The distance from St. Michel to Susa is 78½ kilometres—48¾ English miles. It is divided into two portions nearly equal in distance, but very different as regards gradient. For the first half of the distance the road continues to follow the valley of the Arq for twenty-five miles up to the village of Lanslebourg, which is situated at the foot of the Mont Cenis Pass, and here commences the second portion of the route forming the passage of the mountain.
Before proceeding farther we had better state that a French metre is equal to 3 feet 3·371 inches; consequently, 1,000 metres (or a kilometre) are equal to 1093·6389 English yards; an English mile is 1760 yards or 1609·31 French metres; 100 kilometres are 62¼ English miles; but a rough conversion of kilometres into English miles can always be made by multiplying the number of the former by 5 and dividing by 8; vice versâ to convert English miles into kilometres—multiply the number of the former by 8 and divide by 5.
In the 25 miles, or 40 kilometres, extending from St. Michel to Lanslebourg, there is only a rise of 670 metres, or 1,994 English feet. The steepest gradient is for 2½ kilometres (1½ miles) just beyond Modane at the French entrance of the great Tunnel of the Alps, of which we shall speak presently, the rise is 1 in 19, or 278 feet in the mile; and beyond Bramans, five miles farther, there is a rise of 1 in 20, or 264 feet in the mile, for 2 kilometres. The remaining gradients are as follows—1½ kilometre, 1 in 47; 8½ kilometres (5¼ miles) 1 in 60; 4½ kilometres (nearly 3 miles) 1 in 100; 7½ kilometres (4¾ miles) 1 in 108. In fact, with the exception of 4 kilometres (2½ miles) post-horses go at the trot over the whole distance between St. Michel and Lanslebourg. It is at this latter place that the real elevation of the pass commences, and the traveller who wishes to see a considerable portion of the ascent that is before him, can do so by taking a look out of the comfortless-looking, but, in reality, comfortable Hotel Imperial, the ground-floor of which is occupied as a refreshment room for passengers, and by Messieurs les Employés de la Douane Imperiale de la France. The frontier which separates France from Italy is exactly at the summit of the pass, and it is 10,500 metres or 6⅓ miles from Lanslebourg. In these 6⅓ miles it is necessary to mount 2,171 feet, or at the continuous rate of 350 feet in the mile. The gradient is consequently 1 in 15 in the whole of these 6⅓ miles. From the summit to L’Hospice, 4⅕ kilometres along the bank of the Cenis Lake, which yields capital trout six months in the year, and is frozen over for the other six, the gradient falls 1 in 25, or 211 feet in the mile. There is a short length of 3 kilometres to the Posting House of La Grande Croix, with a gradient of 1 in 60, or 88 feet in the mile. The severest gradient on the whole pass is in the next 10 kilometres (6¼ miles), 1 in 14, or 376 feet to the mile; and from Molaretta to Susa, 10⅓ kilometres (6½ miles), it is not much better, being 1 in 15, or 350 feet in the mile. There is a difference in the comparative elevations above the sea, of St. Michel and Susa of 715 feet, Susa being the lower of the two. Consequently, the Italian side of the pass is more precipitous than the French, for, whereas the total rise from St. Michel to the summit (a distance of 31 miles) is 4,165 feet, the descent from the summit to Susa (a distance of 18 miles) is 4,880 feet; in fact, the descent of the mountain only terminates as the town is entered. Of course, what are ascent and descent when going from France to Italy are reversed when coming in the opposite direction.
Mr. John Fell,[118] a gentleman about whom we have now to speak, has been occupied during many years of his life in the construction of railways and other works in Italy, being associated in several of them with Mr. Thomas Brassey, the eminent contractor, and other English gentlemen, among whom may be mentioned Mr. William Jackson, now M.P. for North Derbyshire. Connected with the laying out and subsequent construction of the magnificent railway between Pistoja and Bologna, by which the Apennines are traversed and overcome by the locomotive, Mr. Fell’s attention was directed to the mighty cost of construction of this railway, as well as of that across the Sœmmering and of the Giovi Incline, by means of which last-named, Genoa obtains railway connection with all parts of the Italian system. Reasoning and reflecting, Mr. Fell’s mind was, by a most happy incidence, brought to bear upon the effect that would be developed if the adhesion of the locomotive were increased by the application of horizontal wheels to a third or intermediate rail. But, in order to understand and to appreciate the full force of this conception, it is necessary to explain that the power or motive force of a locomotive is derived from two sources—the amount of steam evaporated and the amount of adhesion, or, as it is familiarly called, “bite,” that the wheels have on the rails. If a railway were completely level, it would only be necessary, in the construction of engines for working it, to make them with as little weight of material as possible, consistent with the strength and solidity required for their complete efficiency. But as a railway on, or very nearly on, the level, does not exist, it is necessary, in building engines, to give them such weight as, in addition to their steam power, will ensure them efficient adhesion upon the railway. On railways with favourable gradients the additional weight of engine is trifling; but exactly in proportion as gradients become unfavourable, so has it been found necessary to increase the weight of engines. Mr. Fell’s system increases adhesion without increasing the weight of the engines,[119] except to the very trifling extent of that appertaining to the four horizontal wheels, and the machinery connected with them. These horizontal wheels—two on each side of the engine—are made to rotate along the sides of the centre rail by identically the same steam that operates upon and causes the rotation of the perpendicular wheels upon the upper surface of the two ordinary rails. In this fact is contained the whole secret of the extraordinary development and marvellous increase of power which are obtained by the introduction of the centre rail, combined with the action of the horizontal wheels upon it.[120]
A CENTRE RAIL ENGINE AND TRAIN ASCENDING A GRADIENT OF 440 PER MILE WITH A CURVE OF 44 YARDS.
But before we go farther, let us endeavour to settle a question of priority as regards this invention or discovery, and we are able to do so all the more easily through the information furnished by Monsieur P. Desbriere at page 61 of his Etudes sur la Locomotion au Moyen du Rail Central, Contenant la relation des expériences entreprises pour la traversée du Mont Cenis. Paris 1865.
“Claims having been recently started,” says M. Desbriere, “as to the priority of the invention of the centre rail, we present the following historic resumé. The first patent taken out for its application was on the 30th of September, 1830, jointly by Messrs. Charles B. Vignoles, the eminent English engineer, and Ericsson, the Swedish engineer, the gentlemen who constructed the first monitors and marine engines to be driven by means of heated air. On the 15th of October, 1840, a patent was taken by Mr. Henry Pinkus, an English gentleman. On the 18th of December, 1843, Baron Seguier addressed a communication to the Academy of Sciences in Paris, in which he proposed, as a means of avoiding getting off the rails, the employment of a centre rail upon all railways, the gradients of which were moderate and the speed upon which was high. On the 5th December, 1846, a patent was taken out by the Baron for this system, of which he described himself the inventor, and of which he was at all events the very active promoter.[121] On the 13th July, 1847, a patent bearing upon the subject was taken out in England by Mr. A. V. Newton.”