Page:Report from the Select Committee on Steam Carriages.pdf/136



Mr. Richard Trevithick. 12 August, 1831. Do you conceive that your Engine, of which you have produced a plan, is as applicable to Carriages on roads as to the propelling Engines at sea?—Yes, that is one object I have in view, and for agricultural purposes, for ploughing, and every other purpose.

Have you ever calculated what the weight of a Carriage would be with one of your Engines?—Yes; I am looking to see the necessity of the doing away with the supply of water that I have done away with; but in dispensing with the water I shall save three-quarters of the fuel; every time we double the force of Steam we save seventy-five per cent, upon it. This Engine, I conceive, will not take one quarter part of the fuel; one charge of water will do for a month. I have just taken out a patent for my Engine.

Do you condense with a sufficient rapidity to take from the piston the pressure of the returning steam?—Yes; there was an Engine which had been working with high steam and one of my boilers, and the cylinder was inclosed with brick-work, to keep off the external air; while I was abroad they took down the brick-work, and set it at a distance from the cylinder of four or five inches, and turned the draught from the fire round the cylinder to keep it off, and from that made more than sixty per cent, difference in the fuel; if the Engine was doing forty millions to a bushel of coals before, it then did sixty-three millions, and they burnt five bushels of coals to keep the cylinder hot; if they had put that under the boiler, it would have done forty millions, as before; but in putting in five bushels round the boiler, it did three hundred and fifty-six millions; then the difficulty was to know how it would make that difference; I could not at first make it out; however it turned out afterwards how it was, and it was the steam; when coming in upon the piston, the cold sides of the cylinder took out a part of the heat; these are single Engines; the steam is returned under the piston upon the Engine going that stroke again; the cold sides of the cylinder caused a dew by the steam; the steam was expanded to full four times the space; by the time it had gone a quarter part it was shut; then it was