Now and again, however, a train gets out of control, especially when the rails are wet and slippery. To meet this condition of affairs the driver, of course, makes liberal use of sand, but here again the fates are against him, for owing to the sharp curves it is no easy matter to induce the sand falling from the engine’s sand-boxes to drop on the face of, and not between or outside, the rails. When a train does get out of hand on the descent the driver has to trust to luck to gain the bottom of the bank in safety, or to regain control of his charge. Sometimes he succeeds and sometimes he fails. In the latter case derailment generally ensues, with more or less disastrous results. Mr. Dickson had a narrow escape from this danger himself one day. He was carrying out his periodical inspection of the line from his special carriage coupled to a locomotive. In coming down the bank something went wrong, and the train got away. The engineer-in-chief admits that he had an uncomfortably anxious few minutes. He felt the train gather speed, and suffered violent oscillation as the train swung round the bends. Just as he was wondering what would be the end, there was a jump and a crash. The engine had left the track, rolled over, and his car was astride the overturned locomotive. He crawled out of the wreck, badly shaken and bruised, but otherwise little the worse for his adventure, though the unfortunate driver was killed. [Illustration: AN INTERESTING ENGINEERING ACHIEVEMENT This 160-feet bridge span had to be erected and pulled into position over rollers.] [Illustration: BRIDGE OVER THE PARAHYBUNA RIVER, SHOWING HEIGHT OF RIVER IN FLOOD AND FORCE OF WATER SURGING ROUND THE PIERS THE LEOPOLDINA RAILWAY IN BRAZIL] In order to negotiate the third mountain range another solution of the difficulty was adopted. The precipice was so steep that the engineers could not introduce the loops requisite to carry the line continuously from one level to the other. So they had recourse to the switch-back, wherein the line runs down-hill for a short distance to a dead-end. This brings the engine of the descending train to the rear, and by giving the latter a slight push it is sent down another similar switch-back to another dead-end, where the engine is brought once more to the front of the train. In this manner, alternately pulling and pushing, the train gains the bottom or top of the level of the line, according to the direction in which it is travelling. In reality it is a zigzag, similar in character to that which was used for so many years upon the New South Wales railways, as described elsewhere.