A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: How was GMT originally established ?
From: George Huxtable
Date: 2004 Jan 30, 11:33 +0000
From: George Huxtable
Date: 2004 Jan 30, 11:33 +0000
Bill Allen wrote- >I have tried to find the last article or book cited in your email, the >one from Rupert Gould and have not had much luck. I have found numerous >editions of books with titles that include words like "Enigmas," >"Curiosities," "Unexplained Facts" or "Oddities," and even one entitled >The Stargazer Talks, but not "The Marine Chronometer." > >Could this be a chapter in one of these other books? Otherwise, maybe >there are just no copies available through the online book searches I >have used. ==================== Response from George. It's a book on its own, not a chapter. Here are further details, in case they help. On the jacket of my 1978 reprint, its title is (the "the" is omitted here-) "Marine Chronometer its history and development. by Lieut-Commander Rupert T Gould, RN." On the title-page, it's given as "The Marine Chronometer". I don't think the presence or absence of the initial "the" would affect any book search. The reprint was published by The Holland Press Ltd., London, who reprinted it in 1960, 71, 73, 76, and 78 (and maybe later as well). The reprint is ISBN 0 900 470 17 8. The original book was published in 1923, don't know the publisher, presumably long before the days of ISBN. I should warn any prospective purchaser who happens to find one, that the Holland reprints, though hardback, were not well bound (edge-bound instead of folded in octaves) and some illustration pages are becoming detached on my copy, which has been well thumbed. I suggest that Bill Allen posts it as a "want" with Abebooks.com Rupert Gould was the man that got Harrison's four chronometers going again for the National Maritime Museum at Greenwich, so he knew what he was talking about. Harrison's No 1 is still kept going , and a wonderful sight it is to see it pulsing away in its glass case. Unlike most clocks and watches, everything is big enough so that you can get an idea what's going on, even though it's so incredibly complex. For any maritime visitor to London, it's a must. And the NMM is now free-of-charge again, I'm pleased to say. ====================== Fred Hebard said- >It thus appears that Harrison did not really invent the marine >chronometer so much as show that it was possible to build one. It >appears that the Frenchman Pierre Le Roy has as much claim as Harrison, >although Harrison's timepiece worked whereas I have heard no mention >that Le Roy's did. > >This differs from the view I obtained from Dana Sobel, which was that >later chronometers were copies of Harrison's. It also may explain in >part why it took so long for chronometers to come into general use. ===== From George- I think Fred has got it about right. Do not rely on Sobel for facts. She was making an entertaiing story about matters on which she was no expert. Harrison's story was rather a strange one, though. He developed a series of large clocks, all with slow and weighty contra-rotating balance wheels to null out the motion of the vessel, which showed that a precise marine clock was possible, and taught him the niceties of temperature compensation. Then he made (or more precisely had made for him) his H4, which was a complete departure from what had gone before, with a single quick-ticking balance wheel, which could override the accelerations of the ship mainly because of its faster action. He was brave enough to discard, at that late stage, much of his accumulated prejudices. The main prejudice he discarded was that an accurate clock had to be big, slow, and weighty, because all precise land-based observatory clocks had followed that pattern. But Harrison's H4 timepiece, copied by Kendall as K1, and carried by Cook, was also something of a dead-end, because it was so complex. The adopted design, developed along similar lines by the Swiss Berthoud, and by Arnold and Earnshaw in England, became the pattern for the mass-produced chronometers which continued with little change for the next 200 years (though early Arnolds were diastrously bad). They borrowed little from Harrison, except for the knowledge that the job could be done. Le Roy, in France, was in a rather different category (or Gould thinks so, anyway). He was very inventive, so his timekeepers differed considerably from each other. For example, some carried an alcohol-in-glass thermometer, attached to and forming part of the balance wheel, which displaced mercury to a different radius as the temperature changed, so changing the moment of inertia of the wheel. This was to compensate the oscillation time of the balance wheel and spring, for changes in temperature. However, I gather from Gould that for all his originality he did not found a production-line of intruments for mariners, as the others did. ================ Earlier, Patrick Stanistreet had said- >> Once Harrisons clocks were being manufactured and distributed >> to the fleet each clock would have to be set to some >> standard at least initially perhaps by Harrison or his >> family. =============== This is somewhat misleading, because Harrison's clocks never were "manufactured and distributed to the fleet" Even Kendall's K1, that went with Cook, included some changes from H4 that Kendall introduced. K2 and K3 didn't go as well as K1, and Kendall made no more. Clocks that went to the fleet were of different design, made by others, such as Arnold. I should point out that none of the stuff above is based on any knowledge or research of my own, but is based in reading others, mostly Gould. ================ I would like to comment further on thomas Schmidt's statement- >On the other hand, mean time is defined with respect to the Sun, >and an observation of the Sun directly supplies the correct time >(after application of the equation of time). To use a star as >a time indicator, you need to know its position, and its right >ascension can only be measured by timing its transit with respect >to mean time which again depends on the Sun. Once you have this >position, you are independent of the Sun, but any error in the >position will slightly affect your time measurement, and different >stars will have different errors and thus give slightly inconsistent >time readings. ============== Yes you can use the Sun, or various stars, to indicate the local time-of-day, if you have a transit instrument accurately set up to sight the meridian. But all Harrison had was an arbitrary ad hoc transit, between window and chimney. The time at which different stars crossed that transit was not simply related to their declination/ right ascension, as would have been the case if it was on the meridian. And the times of crossing of the Sun would vary through the year because of its changing declination (as well as equation of time). So the Sun was ruled out as a timer. All Harrison could rely on was the fact that each individual star always crossesd the chimney at intervals of exactly 1 sidereal day. And that was all he needed. He could cross-relate one star-crossing with another, which would become necessary as the seasons changed, by using his clock to interpolate between them, once he had got his rate right. =================== Anyone wondering why time-balls and time-guns always went at 1p.m. and not at noon, though they were sometimes referred to as the "noonday gun"? It was a concession to the navigators in port, because at and around noon itself, they were assumed to be busy observing the Sun. When I see or hear one, it always reminds me of the hilarious Noel Coward song, "Mad dogs and Englishmen (go out in the midday Sun)". One of the lines is- "In Hong Kong, they strike a gong. And no further work is done..." From the title, you can guess the next line. George. ================================================================ contact George Huxtable by email at email@example.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================