MECHANICAL AND USEFUL ARTS. 73 



sphere in such a tunnel after the passing of heavy trains becomes 

 so charged with steam and sulphurous vapour, that the plate- 

 layers cannot work for any length of time continuously, and hence 

 there is a difficulty in properly lifting and packing the permanent 

 way. Again, the condensation of the steam upon the rails in 

 single-line tunnels practically increases the expense of working. 

 From the commencement of the Lindal tunnel works in June, 1855, 

 to their completion in November, 1856, nearly seven thousand five 

 hunched passenger trains, conveying one hundred and twelve thou- 

 sand passengers, and two thousand one hundred goods trains, carry- 

 ing two hundred and five thousand tons of minerals, &c, exclusive 

 of light engines, passed through the tunnel, without the slightest 

 casualty to either description of train, or any accident, even of the 

 most trivial character to any individual. A special code of rules 

 was arranged for working the traffic, and for watching and signalling 

 every train. The stations at each end of the tunnel were in tele- 

 graphic communication, and there were semaphore signals at each 

 entrance, connected by an endless wire. The wire was fastened to 

 wheels at various points, having cranks outside the trough in 

 which it was enclosed. A signalman, whose duty it was to remain 

 in the tunnel, could, by means of a portable lever, lower both 

 semaphore signals simultaneously. As a precautionary measure, 

 the signalman sounded a large gong on being informed by the tele- 

 graph that a train was approaching ; and it was not until he had 

 satisfied himself that no impediment existed to the passage of the 

 train, that he lowered the signals, and thus sanctioned the engine 

 drivers to proceed. 



PREVENTABLE RISK IN FAST RAILWAY TRAVELLING. 



In a Report to the Board of Trade, on the accident at Hatfield in 

 the month of April, 1860, when a Great Northern train after passing 

 over a rail that had been turned got off the line, and Mr. Pym, a 

 passenger, lost his life, Colonel Yolland states that the whole weight 

 of the train was about 100 tons, and the total weight on the 

 wheels to which break blocks could he applied was but about 26 

 tons. Now a train at Hatfield, travelling down an incline of 1 in 

 200 at the rate of 60 miles an hour (a frequent rate of that train 

 at that point), could not have been stopped by these breaks in less 

 than three-quarters of a mile. Colonel Yolland says this is a very 

 unsatisfactory condition attending fast railway travelling, and that 

 such quick trains ought to be furnished with an amount of break 

 power which will enable them to be stopped in a third of that dis- 

 tance, and that this can be done by means of continuous breaks, 

 which augment the retarding power three or four fold. Two years 

 ago the Board of Trade sent to all railway companies a report of 

 the successful working of such breaks on the East Lancashire Bail- 

 way, where a train of 90 tons, supplied with 80 per cent, of break 

 power, travelling at the rate of 53 miles an hour down an incline 

 of 1 in 120, was stopped after running 235 yards. The carriage 

 in which Mr. Pym rode was not thrown over on its side until it 

 was 408 yards from the spot where the accident occurred. 



