Deadbeat (independent) seconds — Unsigned pocket watch, dead independent seconds date, Circa 1890 — Unsigned pocket watch, dead independent seconds date, Circa 1890 — Antiquorum auction archive, Geneva · © Antiquorum Genève SA — permission required · source (opens another website in a new tab)

Complication

Deadbeat (independent) seconds

Also known as: Seconde morte · Seconde foudroyante (related) · Springende Sekunde

How it works

The seconds hand advances in whole one-second jumps rather than sweeping. In 'independent' seconds it is driven by its own train and released once per second by a star or flirt controlled from the going train.

Why it was invented

Precise timing of seconds for doctors, astronomers and engineers — the second can be read exactly, as with a pendulum regulator.

Invented: 1776
Credited to: Jean-Moïse Pouzait (independent seconds)
Historical period: Precision & Scientific Horology

Experiment in the Simulation Lab →

History and development

Geneva watchmaker Jean-Moïse Pouzait made independent-seconds watches in 1776. 'Seconde foudroyante' (a hand turning once per second in fractions) and deadbeat seconds were popular in 19th-century Swiss pocket watches for timing.

A balance-wheel watch normally beats five or six times a second, so its seconds hand advances in small steps that look like a sweep. A seconds hand that jumps once a second therefore needs extra mechanism. In the classic 'independent seconds' watch a separate barrel and train drive the seconds hand, and a pin or flirt on the going train releases it once a second; in other designs a spring-loaded star on the seconds wheel stores a little energy and releases it in one jump. Pendulum regulators show 'dead' seconds naturally, because a seconds pendulum releases the escape wheel once a second.

Jumping seconds were valued in the nineteenth century by doctors taking a pulse and by anyone needing to read whole seconds at a glance, and some watches combined independent seconds with a stop slide, as an early form of timer. Quartz watches later made a once-a-second jump commonplace, but in mechanical watches it remains a rare, demanding complication; Jaeger-LeCoultre's Geophysic True Second of 2015 is one modern example.

How to recognise it

A seconds hand that jumps once a second, sometimes with a slide to stop it; independent-seconds watches have a second barrel and train.
Dials may be marked 'seconde morte' or 'independent seconds'.