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.