Girard-Perragaux made a key-wound, high-grade pocket watch for the English market around 1860. One of the technical features of this timepiece is the escapement, which is what is called a detent escapement. The detent escapement was, as far as we know, invented by French horologist Pierre LeRoy in 1748, although the first practical version of the escapement was the pivoted detent escapement of John Arnold in 1775. Arnold’s contemporary in England, Thomas Earnshaw, was responsible for developing the version of the detent escapement that came to be most widely used. The basic layout of the spring detent escapement was shown in the 1896 edition of Britten’s The Watch and Clockmakers’ Handbook, Dictionary and Guide. The detent escapement came to be called a chronometer escapement, thanks to the use of the word as a designation for a precision watch containing a detent escapement. The very first person to use the word “chronometer” in reference to a watch with a chronometer escapement seems to have been none other than Arnold himself, who coined the term “pocket chronometer” in 1782. From that point forward, and for some time, “chronometer” primarily denoted (at least, in English language watch and clock-making) a precision timepiece with a detent escapement. As Fritz von Osterhausen points out, however, in Wristwatch Chronometers, “the main characteristic of a chronometer is its precision”, and as lever watches gradually achieved very high precision, the term came to mean, by the 20th century, any very accurate watch. Osterhausen writes: “In 1925, the Swiss Association for Chronometry defined a chronometer in the following way: ‘A chronometer is a watch which has received a certification from an astronomical observatory.’” Today, almost no one but a few diehard lovers of antiquated terminology still insist that “chronometer” should only be used to refer to a watch with a detent escapement (which is a good thing for Rolex and Omega and Breitling and a lot of other brands for whom a chronometer rating is a selling point). Origin of ‘chronometer’
Now, for many years, I have been asking other watch enthusiasts whether they know who invented the term. As the answer has generally been “no”, it has given me a chance to smugly repeat the conventional wisdom, as found in Rupert T Gould’s The Marine Chronometer: Its History and Development (and elsewhere), that it was apparently coined by an English clockmaker named Jeremy Thacker in a pamphlet on the longitude problem that was published in 1714. The funny thing is, information gets easier to find every day and in doing research for this story, I started to run across assertions that the pamphlet was a “probable satire” and that, in fact, there may never have been a Jeremy Thacker, horologist and pioneering longitudinarian, at all. Let us look at the evidence. In 1714, a pamphlet was published, with the author’s name given as Jeremy Thacker. Now, given the title of the pamphlet, it is interesting that the possibility of its being a satire did not occur to someone sooner. The pamphlet is called The longitudes examin’d: Beginning with a short epistle to the longitudinarians, and ending with the description of a smart, pretty machine of my own, which I am (almost) sure will do for the longitude, and procure me the twenty thousand pounds. That kind of language already sounds like someone is pulling your leg. Here’s a little background. The first Longitude Act, establishing the £20,000 prize, had been passed earlier that year and Thacker’s pamphlet was just one of many, many reactions. As you might expect, the enormous amount of money offered for a solution to the longitude problem brought a lot of cranks out of the woodwork in very short order, and Thacker takes to task several of the more egregious examples of improbable solutions to the longitude problem in his pamphlet. He also used the word “chronometer” for almost the first time it is known to have appeared in print in English. After going to considerable length to describe his ideas for a reliable sea clock, he writes: “In a Word, I am satisfy’d that my reader begins to think that the Phonometers, Pyrometers, Selenometers, Heliometers, Barometers, and all the Meters are not worthy to be compared with my Chronometer.” Everyone from Rupert T Gould to Dava Sobel (in her bestseller Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, which first made the general public aware of the longitude problem) seems to have taken at face value the notion that Thacker was a real person, and that his proposal was serious. However, in a 2011 book, Documenting Eighteenth Century Satire: Pope, Swift, Gay, and Arbuthnot in Historical Context, author Pat Rogers makes the claim that Thacker was the invention of a Dr John Arbuthnot. Arbuthnot was a physician and mathematician and, most significantly, he was a member of the Scriblerus Club — a group of satirists that included Alexander Pope and Jonathan Swift.
But you never know. The ancient Greeks had the word “chronograph”, although the term meant the keeping of historical records. The ancient Greek for a time-measuring instrument is “chronolabon”, literally something that “takes” the time. This word shows up around AD400 (in the writings of Proclus of Constantinople, if you are curious), so it is perfectly possible that “chronometer” in the sense of a time-measuring instrument, is a lot older than we can discover for now. In modern Greek, “chronometro” can mean either a timer specifically, like a stopwatch, or a chronometer in the sense of a precision timekeeper, but the word seems not to have occurred in classical literature. Despite Swift and the other Scriblerus members’ conviction that methods for finding longitude were about as intellectually respectable as proposals for perpetual motion machines, John Harrison was able to demonstrate a practical sea chronometer only a relatively short time after the 1714 Longitude Act. As a young man, Harrison had finished his first clock in 1713, and by 1761, his marine timekeeper H4 had made its proof-of-concept voyage to Jamaica, enabling the HMS Deptford to find its longitude with an error of only one nautical mile. And by then, of course, the escapement, which would come to be synonymous with the word “chronometer”, had already been invented by LeRoy. It is kind of fascinating to think, though, that the two earliest known uses of the word came from such different contexts. One was a serious text on the evidence for a divine hand in the structure of the universe. But the other, almost-first use of a word that became synonymous with precision timekeeping, and which represents a major marketing point for every brand that uses it today, was in what may have been a satire. — Bloomberg LP Originally published by Jack Forster on hodinkee.com This article appeared in Issue 790 (July 31) of The Edge Singapore.