While the steam-carriage was being exhibited, a gentleman was laying heavy wagers as to the weight which could be hauled by a single horse on the Wandsworth and Croydon iron tram-way; and the number and weight of wagons drawn by the horse were something surprising. Trevithick very probably put the two things together—the steam-horse and the iron-way—and kept the performance in mind when he proceeded to construct his second or railway locomotive. In the mean time, having dismantled his steam-carriage, sent back the phaeton to the coach-builder to whom it belonged, and sold the little engine which had worked the machine, he returned to Camborne to carry on his business. In the course of the year 1803 he went to Pen-y-darran, in South Wales, to erect a forge engine for the iron-works there; and, when it was finished, he began the erection of a railway locomotive—the first ever constructed. There were already, as above stated, several lines of rail laid down in the district for the accommodation of the coal and iron works. That between Merthyr Tydvil and Cardiff was the longest and most important, and it had been at work for some years. It had probably occurred to Trevithick that here was a fine opportunity for putting to practical test the powers of the locomotive, and he proceeded to construct one accordingly in the workshops at Pen-y-darran.
This first railway locomotive was finished and tried upon the Merthyr tram-road on the 21st of February, 1804. It had a cylindrical wrought-iron boiler with flat ends. The furnace and flue were inside the boiler, the flue returning, having its exit at the same end at which it entered, so as to increase the heating surface. The cylinder, 4-3/4 in. in diameter, was placed horizontally in the end of the boiler, and the waste steam was thrown into the stack. The wheels were worked in the same manner as in the carriage engine already described; and a fly-wheel was added on one side, to secure a continuous rotary motion at the end of each stroke of the piston. The pressure of the steam was about 40 lbs. on the inch. The engine ran upon four wheels, coupled by cog-wheels, and those who remember the engine say that the four wheels were smooth.
TREVITHICK'S HIGH-PRESSURE TRAM-ENGINE.
On the first trial, this engine drew for a distance of nine miles ten tons of bar iron, together with the necessary carriages, water, and fuel, at the rate of five and a half miles an hour. Rees Jones, an old engine-fitter, who helped to erect the engine, and was alive in 1858, gave Mr. Menelaus the following account of its performances: "When the engine was finished, she was used for bringing down metal from the old forge. She worked very well; but frequently, from her weight, broke the tram-plates, and also the hooks between the trams. After working for some time in this way, she took a journey of iron from Pen-y-darran down the Basin Road, upon which road she was intended to work. On the journey she broke a great many of the tram-plates; and, before reaching the Basin, she ran off the road, and was brought back to Pen-y-darran by horses. The engine was never used as a locomotive after this; but she was used as a stationary engine, and worked in this way for several years."
So far as the locomotive was concerned it was a remarkable success. The defect lay not in the engine so much as in the road. This was formed of plate-rails of cast iron, with a guiding flange upon the rail instead of on the engine wheels, as in the modern locomotive. The rails were also of a very weak form, considering the quantity of iron in them; and, though they were sufficient to bear the loaded wagons mounted upon small wheels, as ordinarily drawn along them by horses, they were found quite insufficient to bear the weight of Trevithick's engine. To relay the road of sufficient strength would have involved a heavy outlay, which the owners were unwilling to incur, not yet perceiving the advantage, in an economical point of view, of employing engine in lieu of horse power. The locomotive was accordingly taken off the road, and the experiment, successful though it had been, was brought to an end.
Trevithick had, however, by means of his Pen-y-darran engine, in a great measure solved the problem of steam locomotion on railways. He had produced a compact engine, working on the high-pressure principle, capable of carrying fuel and water sufficient for a journey of considerable length, and of drawing loaded wagons at five and a half miles an hour. He had shown by his smooth-wheeled locomotive that the weight of the engine had given sufficient adhesion for the haulage of the load. He had discharged the steam into the chimney, though not for the purpose of increasing the draught, as he employed bellows for that purpose. It appears, however, that Trevithick's friend, Mr. Davies Gilbert, afterward President of the Royal Society, especially noticed the effect of discharging the waste steam into the chimney of the Pen-y-darran engine. He observed that when the engine moved, at each puff the fire brightened, while scarcely any visible steam or smoke came from the chimney.
Mr. Gilbert published the result of his observations in "Nicholson's Journal" for September, 1805, and the attention of Mr. Nicholson, the editor, having thereby been called to the subject, he proceeded to make a series of experiments, the result of which was that in 1806 he took out a patent for a steam-blasting apparatus, by which he proposed to apply high-pressure steam to force along currents of air for various useful purposes, including the urging of furnace and other fires. It is thus obvious that the principle of the blast-pipe was known to both Gilbert and Nicholson at this early period; but it is somewhat remarkable that Trevithick himself should have remained skeptical as to its use, for as late as 1815 we find him taking out a patent, in which, among other improvements, he included a method of urging his fire by fanners, similar to a winnowing machine.
In the mean time Trevithick occupied himself in carrying on the various business of a general engineer, and was ready to embark in any enterprise likely to give scope for his inventive skill. In whatever work he was employed, he was sure to introduce new methods and arrangements, if not new inventions. He was full of speculative enthusiasm, a great theorist, and yet an indefatigable experimenter. At the beginning of 1806—the year after the locomotive had been taken off the Merthyr Tydvil tram-road—he made arrangements for entering into a contract for ballasting all the shipping in the Thames. At the end of a letter written by him on the 18th of February in that year to Davies Gilbert, respecting a puffer engine, he said, "I am about to enter into a contract with the Trinity Board for lifting up ballast out of the bottom of the Thames for all the shipping. The first quantity stated was 300,000 tons a year, but now they state 500,000 tons. I am to do nothing but wind up the chain for 6d. per ton, which is now done by men. They never lift it above twenty-five feet high—a man will now get up ten tons for 7s. My engine at Dalcoath has lifted about 100 tons that height with one bushel of coals. I have two engines already finished for the purpose, and shall be in town in about fifteen days for to set them to work. They propose to engage with me for twenty-one years."[16] The contract was not, however, entered into. Trevithick quarreled with the capitalists who had found the money for the trials, and the "Blazer" and "Plymouth," the vessels in which his engines and machinery had been fitted, fell into other hands.