"Mr. Uville wishes everything to be sent off as soon as finished, except the rolling engine, which is to remain until he arrives. We intend to leave Cornwall for Bridgenorth on Monday, November 1st. You may expect to see us three days after that date. The wheels ordered for the carriages are to run on the ground and not on railroads. Mr. Uville now wishes to have seventy-two instead of sixty as ordered before. "I remain, Gentlemen, "Yours, &c., "R. TREVITHICK. "MESSRS. HAZELDINE AND CO." The last-named engine was intended for the coinage operations in the Mint at Lima. The use of railway locomotion had been under discussion with the engine builders, and probably those particular carriage-wheels were ordered in the hope that the portable engine built for conveying itself from place to place in the sugar plantations of Jamaica, would in the Cordilleras be made to draw waggons on common roads. The hand sketch of the winding engine in the letter of the 11th October, was to correct an error in an order hastily given a month before; when, to save time, outline instructions for this complicated work were hurriedly sent to the manufacturer, that a commencement might be made while the more perfect detail drawings were being completed; the first-proposed position of the fly-wheel would prevent the engineman from conveniently reaching the four-way cock; Trevithick therefore suggested that the fly-wheel should be moved to the outside of the house, and a crank placed on the end of the driving shaft in lieu of the crank-pin in an arm of the fly-wheel. The sketch illustrating this change makes us fully acquainted with the kind of winding high-pressure steam-puffer engines of 8-horse power, with open-top cylinders of 12 inches in diameter and about 3 feet 6 inch stroke, sent to Peru in 1814. Steam, of 30 lbs. to the inch above the pressure of the atmosphere, was admitted under the bottom of the piston by a cock moved by an eccentric on the fly-wheel shaft; the gradual closing of the cock reduced the supply of steam when about one-third of the stroke had been made, wholly cutting it off some time before its completion, making it a high-pressure steam expansive engine. The movement of the cock then turned the steam from under the piston into the chimney blast-pipe, and the down-stroke was performed by the weight of the descending piston, made more than usually deep and heavy to prevent the tendency to twist in the cylinder from the angle of the jointed connecting rod, and also by the momentum of the fly-wheel and its balance-weight, moving at a speed of thirty strokes a minute. Its boiler was the Trevithick wrought-iron cylindrical, with internal tube and fire-place, but so arranged that if necessary the fire could be placed in brick flues under the boiler, returning through the tube.