A vehicle for the transport of persons and goods by land. Although the varieties of carriages are very great, yet they may be ranged under two heads, viz. sledges, or carriages without wheels, and wheeled carriages. The earliest carriages were doubtless of the first class, or without wheels; and although they are now very generally superseded by carriages mounted upon wheels, and indeed have become nearly obsolete in this country yet they are still extensively used in the more northern parts of Europe, where the ground is for a considerable portion of the year covered with snow, and the rivers frozen over so as to allow carriages to travel upon them. In these cases sledges are found superior to wheel carriages, as the friction upon the surface of the snow or ice is small, and as, from the greater extent of bearing surface, they do not sink so deep as wheel carriages, in which the whole weight presses upon two, or at most, four points. The motion is also found to be much more easy, as from their length of bearing they do not rise and fall with every slight inequality in the roads, in the manner of wheel carriages.
But for general purposes, and on roads composed of rough materials, which offer great resistance to bodies sliding over them, it is found highly advantageous to pi lace the carriages upon wheels, as by this means the sliding motion is converted into a rolling motion, and the rubbing surfaces, when the friction takes place, are reduced in the proportion of the diameter of the wheel to that of its axle, and the friction is still further reduced by the rubbing surfaces being polished, and admitting of lubrication, which tends materially to diminish friction. The friction being diminished in proportion to the difference between the diameters of the wheels and the axles, it is evidently advantageous to employ wheels of large diameter, which are also beneficial in another respect, as they experience less resistance from the inequalities of the surface over which they roll, as the leverage to which the power of the horse is applied, is as the diameter of the wheel; and as any obstacle on a road will sooner come in contact with a large wheel than with a small one, in consequence of the curvature of the former being flatter than that of the latter, so the power by which the wheel is drawn over the obstacle is exerted through a greater space with the large than with the small one.
We shall endeavour further to explain this by a little diagram. Let the circle a represent a small wheel, whose axle is at b, and c a stone lying in the road, over which the wheel is to pass; and the dotted circle to represent a large wheel, whose centre is at f; now the obstacle k is already in contact with the large wheel, but the small wheel has not yet arrived at it: the horse would therefore move through a greater space in bringing the centre of the large wheel perpendicularly over the obstacle, than in bringing the centre of the small wheel over the object after it had come in contact with the periphery; thus the horse exerts more power, or what is the same, exerts the same power through a greater space with the large wheel than with the small one. And again, as the angle k f h, at which the obstacle k interrupts the large wheel, is the same as the angle c b d, at which the obstacle c interrupts the small wheel, the same force which will draw the small wheel over the obstacle c, will, by the increased leverage, draw the large wheel over the obstacle k. The advantages above attributed to large wheels over small ones are not merely theoretical, but have been confirmed in a variety of instances in practice.
We therefore insert the diagram on the following page, exhibiting a method of applying hind wheels of larger diameter than ordinary to waggons, without carrying the floor higher than usual. a a represents the hind wheels; b b the bended axletree, of a crank form, passing under the bed of the carriage, which lies between the two extremities of the axletree, and permits the floor of the carriage to lie close to the upper side of the axletree, the floor being usually as much above the latter as the thickness or depth of the bed. The modes by which carriages are or have been propelled are various - as the force of animals, of wind, of men, exerted upon machinery contained within the carriage, and that of steam. Carriages propelled by wind acting upon sails are not common for land travelling, although such have been constructed; but in some parts of Holland, boats mounted upon long skids are frequently employed for sailing over the ice, and have sometimes been known to go at the rate of eighteen miles per hour. In 1826 a patent was obtained by Col. Viney and G. Pocock, for a carnage, to be impelled by the force of the wind acting upon one or more kites attached to the carriage, which they denominated the "Charvolant." It is represented in Fig. 2 in the engraving on the following page.
The kite, a, Fig. 1, is jointed in the middle, that it may be folded up, and carried or stowed away with greater facility, b b b b are four cords for regulating the position of the kite, and to assist the steerage; they are brought together by passing through the dead eye c, whence they proceed to the carriage, where they are regulated to the proper lengths by the persons therein. By shortening the cords on the right-hand "side of the kite, the car may be turned to the right, and by shortening the left-hand cords it will be turned to the left. But the charvolant, by the cross handler and stem e f, which acts on the axis of the fore wheels by means of an endless band or cord passing about a pulley f fixed on the lower end of the stem e f, and the pulley g fixed on to the bed of the axletree of the fore wheels. The machine is stopped, or its motion retarded by the drag k, which is attached to the perch by a spring to keep it off the ground till it is required to retard the motion or to stop the carriage, when the fluke end is pressed into the earth by the lever h acting on the connecting piece i.