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96 THE CIVIL ENGINEER AND ARCHITECT’S JOURNAL. and in the guard’s van, have been in extensive use both in England and on the Continent, they have been found to fail notably in long trains, although it is by no means impossible that means might be found for rendering them more efficient; the difficulty is in dealing with the slack, which in a long train must necessarily be considerable, to allow for the play of the drawsprings, and the general movements of the carriages : there is also a certain liability in the rope to get jammed in special cases. There is however the great advantage of cheapness and simplicity in this arrangement, and on the whole, perhaps, it is attended with fewer disadvantages than any other. Tubes throughout the train, for the conveyance of compressed air, to sound whistles, or to act in any other manner, are sub ject to many inconveniences, in the apparatus for compressing or exhausting the air. Moreover, anything which necessitates very tight joints is to be avoided, for the constant coupling and uncoupling of the carriages must be borne in mind. If the tube were continuous it would entail continual attention whenever the length of the train was varied. It would be remembered throughout in dealing with this subject, that there is an obvious defect in any arrangement which requires thinking of, and looking after all through the day, when its use is not perhaps needed, once in a twelvemonth. The propelling of balls, of pith, or wood, by a blast of air through tubes, is ingenious in conception, but it would require the keeping in order of an air pump in every guard’s van, and it is clear the system would not be at all adapted to the rough usage incidental to a railway traffic such as ours. Simple Speaking Tubes, with whistles for attracting attention, have at first sight a very plausible look about them, but ex periments have proved them to be inapplicable, nor do they seem to have met with greater success in Erance, for the French commissioners, before spoken of, remarks,—•“ Les Nos. 17, etc., croient h 1’efficacitd de tuyaux acoustiqucs, communi quant sur toute la longuer du train. Il est facile de ddmontrer, que ce systeme de communication, serait au contraire entice ment inefficace.” Torsion shafts, or rods, which can be made to gear with each other and so transmit some motion along the train, to sound a signal in the guard’s van, or on the engine, are open to the objection that they could not be applied generally (in such a way as to ensure certain action) to all the rolling stock that would come together on our various lines, on account of the endless shapes and sizes of the carriages, and there are many other practical disadvantages connected with them, such as excessive friction, the liability to stick fast from disuse, ex posure to weather, &e. Sound signals emanating from each separate carriage would offer very great advantages if they could be made to answer in practice, each carriage would be independent of every other, and there would be nothing to think of when the train was put together or when carriages were detached ; but it has been demonstrated in practice that any such sounds, no matter how loud, within practical limits, would not be heard when the train was running at any speed ; not only would they not be heardin front, but even in the rear of the train, if it consisted of more than two or three carriages. The Railway Clearing House Committee of 1853 remark on this subject:—“ Several members of this committee have at various times conducted experiments, having sound for their basis, and the result has invariably been that no noise, however loud, or shrill, or con tinued, whether the sound was produced by compressed air, trumpets, or gunpowder, could be heard, even when the train was short, when there was a head wind, or when the speed of the train was considerable.” Captain Tyler also confirms this statement in his report to the Board of Trade. Sight signals only would presuppose the constant attention of the guard and engine driver; but it is difficult to suppose men always on the look out for signals that might not occur a dozen times in as many years. The French Commissioners dispose of these last two classes of signals very briefly, they say :—•“ Les Nos. 2, 3, etc., consistent des appareils visuels, ou sonorcs, places sur les voitures des voyageurs. Nous demon- trons que leur signaux visuels, ne seraient point vus, que leur signaux sonorcs no seraient point enteudus.” We have already noticed the difficulty of providing a means for a guard to pass along a train in motion, whether we would effect it by a pas sage through the body of the train or by means of footboards on the outside: we will therefore pass on to the 8th class of expedients, that is to say, Reflectors placed so as to reflect the sides of the train on mirrors fixed to the guard’s van or engine. So far as it goes, this contrivance has been found to answer, and has long been in use on the “ Montpellier a Cette Rail way,” in France. The most disagreeable feature it possesses to passengers undoubtedly is the liability of being watched by persons who are not themselves visible. A great deal of clean ing and polishing is needed to keep the reflectors and mirrors in working order, and the system is entirely useless in tunnels and fogs, and also at night, unless the train were specially illuminated. It is moreover doubtful if either the guard or engine driver would constantly be in such a position as to see at once that anything was wrong. We now come to the Electrical systems of signalling through trains. The Railway Clearing House Committee of 1853 do not speak very favourably of the employment of the electric fluid, considering “that the apparatus used for evolving and conducting it is far too delicate for the rough usage and the disturbing causes to which they would be exposed when trains are in motion.” Since this time, however, the means of mani pulating and controlling this subtle agent have been greatly improved. There are several electrical systems which have been submitted to the test of actual practice on our various lines of railway. The two which hitherto have given the most satisfactory results are those used on certain trains on the South Western and London and North-Western Railways, invented by Mr. Preece and Mr. Martin. There is also a system invented by Mr. Walker used on the South-Eastern Railway, and one much used in France, invented by M. Prudhomme. There must necessarily be a great deal of simi larity in the action of all the electrical systems in use, the differences being principally in the greater or less simplicity of details, or of convenience in the carriage fittings and couplings adopted. All the plans are worked on the same electrical system, viz., that known as “ current equilibrium,” first adopted by Mr. Preece on the South-Western Railway. The apparatus used by Mr. Preece we will presently describe in detail. “ Current equilibrium ” may be explained as follows :—If at various points in an insulated wire the similar poles of equal batteries be attached, the opposite poles being connected with the earth, equilibrium will be established, and the batteries will remain inactive. But if any point of the insulated wire be now put to the earth, a is at once created which can be made to act on a bell or other apparatus. In consequence of instructions issued by the Board of Trade in November last, certain experiments have been carried out during the winter for the purpose of testing the feasibility of the various electrical systems of passenger communication, and Colonel Yolland’s exhaustive report on the subject is now before us. The systems tried were Mr. Preece’s on the South-Western and Midland, Mr. Walker’s on the South-Eastern, and Mr. Martin’s on the North-Western. On the South-Western the system had been very satisfactorily at work on the Exeter ex presses for nearly three years. In the special experiments recently conducted 48 double journeys were made, giving a mileage of 21,096 miles. The general instructions issued were that the trains should be started from all the stopping stations by the rear guard using the apparatus, careful daily accounts being kept of the working. Only seven failures are recorded (most of which are satisfactorily accounted for), and Colonel Yolland reports the experiments on this line to have been most satisfactory. On the Midland, where the same system was used, the difficulties were greater; owing to the great inter change of rolling stock on the journeys, the apparatus was very severely tested, and although many failures took place, the result, on the whole, is reported satisfactory. On the South- Eastern, where Mr. Walker’s system was used, three trains were fitted. These trains ran 324 journeys of 88 miles, giving a total mileage of 28,512 miles. Eight failures are reported. Considering the few stoppages and the very small interchange of rolling stock on this line, the number of failures is propor- tionathly high. On the London and North-Western one train was fitted, which made 25 double journeys of 125|- miles, in all 6287 miles, 3 failures are spoken of, and the trials are reported satisfactory. With regard to the possibility of establishing and maintaining electric communication throughout the entire length of a railway train, Colonel Yolland thinks it is im possible to doubt that it can be done; but in order to keep such a system in working order, he advises that the apparatus should be constantly used for starting trains. We will now briefly glance at the electric system applied