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] [Illustration: 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.” [Illustration: PATENT CENTRE-RAIL ENGINE. FRONT ELEVATION.] “On the 20th of January, 1863, Mr. Fell took out his first patent, and on the 16th December, of the same year, his second, under the modest title of ‘improvements in locomotive engines and railway carriages.’ In neither of these patents did Mr. Fell attempt to appropriate to himself the invention of the centre rail, but simply the means, both ingenious and practical, by which he has succeeded in applying the principle of additional adhesion.”