The appointment of principal engineer to the railway was taken into consideration at the first meeting of the directors held at Liverpool subsequent to the passing of the Act. The magnitude of the proposed works, and the vast consequences involved in their experiment, were deeply impressed upon their minds; and they resolved to secure the services of a resident engineer of proved experience and ability. Their attention was naturally directed to Mr. Stephenson; at the same time they desired to have the benefit of the Messrs. Rennie’s professional assistance in superintending the works. Mr. George Rennie had an interview with the Board on the subject, at which he proposed to undertake the chief superintendence, making six visits in each year, and stipulating that he should have the appointment of the resident engineer. But the responsibility attaching to the direction in the matter of the efficient carrying on of the works, would not admit of their being influenced by ordinary punctilios on the occasion; and they accordingly declined this proposal, and proceeded to appoint Mr. Stephenson their principal engineer at a salary of £1000 per annum.
He at once removed his residence to Liverpool, and made arrangements to commence the works. He began with the “impossible thing”—to do that which the most distinguished engineers of the day had declared that “no man in his senses would undertake to do”—namely, to make the road over Chat Moss! It was indeed a most formidable undertaking; and the project of carrying a railway along, under, or over such a material as that of which it consisted,
would certainly never have occurred to an ordinary mind. Michael Drayton supposed the Moss to have had its origin at the Deluge. Nothing more impassable could have been imagined than that dreary waste; and Mr. Giles only spoke the popular feeling of the day when he declared that no carriage could stand on it “short of the bottom.” In this bog, singular to say, Mr. Roscoe, the accomplished historian of the Medicis, buried his fortune in the hopeless attempt to cultivate a portion of it which he had bought.
Chat Moss is an immense peat bog of about twelve square miles in extent. Unlike the bogs or swamps of Cambridge and Lincolnshire, which consist principally of soft mud or silt, this bog is a vast mass 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 mass, 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 mass 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 space 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 assistance 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 assured 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 assurance 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 passengers 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 ship, 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.