IT might be thought that the last word had already been said on the subject of the construction of tunnels on the well-tried English system. As, however, the circumstances are in no two cases precisely alike, some details of the construction of a tunnel recently carried out in this way may be of interest to engineers. The opening of new collieries, and the increased output of old ones, together with a general expansion of passenger-and goodstraffic, having resulted in considerable congestion of

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... traffic on certain parts of the Midland Railway Company's system, notably in Derbyshire on the Erewash Valley line between Clay Cross and Trent, the widening of this line was decided on some years ago, and has been gradually carried out, partly by contract and partly by the Company's own staff. The most formidable obstacle to the work was the range of hills on which the town of Alfreton stands, about 10 miles south of Chesterfield. These hills were already pierced by a tunnel 840 yards in length, and it was decided to construct a new tunnel of the same length as the old one, and 90 feet west of it, the old tunnel to be used in future exclusively for goods-traffic. The strata traversed belong to the upper carboniferous period, being chiefly grey sandstone rock, shale and fireclay, with thin seams of coal, dipping about 1 in 40 from south-west to north-east (Fig. l ) . The seams vary in thickness between 1 foot and 2 feet, and the coal, being of fairly good quality, was used by the contractors for the winding-engines and for fires to light the spoil-tips at night. As the tunnel is approached from the north through a cutting of 160,000 cubic yards, and from the south through one of 130,000 cubic yards, it was found impracticable to do any of the tunnelling from the ends. Five shafts were therefore sunk on the centreline, and from these the whole of the work was done. Of the five Downloaded by [ University of Liverpool] on [17/09/16].