steam, and if Mr. Watt has ever stated in any of his publications the effects of it, because if he condemns it in any of his writings, it will clearly show from that, that he did not know the use of it. Mr. Homfray, of this place, has taken me by the hand, and will carry both the engines and the patent to the test. There are several of Boulton and Watt's engines being taken down here, and the new engines being erected in their place. Above 700 horse-powers have been ordered at 12_l._ 12_s._ for each horse-power for the patent right, and the persons that ordered them make them themselves, without any expense to me whatever. If I can be left quiet a short time I shall do well, for the engines will far exceed those of Boulton and Watt. The engine at Greenwich did fourteen millions with a bushel of coals; it was only an 8-inch cylinder, and worked without an expansive cock, and under too light a load to do good duty; also on a bad construction, for the fly-wheel was loaded on one side, so as to divide the power of the double engine, and connected to the pump-rods on a very bad plan. I remember that Boulton and Watt's 20-inch cylinders when on trial did not exceed ten millions; I believe you have the figures in your keeping. Let us have the 60-horse power at work that is now building, and then I will show what is to be done. It will be loaded at 30 lbs. to the inch on each side the piston, it has an 8-feet stroke with an expansive cock, and the blowing cylinder directly over the steam-cylinder, as free from friction as possible. There was no engine stopped on account of this accident; but I shall never let the fire come in contact again with the cast iron. The boiler at Greenwich was heated red hot and burnt all the joints the Sunday before the explosion. "I have received a letter from a person in Staffordshire who has a cylinder-boiler at work with the fire in it, and he says the engine performs above all expectation; he requests me to give him leave to build a great many more. I shall put two steam-valves and a steam-gauge in future, so that the quicksilver shall blow out in case the valve should stick, and all the steam be discharged through the gauge. A small hole will discharge a great quantity of steam at that pressure. There will be a railroad-engine at work here in a fortnight; it will go on rails not exceeding an elevation of one-fiftieth part of a perpendicular and of considerable length. The cylinder is 8-1/2 inches in diameter, to go about two and a half miles an hour; it is to have the same velocity of the piston-rod. It will weigh, water and all complete, within 5 tons. "I have desired Captain A. Vivian to wait on you to give you every information respecting Murdoch carriage, whether the large one at Mr. Budge's foundry was to be a condensing engine or not. "Is it possible that this engine might be burst by gas? "I am, Sir, "Your very obedient servant, "RICHARD TREVITHICK."