Glossary · Mechanism
Fourth wheel
The going-train wheel that typically carries the seconds hand in a standard watch layout.
Explanation
The fourth wheel is the going-train wheel turning once per minute, whose extended pivot (seconds bit) carries the seconds hand in most layouts. It drives the escape wheel. In movements with centre seconds, an added wheel instead brings the seconds to the middle of the dial.
In the object catalogue
Catalogued objects whose own source record mentions “Fourth wheel”. The quoted line shows where; it is the seller’s or museum’s wording, not independent verification.
Pocket watch
I.A. & N.C. Keyless Half Hunting Case Karrusel Pocket Watch
“This half hunting case keyless pocket watch is attributed to I.A. & N.C., London, circa 1900. Housed in an 18K gold case, the watch features a 52 1/2 minute Bonniksen karrusel r…”
Pocket watch
H. GrandJean et Cie. Perpetual Calendar Pocket Watch
“This astronomical pocket watch, attributed to H. GrandJean et Cie. of Locle and London, dates to approximately 1870. The 53 mm timepiece is housed in an 18K gold four-body case …”
Movement
Movement of a gentleman's watch
“Visible central wheel, third wheel, and fourth wheel assemblies”