Part 12 (2/2)

Unlike the bogs or swamps of Cambridge and Lincolns.h.i.+re, which consist princ.i.p.ally of soft mud or silt, this bog is a vast ma.s.s of spongy vegetable pulp, the result of the growth and decay of ages. The spagni, or bog-mosses, cover the entire area; one year's growth rising over another,-the older growths not entirely decaying, but remaining partially preserved by the antiseptic properties peculiar to peat. Hence the remarkable fact that, although a semifluid ma.s.s, the surface of Chat Moss rises above the level of the surrounding country. Like a turtle's back, it declines from the summit in every direction, having from thirty to forty feet gradual slope to the solid land on all sides. From the remains of trees, chiefly alder and birch, which have been dug out of it, and which must have previously flourished upon the surface of soil now deeply submerged, it is probable that the sand and clay base on which the bog rests is saucer-shaped, and so retains the entire ma.s.s in position.

In rainy weather, such is its capacity for water that it sensibly swells, and rises in those parts where the moss is the deepest. This occurs through the capillary attraction of the fibres of the submerged moss, which is from 20 to 30 feet in depth, whilst the growing plants effectually check evaporation from the surface. This peculiar character of the Moss has presented an insuperable difficulty in the way of reclaiming it by any system of extensive drainage-such as by sinking shafts, and pumping up the water by steam power, as has been proposed.

Supposing a shaft of 30 feet deep to be sunk, it has been calculated that this would only be effectual for draining a circle of about 100 yards, the water running down an incline of about 5 to 1; for it was found in the course of draining the bog, that a ditch 3 feet deep only served to drain a s.p.a.ce of less than 5 yards on each side, and two ditches of this depth, 10 yards apart, left a portion of the Moss between them scarcely affected by the drains.

The three resident engineers selected by Mr. Stephenson to superintend the construction of the line, were Joseph Locke, William Allcard, and John Dixon. The last was appointed to that portion which lay across the Moss, neither of the other two envying his lot. On Mr. Dixon's arrival, about July, 1826, Mr. Locke proceeded to show him over the length he was to take charge of, and to instal him in office. When they reached Chat Moss, Mr. Dixon found that the line had already been staked out and the levels taken in detail by the aid of planks laid upon the bog. The cutting of the drains along each side of the proposed road had also been commenced; but the soft pulpy stuff had up to this time flowed into the drains and filled them up as fast as they were cut. Proceeding across the Moss, on the first day's inspection, the new resident, when about halfway over, slipped off the plank on which he walked, and sank to his knees in the bog. Struggling only sent him the deeper, and he might have disappeared altogether, but for the workmen, who hastened to his a.s.sistance upon planks, and rescued him from his perilous position. Much disheartened, he desired to return, and even thought of giving up the job; but Mr. Locke a.s.sured him that the worst part was now past; so the new resident plucked up heart again, and both floundered on until they reached the further edge of the Moss, wet and plastered over with bog-sludge. Mr. Dixon's companions endeavoured to comfort him by the a.s.surance that he might avoid similar perils, by walking upon ”pattens,”

or boards fastened to the soles of his feet, as they had done when taking the levels, and as the workmen did when engaged in making drains in the softest parts of the Moss. The resident engineer was sorely puzzled in the outset by the problem of constructing a road for heavy locomotives, with trains of pa.s.sengers and goods, upon a bog which he had found incapable of supporting his own weight!

Mr. Stephenson's idea was, that such a road might be made to _float_ upon the bog, simply by means of a sufficient extension of the bearing surface. As a s.h.i.+p, or a raft, capable of sustaining heavy loads floated in water, so in his opinion, might a light road be floated upon a bog, which was of considerably greater consistency than water. Long before the railway was thought of, Mr. Roscoe had adopted the remarkable expedient of fitting his plough-horses with flat wooden soles or pattens, to enable them to walk upon the Moss land which he had brought into cultivation. These pattens were fitted on by means of a screw apparatus, which met in front of the foot and was easily fastened. The mode by which these pattens served to sustain the horse is capable of easy explanation, and it will be observed that the _rationale_ likewise explains the floating of a railway train. The foot of an ordinary farm-horse presents a base of about five inches diameter, but if this base be enlarged to seven inches-the circles being to each other as the squares of the diameters-it will be found that, by this slight enlargement of the base, a circle of nearly double the area has been secured; and consequently the pressure of the foot upon every unit of ground upon which the horse stands has been reduced one half. In fact, this contrivance has an effect tantamount to setting the horse upon eight feet instead of four.

Apply the same reasoning to the ponderous locomotive, and it will be found, that even such a machine may be made to stand upon a bog, by means of a similar extension of the bearing surface. Suppose the engine to be 20 feet long and 5 feet wide, thus covering a surface of 100 square feet, and, provided the bearing has been extended by means of cross sleepers supported on a matting of heath and branches of trees covered with a few inches of gravel, the pressure of an engine of 20 tons will be only equal to about 3 pounds per inch over the whole surface on which it stands.

Such was George Stephenson's idea in contriving his floating road-something like an elongated raft across the Moss; and we shall see that he steadily kept it in view in carrying the work into execution.

The first thing done was to form a footpath of ling or heather along the proposed road, on which a man might walk without risk of sinking. A single line of temporary railway was then laid down, formed of ordinary cross-bars about 3 feet long and an inch square, with holes punched through them at the ends and nailed down to temporary sleepers. Along this way ran the waggons in which were conveyed the materials requisite to form the permanent road. These waggons carried about a ton each, and they were propelled by boys running behind them along the narrow iron rails. The boys became so expert that they would run the 4 miles across at the rate of 7 or 8 miles an hour without missing a step; if they had done so, they would have sunk in many places up to their middle. A comparatively slight extension of the bearing surface being found sufficient to enable the bog to bear this temporary line, the circ.u.mstance was a source of increased confidence and hope to our engineer in proceeding with the formation of the permanent roadway alongside.

The digging of drains had been proceeding for some time along each side of the intended line; but they filled up almost as soon as dug, the sides flowing in, and the bottom rising up. It was only in some of the drier parts of the bog that a depth of three or four feet could be reached.

The surface-ground between the drains, containing the intertwined roots of heather and long gra.s.s, was left untouched, and upon this was spread branches of trees and hedge-cuttings. In the softest places, rude gates or hurdles, some 8 or 9 feet long by 4 feet wide, interwoven with heather, were laid in double thicknesses, their ends overlapping each other; and upon this floating bed was spread a thin layer of gravel, on which the sleepers, chairs, and rails were laid in the usual manner.

Such was the mode in which the road was formed upon the Moss.

It was found, however, after the permanent way had been thus laid, that there was a tendency to sinking at those parts where the bog was softest.

In ordinary cases, where a bank subsides, the sleepers are packed up with ballast or gravel; but in this case the ballast was dug away and removed in order to lighten the road, and the sleepers were packed instead with cakes of dry turf or bundles of heath. By these expedients the subsided parts were again floated up to the level, and an approach was made towards a satisfactory road. But the most formidable difficulties were encountered at the centre and towards the edges of the Moss; and it required no small degree of ingenuity and perseverance on the part of the engineer successfully to overcome them.

The Moss, as already observed, was highest in the centre, and it there presented a sort of hunchback with a rising and falling gradient. At that point it was found necessary to cut deeper drains in order to consolidate the ground between them on which the road was to be formed.

But, as at other places, the deeper the cutting the more rapid was the flow of fluid bog into the drain, the bottom rising up almost as fast as it was removed. To meet this emergency, numbers of empty tar-barrels were brought from Liverpool; and as soon as a few yards of drain were dug, the barrels were laid down end to end, firmly fixed to each other by strong slabs laid over the joints, and nailed. They were then covered over with clay, and thus formed an underground sewer of wood instead of bricks. This expedient was found to answer the purpose intended, and the road across the centre of the Moss having been so prepared, it was then laid with the permanent materials.

The greatest difficulty was, however, experienced in forming an embankment upon the edge of the bog at the Manchester end. Moss as dry as it could be cut, was brought up in small waggons, by men and boys, and emptied so as to form an embankment; but the bank had scarcely been raised three or four feet in height, when the stuff broke through the heathery surface of the bog and sank out of sight. More moss was brought up and emptied with no better result; and for weeks the filling was continued without any visible embankment having been made. It was the duty of the resident engineer to proceed to Liverpool every fortnight to obtain the wages for the workmen employed under him; and on these occasions he was required to colour up, on a section drawn to a working scale suspended against the wall of the directors' room, the amount of excavation and embankment from time to time executed. But on many of these occasions, Mr. Dixon had no progress whatever to show for the money expended on the Chat Moss embankment. Sometimes, indeed, the visible work done was _less_ than it had appeared a fortnight or a month before!

The directors now became seriously alarmed, and feared that the evil prognostications of the eminent engineers were about to be fulfilled.

The resident engineer was even called upon to supply an estimate of the cost of forming an embankment of solid stuff throughout, as also of the cost of piling the roadway, and in effect constructing a four mile viaduct of timber across the Moss, from twenty to thirty feet high from the foundation. The expense appalled the directors, and the question arose, whether the work was to be proceeded with or _abandoned_!

Mr. Stephenson afterwards described the alarming position of affairs at a public dinner at Birmingham (23rd December, 1837), on the occasion of a piece of plate being presented to his son, upon the completion of the London and Birmingham Railway. He related the anecdote, he said, for the purpose of impressing upon the minds of those who heard him the necessity of perseverance.

”After working for weeks and weeks,” said he, ”in filling in materials to form the road, there did not yet appear to be the least sign of our being able to raise the solid embankment one single inch; in short we went on filling in without the slightest apparent effect. Even my a.s.sistants began to feel uneasy, and to doubt of the success of the scheme. The directors, too, spoke of it as a hopeless task: and at length they became seriously alarmed, so much so, indeed, that a board meeting was held on Chat Moss to decide whether I should proceed any further. They had previously taken the opinion of other engineers, who reported unfavourably. There was no help for it, however, but to go on. An immense outlay had been incurred; and great loss would have been occasioned had the scheme been then abandoned, and the line taken by another route. So the directors were _compelled_ to allow me to go on with my plans, of the ultimate success of which I myself never for one moment doubted.”

During the progress of this part of the works, the Worsley and Trafford men, who lived near the Moss, and plumed themselves upon their practical knowledge of bog-work, declared the completion of the road to be utterly impracticable. ”If you knew as much about Chat Moss as we do,” they said, ”you would never have entered on so rash an undertaking; and depend upon it, all you have done and are doing will prove abortive. You must give up the idea of a floating railway, and either fill the Moss hard from the bottom, or deviate so as to avoid it altogether.” Such were the conclusions of science and experience.

In the midst of all these alarms and prophecies of failure, Stephenson never lost heart, but held to his purpose. His motto was ”Persevere!”

”You must go on filling in,” he said; ”there is no other help for it.

The stuff emptied in is doing its work out of sight, and if you will but have patience, it will soon begin to show.” And so the filling in went on; several hundreds of men and boys were employed to skin the Moss all round for many thousand yards, by means of sharp spades, called by the turf cutters ”tommy-spades;” and the dried cakes of turf were afterwards used to form the embankment, until at length as the stuff sank and rested upon the bottom, the bank gradually rose above the surface, and slowly advanced onwards, declining in height and consequently in weight, until it became joined to the floating road already laid upon the Moss. In the course of forming the embankment, the pressure of the bog turf tipped out of the waggons caused a copious stream of bog-water to flow from the end of it, in colour resembling Barclay's double stout; and when completed, the bank looked like a long ridge of tightly pressed tobacco-leaf. The compression of the turf may be imagined from the fact that 670,000 cubic yards of raw moss formed only 277,000 cubic yards of embankment at the completion of the work.

At the western, or Liverpool end of the Chat Moss, there was a like embankment; but, as the ground there was solid, little difficulty was experienced in forming it, beyond the loss of substance caused by the oozing out of the water held by the moss-earth.

At another part of the Liverpool and Manchester line, Parr Moss was crossed by an embankment about 1 mile in extent. In the immediate neighbourhood was found a large excess of cutting, which it would have been necessary to ”put out in spoil-banks” (according to the technical phrase); but the surplus clay, stone, and shale, were tipped, waggon after waggon, into Parr Moss, until a solid but concealed embankment, from fifteen to twenty-five feet high, was formed, although to the eye it appears to be laid upon the level of the adjoining surface, as at Chat Moss.

The road across Chat Moss was finished by the 1st January, 1830, when the first experimental train of pa.s.sengers pa.s.sed over it, drawn by the ”Rocket;” and it turned out that, instead of being the most expensive part of the line, it was about the cheapest. The total cost of forming the line over the Moss was 28,000, whereas Mr. Giles's estimate was 270,000! It also proved to be one of the best portions of the railway.

Being a floating road, it was smooth and easy to run upon, just as Dr.

Arnott's water-bed is soft and easy to lie upon-the pressure being equal at all points. There was, and still is, a sort of springiness in the road over the Moss, such as is felt in pa.s.sing along a suspended bridge; and those who looked along the line as a train pa.s.sed over it, said they could observe a waviness, such as precedes and follows a skater upon ice.

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