RARE LARGE OIL CLOCK, SAXONY, LATE 18th OR VERY EARLY 19th CENTURY in pewter with bowl-shaped foot, ringed truncated conical shaft, and hinged flap burner, topped by a cylindrical glass bulb in ribbed blown glass, sheathed with an hour ribbon graduated in Roman numerals. Thumb rest handle Quality mark in cursive letters: F.Z (for Fein Zinn) (Complete with its iron wick holder; the screwing of the bulb to the shaft has worn, however, and is compensated for by a textile gasket). A RARE LARGE OIL CLOCK, SAXONY, LATE 18TH OR EARLY 19TH CENTURY 38,50 CM - 15,2 IN. How it works: the oil level falls as it burns and indicates the time on the graduated hour ribbon. It is important to distinguish between pilot lights and clock lamps. The former have an inverted pyriform bulb that is therefore incapable of providing a linear relationship between combustion and its reading on the time ribbon, while the latter have a cylindrical bulb that alone can satisfy this constant relationship.