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The Encyclopedia of Horology

Component record · Escapement

Verge (Verge Escapement Assembly)

Verified

The earliest widely used mechanical escapement, comprising a crown-shaped escape wheel and a vertical staff (the verge) carrying two flag-shaped pallets set at roughly a right angle to each other.

What it does

Alternately locks and releases the crown wheel's teeth as the verge oscillates (driven by a foliot or, later, a balance), converting the going train's rotary drive into a regulated back-and-forth impulse.

How it works

The crown wheel's teeth project axially rather than radially; as it turns, a tooth pushes against one pallet on the verge, driving the verge (and the balance or foliot fixed to it) to rotate, until that pallet escapes the tooth and the opposite pallet, now presented on the other side of the wheel, catches the next tooth and is pushed the other way.

This continual give-and-push produces a very audible 'recoil', visibly kicking the crown wheel backward slightly at each impulse — a hallmark that distinguishes recoiling escapements such as the verge from later detached escapements.

Because the balance or foliot is never free of the escapement's influence (it is always either receiving impulse or transmitting recoil back to the train), verge timekeeping is comparatively poor and highly sensitive to variations in drive torque, which is why verge watches were almost always built with a fusee to even out mainspring pull.

Evolution

Superseded in quality work first by the cylinder and duplex escapements and then decisively by the lever escapement through the eighteenth and nineteenth centuries, though verge movements remained common in cheap watches and some regional clockmaking traditions well into the 1800s.

Known variations

  • Verge with foliot (earliest clocks, no balance spring)
  • Verge with balance and balance spring (from the later seventeenth century)
  • Verge fusee pocket watch, the commonest surviving configuration

Identification for collectors

  • A crown-shaped escape wheel with axial teeth, quite unlike the radial teeth of a lever or cylinder escape wheel
  • Visible recoil (slight backward kick) of the escape wheel at each beat when observed closely
  • Almost always paired with a fusee in watches, and with a foliot or an unsprung/early sprung balance

Common failure modes

  • Heavy wear at the pallet faces and crown-wheel teeth from the sliding, high-friction action inherent to the design
  • Poor timekeeping and high sensitivity to position, considered inherent limitations rather than repairable faults
  • Verge and potence pivot wear, since the verge staff bears significant side-thrust in use

Related photographs

Lindquist Fusee Pocket Watch Movement
Lindquist Fusee Pocket Watch Movement — Gervald Frykman User:G N Frykman, Public domain. Wikimedia Commons file page
Spindeluhr fusee verge watch fabris 02
Spindeluhr fusee verge watch fabris 02 — Sergio Fabris, CC BY-SA 4.0. Wikimedia Commons file page

No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.

Sources & references

  1. Britten, F. J., Old Clocks and Watches and Their Makers
  2. Daniels, G., Watchmaking

Where sources disagree, the disagreement is stated rather than resolved silently.