페이지 이미지

the family moved from London to the north there was no possibility of reaching Holkar within a reasonable time except across the sands, and preparations used to be made a fortnight or three weeks before the journey commenced, several trusty men being commissioned to meet the coach at Lancaster and conduct it safely on the way.

Down to the past summer, indeed, a stagecoach plied across the sands from Lancaster to Ulverston—now superseded by the rail, and many are the hairbreadth escapes that occurred in the crossing. Nor did the travellers always escape the perils of the journey. The registers of the parish of Cartmell show that not fewer than a hundred persons have been buried in its churchyard who were drowned in attempting to pass over the sands. This is independent of the similar burials in other churchyards in adjacent parishes on both sides of the bay. Only in the course of last spring a party of ten or twelve young men and women, proceeding to the hiring market at Lancaster, were overtaken by the advancing tide, when every one of them perished. The principal danger arose from the treacherous nature of the sands, and their constant shifting during the freshes which occurred in the rivers flowing into the head of the bay.

As early as the year 1837 Mr. George Stephenson recommended the construction of a railway from Poulton, near Lancaster, to Humphrey Head, on the opposite coast, as part of a west coast line to Scotland. He proposed to carry the road across the sands in a segment of a circle of five miles radius. His design was to drive in piles for the whole length, and form a solid fence of stone blocks on the land side of the piles, for the purpose of retaining the sand and silt brought down by the rivers from the interior. It was calculated that the value of the forty thousand acres of rich alluvial land thus reclaimed from the bay would have more than covered the cost of forming the embankment. But the scheme was not prosecuted ; and though afterwards taken up by Mr. Hague, and supported by Mr. Rastrick, it slept for many years, until recently a line has been carried across Morecambe Bay, though in a greatly modified form, by the Ulverstone and Lancaster Railway Company. Mr. Brogden, a wealthy railway contractor, was the soul of the revived undertaking; and, had he been better supported, it was his intention to have taken the line straight across the bay somewhat after Mr. Stephenson's plan. It was, however, eventually determined to reduce the extent of the sea works, and to carry the railway nearer to the land, across the estuaries of the rivers Kent and Leven.

The people of the neighbourhood regarded the scheme as one of the wildest that had ever been heard of. The idea


of forming a solid road across about eight miles of sands, which from time immemorial had been to them the type of everything that was shifting and unstable, appeared to be even more wild and absurd than that of the foolish man in the parable, who built his house upon a similarly treacherous foundation. The prophecies that were ventured upon the subject were only paralleled by those which predicted that a road could never be made across Cbat Moss. Besides the washing of the railway embankment on the land side by the rivers flowing into the sea, there was the washing of the sea-waves on the other side to be provided against. The work during its progress was a daily encounter with difficulties, occurring at every flux and reflux of the tide; and when to the flow of the water was added the force of a south-westerly storm, the temporary havoc made in the embankments was calculated greatly to discourage the projectors of the undertaking.

The principal obstacles were encountered in crossing the estuary of the Leven. In making the borings nothing but sand was found to a depth of thirty feet. In one case the boring was carried seventy feet down, and still there was nothing but sand. It was necessary, in the first place, to confine the channel of the river to a fixed bed, which was accomplished by means of weirs formed of quarry rid.' No small difficulty was experienced in

' getting these weirs run out in the right line, in consequence of the eddies produced by the tide at its flux and reflux washing deep holes in the sand on either side. To prevent these eddies undermining the foundations of the work, toes of loose stones were run out, with lateral wings thrown off from their ends, which had the effect of keeping the holes made by the tide out of the line of the embankment or main weir, which was then carried steadily forward. When the current had at length been fixed, a viaduct of fifty spans of thirty feet each was thrown over the channel, and in the viaduct was placed a drawbridge to permit the passage of sailing vessels. To protect the foundations of the piers of this viaduct, as well as the railway embankment, weirs were also formed parallel with the current of the stream, which had the further effect of retaining the silt inland, and thus enabling large tracts of valuable land to be reclaimed.

The crossing of the Kent estuary was accomplished in a similar manner, by means of weirs and embankments, over ground where the borings showed the sand to be of the depth of from fourteen to twenty-one feet; a viaduct of similar dimensions to that across the Leven, providing for the outfall of the river. The land reclaimed behind the embankments at this point



is now under cultivation, where only a short time since fishingboats were accustomed to ply their trade. The chief difficulty which the engineer had to encounter was in finding a solid foundation amidst the shifting sands for the piers of the extensive viaducts across the mouths of the two rivers. The details of the plan he adopted for sinking iron piles would be too technical to be entered upon here. It is sufficient to say that the entire work has been satisfactorily achieved, and must be regarded as another triumph of English engineering over that element which usually tests their highest skill.

But greater obstacles than all that we have yet described have been encountered in the underground work of tunnelling. At a public dinner at Norwich, during the railway mania, it was facetiously suggested that directors always liked perfect flats to work upon.' But few English counties are so flat as the Eastern, and there are not many lines of any extent in this country where it has been found practicable to dispense altogether with tunnelling. The undulating nature of the soil renders it necessary to bore where an open road cannot be cut, where a detour to avoid the high ground would be too circuitous, or where an inclined road over the high ground would be too steep to be economically worked by the locomotive. The tunnel usually occurs where a line crosses from the head of one valley into the head of another, as from the Yorkshire into the Lancashire valleys, under the rocky mountain-ridge known as the backbone

6 of England.' No less than three tunnels have been constructed under this high ground : at Woodhead, on the Manchester and Sheffield Railway; at Stanedge (formerly a canal tunnel), on the Huddersfield and Manchester ; and at Littleborough, on the Manchester and Lecds line.

The usual mode of executing a tunnel is as follows. A careful preliminary examination is made of the geological strata, so far as these can be discerned from the external features of the country; and levels or soundings are taken, from which a profile of the surface of the ground to be passed under may be formed. To test the character of the underground strata, before letting the works to contractors, vertical borings are made through the site of the proposed tunnel, or trial shafts are sunk with the same object. No matter how thorough this preliminary examination may be, the nature of the strata throughout cannot be ascertained with perfect accuracy; and it may so happen, as in the case of the Kilsby Tunnel, that the most dangerous part of the ground may not be disclosed. In some cases, where the tunnel is of no great extent, a driftway is dug through its whole length. But this cannot be done when the work is extensive; and then the tunnel is commenced at various points, by means of vertical working shafts sunk from the surface down to the base of the tunnel. When this is reached, excavating, followed by building in of the brick or stone work of the tunnel, proceeds abreast each way, the excavated stuff being drawn up the shaft by means of a borse gin, or by steam-power. The tunnel is usually worked in lengths of about twenty feet, and arched with brick or stone froin eighteen inches to two feet in thickness. By this method a large number of short tunnels are formed, which in the course of the work are ultimately united into one, and a vast body of men can be employed without confusion at the same time. The precision with which the survey is taken, and the line of the tunnel struck from the shaft heads, is such that the various lengths, when completed, often meet each other to an inchbreadth, or less. Mistakes have, however, happened, when the lines have been struck by inexperienced surveyors, as in the case of a tunnel on a northern line, when the workmen in different lengths found on one occasion, from the noise made by the underground blasting, that they were working past each other. The error, which was repaired at considerable cost, had been occasioned by the curve at the bottom of one of the shafts having been accidentally laid out in the wrong direction.


One of the most delicate peices of tunnel surveying and underground building was executed at Glasgow, on the short branch railway connecting the Garnkirk Railway with the Buchanan Street Terminus of the Caledonian Railway. It was found necessary to pass, by means of a tunnel 400 feet in length, under the Monkland Canal, and over the Tunnel of the Edinburgh and Glasgow Railway. There was barely space for the purpose, the floor of the one tunnel being only ten feet above the roof of the other. But to prevent the upper erection from resting heavily upon the lower one, arches of seventy feet span were constructed, on which the walls of the upper tunnel were supported, so that the entire weight was borne by the solid ground on either side. The arch of the tunnel was elliptical, and formed of bricks composed of a mixture of common and fire clay; and in order to give additional strength, an inverted arch of the same materials was turned below the rails. All this work was performed underground; and, during its progress, the difficulty of execution was increased by the breaking in of the waters from the canal above. But this too was successfully mastered, and the two tunnels now stand secure tier above tier, under the bed of the Monkland Canal. A similarly delicate piece of work was executed on the North Midland Railway at Bullbridge, in Derbyshire, where the line at the same point passed over a bridge which here spanned the river Amber, and under the bed of the Cromford Canal. Water, bridge, railway, and canal, were thus piled one above the other four stories high. Such another curious complication does not probably exist. In order to prevent the possibility of the waters of the canal breaking in upon the works of the railroad, the engineer, (Mr. George Stephenson) had an iron tank made 150 feet long, of the width of the canal, and exactly fitting the bottom. It was brought to the spot in three pieces, which were welded firmly together. The trough was floated into its place and sunk, and the railway works underneath were then proceeded with in safety.


The difficulties we have been enumerating have, nevertheless, been surpassed by those which have occurred in forming tunnels of great magnitude, such as the Box Tunnel on the Great Western Railway, the Woodhead Tunnel on the Sheffield and Manchester Railway, and the Kilsby Tunnel on the London and North Western Railway. In excavating the Box Tunnel, great quantities of water were met with. At one place heavy rains occasioned an immense influx, which drowned out' the workmen, and not only filled the tunnel, but rose to a height of 56 feet in the shaft. The engineers had to go on pumping for months, though as much as 32,000 hogsheads were thrown out in the course of the twenty-four hours.

Any one who casts his eye upon a map of the county of Chester will observe a narrow tongue of land at its easternmost corner, extending towards Yorkshire, between the counties of Derby and Lancaster. At this approximation of the four counties the Woodhead tunnel penetrates the mountain ridge for a length of about three miles under a dreary, barren moor, undisturbed save by the sportsman's gun. The usual shafts were sunk over the line of the tunnel down towards its base, The

average depth of the shafts was about 600 feet; but it was long indeed before the workmen could reach the bottom level. The sinking, blasting, and winding went on so slowly that the tunnel was six years in progress. This was caused partly by the hardness of the material, and partly by the immense quantity of water which flowed into the shafts. The pumping continued for five years, during which time the engines threw up not less than eight million tons of water. At two of the shafts, where continuous pumping went on, not an inch was gained during nine months. In another it took eleven months to sink fourteen yards, the workmen coffering out the water as they descended with ashlar stonework bedded in one-inch boards. But the enemy was never fairly mastered until the under-drift was blasted through the line of the tunnel, whereby the upper springs were tapped, and


« 이전계속 »