Of the Formatton and Construction of Railways.—Whatever be the moving power to be used for the transport of loads upon a railway, its force must be proportioned to the average resistance of such loads, and it must be capable of va rying its to the same extent as that resistance is subject to variation. The great perfection which has been at Mined in the construction of the rails, and in the methods of fixing them in their position upon the road, is such that the resistance offered to the tractive pow er by loads moved on a straight and level railway may be regaided as practically uniform, so that the moving power by which a load is transported at a gives speed on a straight and level line of rail way is subject to a resistance as unvaried and as uniform as any to which moving powers are usually submitted in any of the processes of art ; but as the amount of resistance to the tractive powers upon a straight and level railway is diminished by the perfection thus attained in the construction of the road, so, in the same degree, is any resistance produced by a departure from a perfect level more sen sibly felt. Thus, if the resistance to the moving power on a straight and level railway, by a load moved at a given speed, be equal to the 250th part of the load, an acclivity which would rise at the rate of one foot in 250, or nearly at the rate of 20 perpendicular feet in a mile, would produce a resistance to the mov ing power by reason of the ascent alone, equal to a 250th part of the load,_ and there fore equal to the resistance a the mov ing power would sustain on a level line. It follows, therefore, that under such circumstances, in drawing a load up such an acclivity, the moving power would have to overcome twice the resistance opposed to it on a level ; for the same causes which produce on a level a resist ance amounting to the 250th part of the load equally produce this resistance in ascending the acclivity, in addition to which there would be an equal amount of resistance due to the ascent. If, therefore, under such circumstances, the moving power were required to draw the load up the acclivity at the same speed as that at which it drew it on the level, the machine exerting that power must be endowed with properties in virtue of which it is capable of varying its energy, without injury to its structure, in the proportion of two to one.
With reference to horse and steam power, Anderson observes, theta wagon horse with ease, under favorabk circum stances, draws 20 tons. Fulton says, that five tons to a horse is the average work on railways, descending at the rate of three miles per hour ; and one ton upwards with the same speed. Telford observes, that on a railway laid with a declivity of 50 feet in a milt., one horse will readily take down wagons contain ing 12 to 15 tons ; and bring back the same wagons with four tons. Wilkes states, that a horse drew down the de clivity of an iron road, 5 inches in 16 yards, 21 carriages or wagons, laden with coals and timberoveighing 85 tons, and the sane horse, up this declivity drew tons with ease. On a different railway, one horse drew 21 wagons of five cwt.
each, which, with their loading of coals amounted to 48 tons 8 cwt., down tilt declivity of 1 inch in three yards ; and he afterwards drew 7 tons up the same ; the hundred weight being 120 lbs.
Sylvester states that a moving force, which will give the velocity of 5 miles an hour, or 22 feet in 8 seconds, will be performed down a plane, 1 inch in 9 yards, or 1 in 324, by the engine making 45 strokes per minute (the circumfer ence of the wheel being nine feet), with a pressure of 91 lbs. upon an inch of each of the two the area of each being square inches. The weight of the engine and 16 wagons is equal to 154,560 lbs., nearly 70 tons.
If the same weight, at that speed, had to move on a dead level, and acquired the same velocity in one minute as before, the moving force would require to be 1781 lbs., which would require a pressure of 18.7 lbs. upon one inch. But after the speed is obtained, it will require only 7 lbs. to keep it moving at the same rate.
If the same load were required to move up the plane, it would require a moving force of 2828 lbs., or a pressure upon every square inch of 18.8 lbs. And this velocity would be kept up by a con stant pressure of 1447 lbs., which will be lbs. upon every inch of the piston.
When the engine is required to travel at the rate of nine miles per hour, the force necessary to overcome the weight 154,560 lbs. will be for the first minute, when the engine is travelling on a level, 2890•811bs.; when moving down the plane 2461.61 lbs. ; and, when moving up the plane 8320.01 lbs. But that, when the velocity is attained, a force that will balance the friction is sufficient to keep up the required velocity. This ioree is, for travelling on a level, 900 lbs.; for moving down the plane, 471 lbs.; and for moving up the plane 1829 lbs.
A boat weighing with its load 15 tons, and a wagon of the same weight, the one on a canal and the other on a railway, would be impelled at the following rates, by the following quantities of power—in pounds and in horse-power—reckoning one horse equal to 180 lbs.
The force required to keep a given weight in motion does not vary with the velocity : thus, a force of 14 lbs. was found to overcome friction, and keep in motion an empty coal-wagon, weighing 23.25 cwt. on a railroad ; but that, on doubling the velocity, no more force was required. Further, on increasing the weight, or load, the power required to overcome the friction, and keep the wagon in motion, did not increase in similar proportion, but up to 76.25 cwt. was about 1-14th less.
The following is a summary of railway i communication in Europe : From an analysis of railroads in Great Britain and Ireland, it appears that the number of miles of railroad open for use, on the 30th of June, 1850, was 5,447. The number of passengers conveyed during the preceding half year was 28,761,695. The number of persons killed on the railroads during that period was 86, and of persons injured 75. Of the persons killed, 12 were passengers, five of whom were killed from causes beyond their own control, and seven in conse quence of their own misconduct or want of caution. Of the other persons killed, 51 were persons in the employ of the railway companies or of contractors, and 21 were trespassers or persons in no way connected with the railroads, who lost their lives in consequence of improperly crossing or standing on the tracks.