From Samuel Smiles: Lives of the Engineers John Murray 1879
At a part of the North Midland Line, near Ambergate, it was necessary to pass along a hillside in a cutting a few yards deep. As the cutting proceeded, a seam of shale was cut across, lying at an inclination of 6 to 1; and shortly after, the water getting behind the bed of shale, the whole mass of earth along the hill above began to move down across the line of excavation. The accident completely upset the estimates of the contractor, who, instead of 50,000 cubic yards, found that he had about 500,000 to remove; the execution of this part of the railway occupying fifteen months instead of two.
As a curiosity in construction, we may also mention a very delicate piece of work executed on the same railway at Bullbridge in Derbyshire, where the line at the same point passes over a bridge which here spans 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 probably not existing. In order to prevent the possibility of the waters of the canal breaking in upon the works of the railroad, Mr. Stephenson had an iron trough 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 firmly welded together, and the trough was then floated into its place and sunk; the whole operation being completed without in the least interfering with the navigation of the canal. The railway works underneath were then proceeded with and finished.
Photo courtesy Hugh Potter
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