There is a source of danger in connection with travelling through a long tunnel with a bad gradient, that a recent occurrence in the Dove Hole tunnel of the Midland Railway (a tunnel to which special reference is made at page 372), suggests. The accident is so extraordinary in its character that a brief account of it at present will not he out of place. It appears that on the 9th of September last, a ballast train had gone into the tunnel with the intention of the permanent way men supplying it with ballast. Whilst it was at a stand-still and the men were at work, a cattle train, consisting of twenty-seven trucks, and drawn by two powerful goods’ engines, was permitted to enter the tunnel. This cattle train came into collision with the ballast train, when, among other results, one was that the coupling chain which connected the cattle trucks to the engines broke. The trucks thus freed began to descend the incline, which, as already stated, is 1 in 90; their _impetus_ increased each moment, and by the time they emerged from the tunnel, on the wrong line, they were travelling at express speed. Notwithstanding a slight change in the gradient, they went on at that rate for eight miles, continuing always, of course, _on the wrong line_. At that point the trucks came in collision with the engine of an express train from Manchester, which had been standing on its own proper line waiting for the signal it should receive before proceeding onwards. The driver of the express train engine perceiving in a moment what was occurring, reversed his engine, put on full steam, and then jumped off, very unfortunately for himself. But the engine had not sufficient speed upon her to prevent a collision with the cattle trucks. The greater part of these latter were literally crushed to atoms; and, perhaps, fortunately, the cylinders of the express train engine were burst by the collision. This allowed a great escape of steam, and it was ultimately, combined with the presence of mind of a pointsman, the means of the engine not doing more mischief than shaking some and frightening all the passengers travelling in the train belonging to it. Not so five drovers who were in the brake-van of the cattle train: they were killed, and, apparently, their deaths were instantaneous. Such an accident as this is not likely to happen in the tunnel of the Alps; but, suppose a coupling iron broke, and with it the coupling chains, on the French or ascending side, would the brake power attached to the carriages be enough to check their downward speed? At all events, it must not be forgotten that the average gradient on the French side of the tunnel is 1 in 45 (117 feet in the mile), or exactly double as steep as that of the Dove Hole Tunnel, and that the Modane entrance of the tunnel of the Alps is 1,216 feet above St. Michel, consequently there is an average fall per mile during the whole twelve miles of 1 in 101, or at the rate of 50 feet in the mile, and as there