Rambles on Railways

by Sir Cusack P. Roney

The results of Captain Tyler’s experiments with No. 2 engine were as follows:—Although at the time that they took place she was not in the best order, she was, nevertheless, able to ascend the incline, with the same load as had been attached to engine No. 1, in 6¼ minutes, or at the rate of 17⅓ kilometres (nearly 11 miles) an hour. This engine besides possessing a greater amount of boiler-power, travelled more steadily than No. 1; its machinery is more easily attended to, and the pressure of the horizontal wheels upon the centre rail can be regulated by the engine driver at pleasure, from the foot plate. The pressure employed during the experiment was 2½ tons on each horizontal wheel, or 10 tons altogether, but the pressure actually provided for, and which may, when necessary, be employed is 6 tons upon each, or 24 tons upon the four horizontal wheels. When this engine had ascended the experimental line in 6¼ minutes, or at the rate of 17⅓ kilometres per hour, the steam pressure in the boiler had fallen from 112 to 102½, and 3 inches of water in the gauge glass. The engine exerted, including the resistance from curves, 195 horses power—nearly 12 horses power to each ton of its own weight, or about 60 horses power in excess of what would be required to take up the load of 16 tons, over the same gradient and curves, at the rate of 12 kilometres per hour.

Captain Tyler finally reduced the pressure to 40 lbs. on the square inch, that is to one-third of the maximum pressure, and when he had done this, he found that the engine alone could move on a gradient of 1 in 12; the resistance of waggons and carriages being proportionally much less than that of a locomotive, the latter could a fortiori, draw a train with a gross load three times its own weight, or 48 tons upon the same gradient, the pressure of course being raised to 120 lbs. to the square inch.

A very important, and we believe an unexpected feature of the Fell system was immediately developed in the experiments; M. Desbriere calls special attention to it. The centre rail not only aids the train in going round curves, but also adds largely to its safety. Each vehicle is provided with four horizontal pulleys, each of about eight inches diameter, playing around vertical axes fixed upon the frame of the vehicle, and placed two and two at each of its extremities, and on each side of the centre rail. By the tightening of these pulleys, the flanges of the wheels, instead of gliding along the outer rails, press strongly against them, and thus the train is able to overcome curves unaccomplishable by any other means. This arrangement of parts also renders it impossible for either engine or vehicles to get off the line; all the more important, seeing that by the terms of the concession, the portion of the roadway ceded to Mr. Fell is, for the most part, on the outside, that is, the side nearest to the precipice, the bottom of which is, in many places, eleven or twelve hundred feet deeper than the roadway.

Before proceeding to extract from the Reports of the French Commissioners to their government their opinions upon the Fell system, it is desirable to give some general deductions which Captain Tyler makes from what he witnessed, as bearing upon the important general question of railways over mountain passes.

Hitherto the immense cost of the construction of such railways, and the immense cost of working them, have proved all but an effective barrier to their adoption. The cost of construction divides itself into two portions, and we will illustrate our meaning in the following manner:—Let us take A and B as the bases respectively on each side of a mountain. Were we to take these two points and to measure the interval between them, according to the every day application of the words “as the crow flies,” we must first take our crow perpendicularly up from A, to the exact height of the highest point which a person would be obliged to ascend, in order to cross the mountain, and then having drawn our imaginary tape to the point perpendicularly above B, we have the distance between them “as the crow flies.” But this distance in no way represents the actual distance that a person has to trudge up the mountain, and then to trudge down again in order that he may get, matériellement et physiquement, from one side of it to the other. The road which he has gone along can only be constructed with gradients that man and beast can accomplish. Exceed those gradients and the road might as well not be constructed. 1 in 12, or 440 feet in an English mile, is about as much as ought to, or, indeed, can be accomplished in this way. Yet, even to attain a mountain road with this gradient, it is necessary to make a great many turns and twists, to tunnel here, to raise an embankment there, to span a gorge sometimes several hundred feet deep with a bridge built between two projecting craigs at opposite sides of the ravine, whilst other bridges, of almost adamantine strength, and hundreds of feet in length, are often barely sufficient to resist the giant force of the torrents that dash along the gorge, and at times rise to within a few inches of a bridge’s level. And when the road is finished, at the heavy cost which all such works involve, and traffic is brought upon it, its length is very different from what it would have been if it could simply have been climbed up the mountain by the shortest and straightest possible way, and then been brought down again in the same manner. Still greater will be the difference between it and what our friend the crow accomplishes in the flight we have just referred to.

The experience acquired by our engineers tells us that the very maximum gradient an engine on the ordinary principle can climb up is 1 in 25, or 211 feet in a mile, but this can only be for a few yards, and with what is known, in locomotive language, as “a good run at it.” On the Sœmmering, as has already been stated, the average gradient on the north side is 1 in 47, or 111 feet in a mile; on the south side 1 in 50, or 105 feet in the mile; yet these gradients, favourable as they are, compared with the gradient of an ordinary roadway over a high mountain pass, could only be obtained at a cost of £98,000 a mile. Equally costly was the Giovi incline, constructed to surmount the Apennines near to Genoa. The worst gradient on it for a short distance is 1 in 29, or 160 feet in a mile; its best 1 in 50, or 106 feet in a mile. The ruling gradient of the beautiful railway over the Apennines between Pistoja and Bologna is 1 in 40, or 132 feet to the mile. The distance from Pistoja at the foot of the mountain on the east to Poretta at the foot of the mountain on the west, by the old road, is 25 “chiliometres” (kilometres), a little more than 15½ English miles, but in order to obtain for the railway the average gradient of 1 in 40 we have just mentioned, it has been necessary to extend the distance from 25 chiliometres to 40, equal to 25 English miles. Each of these 40 chiliometres has cost 1,000,000 francs, or £40,000, making the total cost of the railway independent of the special rolling stock for working it, £1,600,000, or at the rate of £64,000 a mile. If at the time that Mr. Fell was engaged in connection with the construction of this very fine work, he had had his ideas matured respecting the centre-rail system, and that consent had been given to the line being laid down in accordance with it, the distance to traverse would have only been 15½ English miles; many expensive works would have been avoided, and the total cost of the line would not have exceeded £400,000—probably it would have been considerably less. Another matter worthy of consideration is, that this Apennine Railway consumed eleven years in its construction. Not very protracted, considering that there are nearly 7 miles of tunnels (39 in number), of which 23 are on the ascent from Pistoja, and 16 on the descent to Poretta. The longest is 1⅞ mile, the second longest 1⅝ mile, the length of the others is pretty nearly equal. Nearly one-eighth of what is not tunnel is bridge or viaduct; some of the latter across ravines 300 to 400 feet long, and nearly 180 feet high. They are, in fact, double viaducts, one built on the top of the other, and reminding one of the two tiers of guns of an old-fashioned two-decker. According to the testimony of M. Desbriere, Mr. Fell would have accomplished an equally efficient railway on or through the pass in a couple of years. He would have had no tunnels, unless when, occasionally, he might want to get by a short cut through a projecting ledge of rock or mountain instead of round it, and, as to bridges and viaducts, a twentieth part of those now existing would have amply sufficed him. Before quitting this subject, we would observe that Captain Tyler sets down the difference between the length of a mountain road with gradients of 1 in from 12 to 15 as one-half that of a roadway with gradients of 1 in 40. In practice, however, it will probably be found that the difference will hardly be so great—but there can be no doubt of its not being less than as 3 to 5.

Taking the question of working expenses, we know that on the Sœmmering, on the Giovi, and on the Pistoja lines, the weight of the engines is about fifty-five tons, and that on the Sœmmering and the Giovi the cost per train mile is 6s. 2d. down the pass as well as up it, while the average cost on the ordinary portions of the lines is under 3s. a mile; and so oppressive is the working cost of goods trains over the Sœmmering felt to be, and with such uncertainty are the trains, but especially the goods trains, worked over the pass, that before the end of the present year, a railway between Vienna and Trieste will be opened, with a detour of 110 miles, and it is by this roundabout line that the immense and continuously increasing goods traffic between the interior of Austria and its great naval and commercial sea port, will eventually be conveyed to it.

Captain Tyler, whilst instituting a comparison between the cost of the construction and working of the Mont Cenis Over-ground Railway with these costs upon the railway through the Great Tunnel of the Alps, calls especial attention to the fact that the former is only laid down on a road-bed already in existence, as a temporary (that is if we can accept temporary as an exact translation of provisoire) line, whilst that through the tunnel is permanent. But keeping this point in view, the report of Mr. James Brunlees, C.E., the distinguished engineer of the Mont Cenis Railway Company, shows its cost to be (including the necessary engines and other rolling stock) a little under £8,000 a mile, whilst he asserts that the Tunnel line will probably cost, including interest at 6 per cent, during construction, but not the cost of special engines and other rolling stock, £7,000,000, or £140,000 a mile. As the cost of the tunnel and its accessories is dealt with subsequently at full length, we need only here remark that Captain Tyler considers the cost of an over-ground permanent Fell line, laid down on an already existing Alpine roadway, with the ordinary 4 feet 8½-inch gauge, and with curves of radii varying from 150 to 180 yards, should not exceed three times the cost of the present provisional road, or about £21,000 a mile. We are disposed to concur completely in this estimate, provided the additional width that it would be necessary to give to the roadway could be obtained by excavating from the inner side of the road, and not by widening it on its outer side—the side of the precipice—for this latter could only be effected by the construction of numerous solid and very expensive abutments in masonry, requiring great tact, nicety and judgment in their adjustment.

Captain Tyler concludes his report to the Board of Trade as follows:—

“As the results of my observations and experiments, I have to report, in conclusion, that this scheme for crossing the Mont Cenis is, in my opinion, practicable, both mechanically and commercially, and that the passage of the mountain may thus be effected, not only with greater speed, certainty, and convenience, but also with greater safety than under the present arrangements. Few would, in the first instance, either contemplate or witness experiments upon such steep gradients and round such sharp curves on the mountain side, without a feeling that much extra risk must be incurred and that the consequences of a fractured coupling or a broken tire, or a vehicle leaving the rails, would on such a line be considerably aggravated.