The Verge escapement, as applied to Watches, will be seen annexed, A, part of the balance; b, the verge body; C, C, the pallets; D, the escape-wheel; E, escape-wheel pinion. The verge or arbor B of the balance has two pallets, C, C, which stand out at right angles, so as to be acted on alternately by the sloping teeth in the opposite sides of the crown or escapement-wheel, C.
The Horizontal escapement, on the following page, so called because of the escape-wheel acting horizontally to the axis of the balance. This invention was perfected by Graham, after the death of the inventor, his master and friend, Thomas Tompion. a, the escape-wheel, having pins or stems rising from it, on the tops of which are teeth of a wedgelike form, of such a length as to permit little freedom within and without the cylinder b, which is firmly fixed to the balance c. Although b is one piece, the two edges of the hollow part serve as distinct pallets, inasmuch as they receive alternately, during each vibration of the balance, an impulse from the curved outer edge of each tooth in succession; and as the wedge-shaped tooth passes from the pallet, the coming tooth falls on to the circular part of the cylinder, and there remains until the return of the balance, when that tooth which had previously rested on the circular portion of the cylinder, comes upon the edge or pallet, gives impulsion to the balance c, and falls upon the concave portion of the cylinder, and there remains until the balance again returns, when another impulse takes place, and so on in succession. Watches having the cylinder escapement were not known in France till the year 1728, when Julien le Roy obtained one of them from Graham.
Horizontal Escapement.
Duplex Escapement.
The Duplex escapement is of a very peculiar construction, and nearly approaches the chronometer; it is probable that it was originally invented by Dr Hooke, although, as we now have it, it came from the hands of Tyrer. It is seen in our illustration. A, the escape-wheel; B, the escape-wheel teeth; C, the balance; D, the pallet of impulse; E, the ruby roller; F, a notch in ditto: 1, 2, 3, cogs or upright teeth on the rim of the escape-wheel. The balance is supposed to be turning downwards towards the right, the tooth of the escape-wheel just resting against the ruby roller. When this (which is called the return) vibration is complete, the balance, by the strength of the hair spring, is carried in the opposite direction, and as the notch F passes the tooth of the escape-wheel, this latter is enabled to pass the roller, and the upright tooth or cog falls upon the pallet D, and thus gives impulse to the balance. The next straight tooth of the escape-wheel is now resting against the roller e, and the same operation again takes place. This escapement is much superior to the horizontal, and is almost independent of oil. It can carry a balance of much greater weight, and when well made performs admirably. Duplex watches, however, should never be selected by persons who are accustomed to ride on
