But this attachment must be mobile throughout in the horizontal plane. It should not be fixed on to the side of the ski-blade, or upon the ski in front of the foot, or anywhere else. One should bear in mind that, in mechanics, a heel-strap adhering to the ski at the centre of revolution acts like a rigid arm. The balance of the body is upset by sudden shocks which may react injuriously upon the foot, whenever there is a rigid connection brought into play, if only for one instant.
It is the business of the toe-strap to establish a connection (a close and immobile connection) between the foot and the ski, which it is the foot’s function to propel. To the contrary, to perform its office, the heel-strap requires no fixed points of vertical support. In a mechanically perfect binding, the foot of the runner would be free to revolve, as on a pivot, in the horizontal plane, spending thus forces of lateral origin, while the ski continued upon its course. As it is, a good runner surmounts disturbing, incidental forces (the ordinary cause of accidents arising from ski-structure) by passing them up along his body and neutralising their effect by shooting himself upwards, as if to fly.
When twigs of twisted cane were used they broke away under the strain. The long leather thong was stronger, but it froze, or imbibed water with too much alacrity.
A ski-binding is essentially composed of four parts:—
First: A ring, or toe-strap, in which to adjust the point of the foot, and which is the fulcrum.
Second: A heel-band, which, passing round the foot, presses its fore-part against the fulcrum, in the ring, or toe-strap.
Third: A fastener, either clamp, bolt, buckle with eye and prong, sole of appropriate length, lever, &c., wherewith to regulate and adjust the pressure of the heel-band upon the fulcrum.
Fourth: Side-supports, or cheeks, for the ball of the foot, generally placed on each side of the fulcrum.
It is under number three (clamps, buckles, and levers) that all fastenings are at fault. They would have to be self-adjusting, so far as quick adaptation to changing weather conditions and sudden running strains is necessary. But such cannot be automatically obtained yet. The best fasteners are approximate in their action. The worst are clumsy mechanical contrivances. Most, good or bad, link the heel-band with the ski blade. Some fasteners are placed on one or both cheeks.