The words CHRONOGRAPH and CHRONOMETER are used. CHRONO from the Greek KHRONOS meaning ‘’time’’.
An early attempt to accurately measure elapsed time – for instance a horse galloping over a furlong – was solved by adapting the early large pocket watches that had hinged glass covers. A small nib with ink reservoir was added to the minute hand. Pressing this nib against the dial at the start of timing and releasing at the end gave an ink trace, the length of which gave the elapsed time. In other words a time graph or CHRONOGRAPH.
Nowadays CHRONOGRAPH implies a time of day watch that also has the ability to measure elapsed time or if you prefer a watch with a built-in stopwatch. Stop watches count up so, to distinguish this facility from a count down ability, we refer to count down timers, or just ‘’timer’’.
CHRONOMETER on the other hand implies a very high standard of time keeping accuracy for Navigational purposes. To the best of anyone’s knowledge the word was first used half in jest by Jeremy Thacker in 1714 who was mocking the many impractical suggestions for solving the longitude problem which included canon firing ships positioned across oceans, compass needles heated by fire, wounded dogs to yelp at noon in sympathy with a treated dog left ashore, the moon’s motion, the sun’s elevation and so on. Thacker had developed a new clock working in a vacuum chamber which was an undoubted advance and in extolling its virtues wrote: “the PHONOMETERS, PYROMETERS, SELONOMETERS, HELIOMETERS and all the METERS are not worthy to be compared with my CHRONOMETER”
The word caught on and became the description of a timepiece accurate enough to measure longitude at sea. This was originally set by the Longitude Act of 1714 as three seconds in 24 hours over six weeks to win the £20,000 prize on offer. It also at one point came to mean any movement that would produce this degree of accuracy. Various observatories around the world have seen fit to set their own somewhat laxer standards for the purpose of issuing Certificates of Timekeeping but we consider the original historical yardstick should remain the minimum standard of time keeping for this much prized accolade.
As is well known the first person to produce a chronometer worthy of the name and the prize was the genius John Harrison with his famous series of timekeepers, H1,2,3 and 4, produced between 1737 and 1760.
The introduction of pulsing quartz to replace hairsprings and balance wheels in 1985 allowed a standard of accuracy that John Harrison could only dream of; together with great reliability and robustness at very affordable prices.