For this road Stephenson recommended wrought-iron rails, which were then costing £12 per ton--double the price of cast rails. The directors, however, stipulated that he should only buy one-half the rails required from the dealers in "malleable" iron. These rails weighed 20 pounds to the yard. After long hesitation, in the face of a serious opposition, the directors finally concluded to order three locomotives of Stephenson. The first, or "No. 1," engine (Fig. 52) was delivered in time for the opening of the road, September 27, 1825. It weighed 8 tons. Its boiler contained a single straight flue, one end of which was the furnace. The cylinders were vertical, like those of the earlier engines, and coupled directly to the driving-wheels. The crank-pins were set in the wheels at right angles, in order that, while one engine was "turning the centre," the other might exert its maximum power. The two pairs of drivers were coupled by horizontal rods, as seen in the figure, which represents this engine as subsequently mounted on a pedestal at the Darlington station. A steam-blast in the chimney gave the requisite strength of draught. These engines were built for slow and heavy work, but were capable of making what was then thought the satisfactorily high speed of 16 miles per hour. The inclines on the road were worked by fixed engines. [Illustration: FIG. 52.--Stephenson's No. 1 Engine, 1825.] On the opening day, which was celebrated as a holiday by the people far and near, the No. 1 engine drew 90 tons at the rate of 12, and at times 15, miles an hour. [Illustration: FIG. 58.--Opening of the Stockton and Darlington Railroad, 1815. (After an old engraving.)] Stephenson's engines were kept at work hauling coal-trains, but the passenger-coaches were all drawn for some time by horses, and the latter system was a rude forerunner, in most respects, of modern street-railway transportation. Mixed passenger and freight trains were next introduced, and, soon after, separate passenger-trains drawn by faster engines were placed on the line, and the present system of railroad transportation was now fairly inaugurated.