Page:Report from the Select Committee on Steam Carriages.pdf/208



Mr. J. McAdam. 25 August, 1831. upon by the Commissioners of the Metropolis Roads, but upon a bard and well consolidated road a very great weight may be sustained without doing comparatively any injury.

When you state that if Steam Carriages come into general use harder materials ought to be used, you suppose that these Steam Carriages will be much heavier than the Carriages used at present?—Yes; I contemplate that they will carry much greater weights.

Your answer does not apply to Carriages that are of the same weight as those now used?-No; but to Carriages of the weight of eight or ten tons; when I spoke of the weight of from eight to twelve tons. I supposed a Carriage with four wheels.

Upon the present well constructed roads what weight do you think could be put upon them without crushing them?—I should not apprehend any injurious result from the general use of Steam Carriages with properly made wheels, carrying upon an average from eight to ten tons.

Your answer refers to roads that are so well made that the whole pressure shall be as that of an arch, but on the average of roads, such as shall be found in the country, would you give the same answer?—No, certainly not.

Taking the average of any line of road for a great number of miles, where materials less capable of bearing weight must necessarily be used for a considerable proportion of that road, what should you say is the maximum weight that should be allowed with reference to the preservation of that road on any one wheel of four inches and a half?—Two tons. Have you ascertained that by experiment?-I have not had an opportunity of judging of it, except in all the Waggons that depart from the Metropolis that are required to have the wheels constructed in the way I have described, some of which carry considerable weights.