Page:Report from the Select Committee on Steam Carriages.pdf/130



Mr. Richard Trevithick. 17 August, 1831. steam, and a safety valve of five times the size would give no relief, or not in time; a proof that a high-pressure Steam Engine boiler has not been broken generally by the pressure of the high steam, but from being heated, is because the portable gasholders are about ten inches diameter, and the sixteenth of an inch thick, and they are charged with 30 atmospheres, or 450 lbs, each without accident; an accident never happens to them, and the pressure is not so great as on half of the strength of iron; the boilers of Steam Engines in Cornwall have hurst that have not been loaded to an eighth part of that pressure for the same substance and size of boilers; therefore that is a proof that they must have been broken by the heating of the boiler, and suddenly cooling it by a sudden expansion. The gasholders have never been heated and have never been injured; I have known instances where by turning cold water into a red-hot boiler they have exploded. An Engine I had the care of was injured by the neglect of one of the enginemen in that way. The boilers to the high-pressure Steam Engines on my construction are cylinders, one in the other, the inner cylinder containing fire, and the outer cylinder surrounds the water and leaves a space of about a foot between the two tubes for water. Where they have been neglected the fire-tube bas been made red-hot, and the splashing of the water over the hot tube from the ebullition occasioned by the escape of steam has burst the boiler by the water flowing over the red-hot sides, and generating steam faster than it can be discharged.

By neglected you mean that the tubes were not completely covered with water?—They are not covered with water. With my inferential Engine, that never can be the case.

Have the goodness to state to the Committee your opinion with respect to the wear of the road by Steam Carriages?—I think that the roads will not be injured so much by Steam Carriages in future as they have been, because there will be no need to chain the wheels; by putting the valve to the stop, the steam