NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Cable Time
From: Fred Hebard
Date: 2003 Mar 23, 22:28 -0500
From: Fred Hebard
Date: 2003 Mar 23, 22:28 -0500
I apologize if I'm repeating myself. But it seems to me there is a circular argument going on here. The navigators in the story very clearly were determining the error in their chronometers by land observations of sun or stars. There would be no need to do so if accurate time could be transmitted by cable. So one concludes that accurate time could not be transmitted by cable, or was not transmitted very often. (To do so, one would need to establish accurate time at the transmitting station. If that station were located near the shore, and relayed signals from Paris or London by land-borne telegraph, then I expect that accurate signals could not be propagated to the station by land-borne telegraph, due to the time delays introduced by relays along the way). It would seem to me to be much easier to determine time at the transmitting station by observing the moons of Jupiter or some such, in place. This also could be done at each cable station to determine longitude accurately. Once the longitude of a station were known, one could determine the error of one's chronometers as described. As George Huxtable describes, simple triangulation from the level spot to the benchmark spot could determine the location of the level spot, if the location of the level spot differed from that of the benchmark spot, which it might not.