“ WHEEL (O. Eng. hwēol, hweohl, &c., cognate with Icel. hjōl, Dan. hiul, &c.; the Indo-European root is seen in Sanskrit chakra, Gr. κύκλος, circle, whence "cycle") , a circular frame or solid disk revolving on an axis, of which the function is to transmit or to modify motion. For the mechanical attributes and power of the wheel and for the modification of the lever, known as the "wheel and axis," and of the mechanical powers, see Mechanics. ”

“ The most familiar type of the wheel is of course that used in every type of vehicle, but it forms an essential part of nearly every kind of mechanism or machinery. Vehicular wheels in the earliest times were circular disks either cut out of solid pieces of wood, or formed of separate planks of wood fastened together and then cut into a circular shape. Such may be still seen in use among primitive peoples to-day, especially where the tracks, if any exist, are of the roughest description, and travelling is heavy. ”