As previously stated, the experiments on the Liverpool railway, were made with carriages having springs to support their weight; the experiments on the Darlington railway were made on carriages without springs, and as the latter appeared to have less friction, such a diminution of resistance might be attributed to the want of springs; an experiment was made on the Darlington railway by Mr. Dockray, to ascertain if such was the case. A carriage with springs was taken and tried upon the same plane, and the friction was found to be 8.35 lbs. per ton; the same waggon was tried with the springs wedged up, so as not to act, when the friction was found to be 8.58 lbs. per ton; giving a trifling result in favour of the use of springs. §7.-Tables of the Resistance of Carriages, on different Gradients on Railroads. Although the experiments with trains of carriages upon the Liverpool and Manchester railway give 8.03 lbs. per ton, as the friction of the intermediate carriages, and as the engine precedes the train of carriages, and, therefore, prevents the wind from acting upon them, that has been taken as the friction by M. Pambour; we think, however, in practice, this will be found to be too favourable a result, and that eight and a half, or nine pounds per ton will be more likely to be found to be the real amount of friction. We have, therefore, given two tables, shewing the amount of friction upon planes of different gradients, calculated at the 240th part of the weight, or about nine pounds per ton; and also the 280th part of the weight, or eight pounds TABLE XIV. Shewing the resistance of a carriage, on different inclinations of plane. Friction equal to the 240th part of 30 *0375 '01185 *00851 *00719 *00649 '00605 * 00574 06 888 70 '0185 '01001 99910. '01527 '00975 *00942 *00774 8900. 64900. 98900. 98400. 10800. 91800. *00702 88900. 00598 *0057 '00693 '00634 '00594 89900. *00592 '00565 *00577 *00555 '00538 *00525 *00523 '00522 '00520 '00519 *00624 '00588 *00563 *00544 *0053 *00518 19400. '00672 *0062 *00586 *00561 *00543 *00529 *00517 0 TABLE XV. Shewing the resistance of a carriage, on different inclinations of plane. the weight, or 8 lbs. per ton. Inclination of the plane, equal to 1 in Friction equal to the 280th part of The following experiments were made, to ascertain the resistance of carriages moved along the plate rail, with the same dynamometer used in the experiments made upon the Killingworth railway. TABLE XVI. The rails were each four feet long, and 3 inches broad, where the wheel runs upon them; and the height of the upright ledge three inches. From these experiments, we find the resistance of a loaded carriage, weighing 8512 lbs., to be 73.5 lbs., which is equal to the 116th part of the weight; and, comparing this with No. 2. Experiment IV., which had the same kind of bearing, we find the relative resistances of the plate to the edge-rail, as 73: 63, which gives the most decided preference to the latter. CHAPTER VIII. FRICTION OF ROPES USED BY FIXED ENGINES ON RAILROADS. § 1. Different Experiments on the Friction of Ropes. ROPES being generally used, as a medium of communication between the moving power and the resistance, in dragging carriages up acclivities, along level planes, or for lowering them from one level to another upon railroads; it is not only interesting, but, in the case of the self-acting planes, absolutely necessary, that a proper estimate of their friction should be obtained. In fixed engines, where loads are dragged forward upon carriages by means of opes, unless we can calculate, à priori, the friction or resistance opposed by the use of such rope, we are at a loss to know how much engine-power is required to overcome the resistance, and to obtain the requisite velocity ;-we may, by over-rating its effects, load the engine with unnecessary strength and power, or, by under-rating, erect an engine not adequate to perform the desired effect. In self-acting planes, where gravity is the moving power, it scarcely need be stated, that the strictest regard should be observed in economising its effects; the power itself is acquired at no cost; and, on that account, its action should be extended to the utmost limit of its applicability. The following experiments are selected, from a great many which we have been allowed to make upon the different railroads in the neighbourhood of Newcastle |