WHEEL, BREAKING ON THE, a very barbarous mode of inflicting the punishment of death, formerly in use in France and Germany, where the criminal was placed ou a carriage-wheel, with his arms and legs extended along the spokes, and the wheel being turned round, the executioner fractured his limbs by successive blows with an iron bar, which were repeated till death ensued. There was considerable variety in the mode in which this punishment was inflicted, at different times and in different places. By way of terminating sooner the sufferings of the victim, the executioner was sometimes per mitted to deal two or three severe blows on the chest or stomach, known as coups de grdce; and occasionally, in France at least, the sentence contained a provision that the criminal was to be strangled after the first or second blow. Mercy of this kind was, however, not always allowed to be shown to the victims of the wheel; when Patkul, the envoy of Peter the great, was put to death on the wheel by order of Charles XII. of Sweden, it is said that the officer in command of the guard was cashiered by the Swedish king in consequence of having allowed the head to be struck off before life was extinct in the mangled limbs. The punishment of the wheel was abolished in France at the Revolution; in Germany, it has been occasionally inflicted during the present century, on persons convicted of treason and parricide.
The arrangement for conveying motion from one axis to another by means of toothed-wheels, is familiar to every one; it has been in use since the days of Archimedes, and was in use, probably, for many centuries before; but it is only in modern times that the action of such wheels has been critically examined and understood. To a superficial observer, the action appears to be extremely simple; a tooth of the driver pushes against a tooth of the driven wheel, thereby causing that wheel to turn round; and, since by this turning the teeth mutt become disengaged, it is requisite that, before one tooth let go, a second tooth of the driver be ready to take hold of another tooth of the driven wheel. For this purpose, it is enough that the distances between the teeth on the two wheels be alike; in other words, that the diameters be proportioned to the number of the teeth.
When two unequal wheels act upon each other, the smaller one turns faster than the larger. Thus, if a wheel with 60 teeth work into one of 20, the latter will turn 3 times as quickly as the former; and it is on this principle that time trains of clock-work are arranged. For exainple, the of a common house-clock' may have 180 teeth, and may drive a smaller wheel, or pinion as it is called; of 15 leaves, and in this case, if the great-wheel turn once in 12 hours, the pinon must turn once in every hour; the axis of this phion carries the minute-hand. On the same axis the is fixed which may have, say, 96 teeth, and may drive a pinion of 12 leaves. This pinon, then, must turn 8 times per hour, or once in 7} minutes, Ou the same axis with this last-mentioned pinion there is fixed the third wheel, having, perhaps, 75 teeth, and this drives a pinion of 10 leaves, which, turning 7} times as fast, must make one turn per minute. On the axis of this last pinion the is fixed, This escape-wheel has 30 teeth, each tooth acting twice upon the pendulum, thus making 60 beats per minute. In such a case as this, there is no difficulty in arranging the numbers of the teeth, and these may be varied in many ways, provided the proper proportions be kept. But in other cases, a considerable amount of skill, and often a great deal of labor, is required for the dis covery of the proper numbers. Thus, if it be wished to indicate tne moon's age on the dial of a clock, we must have index turning once in the time between new moon and new moon. This time, which astronomers call a lunation, averages 29 days, 12 hours, 44 minutes, and nearly 3 seconds (2.853), and it is by no means an easy matter to rind out what number of teeth will produce this motion. Time mouth-wheel would need to turn rather more than 59 times as slowly as the great-wheel of the clock; and if the mean lunation had been 291 days, without the odd 44 minutes, the thing could have been managed by making a pinion of 8 teeth lead a wheel of 59 teeth, on the axis of which another pinion, say of 10 teeth is fixed, and made to work a wheel of 50 teeth.