Whistles and similarly high sounds carry very well over broken terrain. This is the principle behind silbo (a whistle-based language from the Canary Islands, which is being preserved and regaining strength thanks to the efforts of local culture-preservation groups) and yodels (Basque irrintzis, for example, are a yodel-based language, although I understand that unlike silbo these are almost lost; nowadays if you hear an irrintzi it’s more likely to be a show of good lungs than a code for “anybody lost a blackface sheep with a red mark on the left foreleg?”).
Reading this, I wondered how much the speed of sound would affect this sort of thing. Looks like it would take a sound wave about 25 seconds to travel five miles, which isn’t too bad in terms of clock accuracy really.
Good post, Muffin.
For those who really want to get into this sort of thing, there are several good histories of time that cover the subject in massive (and to be honest, ofttimes boring) detail.
There also the bizarro Time Lord: Sir Sandford Fleming and the Creation of Standard Time, by Clark Blaise, a book as eccentric as its title subject.
Western Union used to have a popular telegraph based time service that would reset clocks to the correct time every day. There were many clocks that were designed to be used with this service.
http://www.telegraph-office.com/pages/time.html
I’ve seen many clocks in public schools that use a similar system to keep all the clocks synchronized. They all get a reset pulse once per day.
(in reference to due south vs highest point in the sky)
[quote=“Freddy_the_Pig, post:19, topic:470774”]
Yes, they are. Those two definitions are the same.
[QUOTE]
Well, Due North in the southern hemisphere, and north / south / overhead in the tropics (depending on the season), and the sun is always due south at the north pole (and due north at the south pole)
Brian
When John Harrison was developing the chronometer for navigation purposes he used celestial movements to verify accuracy.
Knowing what time it is right this very second is a pretty recent obsession. We’d all do better to follow the Corpus Clock, which sometimes appears to speed up or slow down or even run backwards, is accurate only once every five minutes, and is topped by the Chronophage, the hideous Eater of Time.
(seriously, coolest clock ever. You gotta see the video to appreciate how awesome it is.)
obsession with time goes back to the chronograph which was needed for navigation.
The video is pretty neat and it dawned on me that the grasshopper escapement was actually built like a grasshopper just before it was pointed out.
I haven’t seen anybody upthread mention the factory whistles that long regulated the lives of many industrial towns. Nor the ship’s bell that used to call the watch on those little communities at sea (a whole other meaning for “synchronize watches”).
I don’t know the full story behind either of these institutions, but I think they deserve a mention in this thread. Details, anyone?
It’s about 19th century London rather than the sort of situation the OP has in mind, but David Rooney at the National Maritime Museum has just published Ruth Belville: The Greenwich Time Lady about the family who ran a service synchronising clocks in the city with the Royal Observatory by the simple expedient of someone coming round once a week with a watch that had been freshly checked against the clocks there. This was in competition with the telegraphic services.
He talks about the book in this blog post.
They did that where I grew up, in the not-so-small city of Schenectady, NY.
Where I live now (outside Boston MA) a church about a mile away tolls the hours and also one-gong for the half-hour (although lying there at night it’s hard to tell if it’s 1AM or just some half-hour)
I my hometown (just outside Boston), the fire whistle was blown at 9AM and 9PM.
It’s very accurate, but of limited use. Aside from only being available at night, the precision required for the observations make it impossible to use on a ship at sea.
I think you misunderstand what I said. He used astronomy to verify his work on chronometers, not on ships. I’ve never heard it used to adjust town clocks but it would have been available technology at the time.
I think the U.S. Naval Observatory had special telescopes for measuring the time at which selected stars crossed the zenith. This was a way to compare local clocks against the “celestial clock”. The USNO was a source of time for the Washington area, and later, the USA.