ONE OF THE MAIN SPANS OF THE ROYAL ALBERT BRIDGE, SALTASH.
The mass of wrought iron, 460 feet in length, weighed 1,060 tons. It was floated out to the site on pontoons and lifted 3 feet at a time by jacks as the masonry piers were built up to the designed level.
The last great enterprise which the Great Western Railway took in hand was the construction of Fishguard Harbour, to-
Milford, which offered an excellent natural harbour. When the engineers came along half-
While the original London and Bristol line has been brought to a high state of efficiency, and enables passengers to cover the 118 miles between the two points in 120 minutes, a new route for western points has been laid parallel to the parent road, though some miles to the south, between Reading and Taunton. In this way the old line via Bristol has been relieved of a considerable volume of traffic. A fast through line has been provided also between London and Birmingham, as well as other important points in the western midlands.
[From Parts 5-