Page:Report from the Select Committee on Steam Carriages.pdf/55



Mr. G. Gurney. 5 August, 1831. You have stated in your former Evidence that it would be unjust to put a toll on Steam Carriages according to the nominal horse power of the Engines, will you state why it would be unjust to put a toll in that way?—Because I conceive at present there is no standard by which we can fix a horse power:.

Will you state to the Committee the variations of rate at which the different Engineers have calculated horse power?—The most generally received standard is 180 pounds at two miles an hour, say from 150 to 200.

Could there be any fair system of toll established by the length of stroke, and the area of the piston?—I think not; the length of stroke and the area of piston will give power in proportion to the pressure of the steam upon it; the apparatus for supplying or generating the necessary steam would vary considerably in weight in different Engines; and therefore the weight of different Engines would vary so much perhaps as three times or four times.

Would there be any objection to placing toll on an Engine according to its greatest power of working?—I think it would be very difficult to ascertain its greatest power of working; it might be done, but it would be very inconvenient.

Are there no means of ascertaining the average power of working?—Horse-power is very arbitrary; the best standard which I can give, is the evaporation of water, and I should say that the evaporation of nine gallons of water in an hour, ought to be equivalent to one horse-power. One Engineer will apply the steam with more effect from nine gallons of water, and with more general advantage than another; nine gallons may be taken as an average.

What is the diameter of your cylinder, and what the length of stroke?—I believe I have given the length of stroke in my former Evidence, but not the diameter of the cylinder. The diameter of the cylinder now used is about eight inches, offering 64 circular inches area on the piston.

Is there not on those engines an average rate of expenditure, not speaking with mathematical