Expertise

Mechanical watches are constructed by combining numerous distinct sub-assemblies. The ‘gear train’, sometimes referred to as the ‘wheel train’, is one of these sub-assemblies. Its function is to transfer energy from the mainspring assembly to the escapement mechanism. During this transfer, the force supplied by the spring is reduced to a fraction. Via the minute-wheel, the gear train also drives the display mechanism. This includes components such as the intermediate-wheel the cannon-pinion, the hour-wheel and also the centre-wheel-pinion. These components hold and move the hands of the watch. The gear train in a normal wrist or pocket watch includes components with names such as the minute-wheel, the centre-wheel, the second-wheel and the escapement-wheel with their various driving gears. In this constellation, the escapement-wheel is rather special. Whereas its driving mechanism makes it technically part of the gear train, its central role in the escapement mechanism makes it part of this assembly too.

See Poinçon de Genève.

See Côtes de Genève.

GMT stands for Greenwich Mean Time. The Earth is divided into 24 time zones with the start of the first time zone, or ‘zero meridian’, running from North to South through the town of Greenwich in England. The actual time in any place in the world is always made relative to GMT. For Instance: New York is GMT –7 hours, Sidney is GMT +8 hours and Bangkok is GMT +5 hours. GMT is also WET or West European Time.

Gold is an especially valuable metal. Its specific gravity of 19.3 makes it one of the heaviest metals in the world. Gold has a natural yellow colour, which does not change when exposed to air. However, the colour of gold can be varied by mixing it with various alloys, for instance; adding silver and nickel creates white gold while adding copper creates red gold. Gold has always been prized as a jewellery metal and it has been used for centuries to make watch housings. Gold is a soft metal and it is very easy to form. Due to its malleability, it can be rolled out into very thin sheets from which watch components (for instance; watch plates) can be made.

This is a striking mechanism that automatically chimes the hours and quarter hours ‘en passant’ (or as it passes them). A ‘Petit Sonnerie’, in contrast, strikes only the hours.

In 1582, Pope Gregory XIII developed the Gregorian Calendar, which is named after him. This calendar was intended to replace the Julian Calendar which had been in use since the reign of the Roman Emperor Julius Caesar. It was, however, only introduced by imperial order in 1776. The Gregorian Calendar divides the year into 365 days, 5 hours, 48 minutes and 46 Seconds. The inaccuracy of more than 5 hours per year is dealt with by adding an extra day in February every 4 years – known as a ‘leap’ year. Unfortunately this solution still leaves some inaccuracy. This has been dealt with by ordaining that each leap year that can be divided by 100 will have the normal 365 days (i.e. will not be a leap year; 2100 will be such a year). Even after this correction there is a small amount of inaccuracy remaining. To deal with this, each 400 years, even if the year is divisible by 100, the month of February will indeed have 29 days. (This last happened in the year 2000.)