Page:Report from the Select Committee on Steam Carriages.pdf/219



Mr. John Macneil. 6 September, 1831. ble, but that part of the resistance arising from the friction and penetration of the wheels into the surface materials, would much depend on the construction of the Carriage, and its wheels, and the different sorts of roads over which it was drawn. In order to ascertain the average draught of a Carriage of 42 cwt. 16 lbs. over the above road. I conceive that the friction of the surface or resistance opposed to the motion of such a Carriage, should be ascertained on each description of road within the above limits, and then by knowing the rates of acclivity, or the amount of gravity acting on each, the average draughts might be ascertained, if the same Carriage and wheels were used, but loaded so as to make up 42 cwt. 16 lbs. the average draught. It might probably be calculated pretty nearly from the following Table of Experiments, which as it may be of use in the present inquiry. I here, beg leave to hand in; but it must be remembered that the proportions given in this Table between the increase of weight and the increase of draught, will not be the same on every description of road. To be enabled to answer the second part of the question, it will be necessary to know the rate of acclivity on which the draught of the Carriage weighing 21 cwt. 16 lbs. was 343 lbs., and also to know the draught of the four ton Carriage on the horizontal; but even then a difference might arise from the construction of the Carriage, and the situation of its centre of gravity.