Before entering upon a description of the constructive details of this, the longest railway tunnel in the world, it may be well to give a general idea of the undertaking. Many schemes for the connection of Italy and Switzerland by a railway near the Simplon Road Pass have been devised, including one involving no great length of underground work, the line mounting by steep gradients and sharp curves. The present scheme, put forward in 1881 by the Jura-Simplon Ry. Co., consists broadly of piercing the Alps between Brigue, the present railway terminus in the Rhone Valley, and Iselle, in the gorge of the Diveria, on the Italian side, from which village the railway will descend to the existing southern terminus at Domo d’Ossola, a distance of about 11 miles. [8] Abstract from a paper read before the Institution of Civil Engineers by Charles B. Fox, Jan. 26, 1900. In conjunction with this scheme a second tunnel is proposed, to pierce the Bernese Alps under the Lötschen Pass from Mittholz to a point near Turtman in the Rhone Valley; and thus, instead of the long détour by Lausanne and the Lake of Geneva, there will be an almost direct line from Berne to Milan _via_ Thun, Brigue, and Domo d’Ossola. Starting from Brigue, the new line, running gently up the valley for 1¹⁄₄ miles, will, on account of the proximity of the Rhone, which has already been slightly diverted, enter the tunnels on a curve to the right of 1050 ft. radius. At a distance of 153 yards from the entrance, the straight portion of the tunnel commences, and extends for 12 miles. The line then curves to the left with a radius of 1311 ft. before emerging on the left bank of the Diveria. Commencing at the northern entrance, a gradient of 1 in 500 (the minimum for efficient drainage) rises for a length of 5¹⁄₂ miles to a level length of 550 yards in the center, and then a gradient of 1 in 143 descends to the Italian side. On the way to Domo d’Ossola one helical tunnel will be necessary, as has been carried out on the St. Gothard. There will be eventually two parallel tunnels having their centers 56 ft. apart, each carrying one line of way; but at the present time only one heading, that known as No. 1, is being excavated to full size, No. 2 being left, masonry lined where necessary, for future developments. By means of cross headings every 220 yds. the problems of transport and ventilation are greatly facilitated, as will be seen later. As both entrances are on curves, a small “gallery of direction” is necessary, to allow corrections of alinement to be made direct from the two observatories on the axis of the tunnel.