VERGE. In the limited sense the verge is the rod or spindle upon which the balance or foliot is mounted. It carries two 'flags' or pallets In the wider sense the word implies a watch with the verge or crown wheel escapement.

VERGE ESCAPEMENT. See Fig. VII and Pl. 129. Sometimes called the crown-wheel escapement, it was used in the earliest watches; its inventor is unknown. It consists of a crown wheel (the escape wheel), the arbor of which carries a pinion driven by the train. A vertical arbor (the verge) is at right angles to the crown wheel and has two pallets or 'flags' separated by a distance approximating to the diameter of the crown wheel and at an angle of approximately 100 degrees to each other. The verge carries at its upper end a balance and is pivoted at its two extremities. The teeth of the crown wheel act upon the pallets alternately and cause the balance to oscillate.

The eleven or thirteen teeth of the crown wheel are very approximately a sloping triangle in shape and the wheel itself somewhat resembles a medieval crown. A tooth of the crown wheel comes into contact with one pallet, thrusts upon it (gives it impulse) and imparts circular motion to the balance, which motion moves the pallet away from the tooth until this is free to slip past the pallet which has been pressing upon it. The crown wheel is momentarily free to advance, but almost immediately a tooth on the opposite side of the wheel comes into contact with the other pallet, the circular motion of the balance having brought it down into the path of the wheel. In order to free itself (escape) this tooth thrusts the second pallet out of its path, thus giving the balance an impulse in the opposite direction. The continued process results in the oscillatory movement of the balance and a tooth by tooth advancement of the crown escape wheel.

The verge is a recoil escapement. There is a supplementary arc of balance swing - i.e. the balance continues its gyration after it has been impulsed, and the teeth of the crown wheel are undercut to free the face of the pallet during the resulting recoil. The inclination of the teeth is about 30 degrees. Fig. VII and Pl. 129 show a verge escapement with balance spring.

 P1.129. Crown (escape) wheel, arbor and pinion. Balance, balance spring and verge. One flag (pallet) can be clearly seen on the verge.

VIRGULE ESCAPEMENT. See Pl. 130. Also known as the 'hook escapement', deriving both names from the part which receives impulse, this being somewhat like a comma in shape. Like the cylinder escapement (to which it has some similarity) it is a frictional rest escapement, usually credited to J. A. Lepaute, and it was used in France in the last quarter of the 18th century and during the early years of the 19th. This escapement appears also to have some resemblance to the patent taken out in 1695 by Edward Booth and William Houghton and in which Tompion seems to have been associated. The patent refers to a wheel with teeth 'made like tinterhooks' to 'move the balance', the pallets being 'circular, concave and convex'.

The virgule escape wheel has teeth standing up from the plane of the wheel. The teeth may be described as pins. These lock on the outside edge of the rounded part of the 'comma' or small cylinder and give impulse when entering and passing along the inner side of the downward curve of the 'comma'. The balance, therefore, receives impulse in one direction only, and not in both as occurs in the cylinder escapement. J. A. Lepine employed this escapement in conjunction with his bridged movement: the Lepine calibre (q.v.). The double virgule, invented by Beaumarchais, is exceedingly rare.