[LMB] OT: Oxymoronic "AM/PM"
pgranzeau at cox.net
Sun Aug 30 17:37:20 BST 2009
At 02:17 AM 8/30/2009, baur wrote:
>question: what system did US railroads use in late 1800-reds, early
The telegraph. Specifically, railroads used telegraphs almost from the beginning, independent of commercial telegraph companies.
For that matter, local clocks could be synchronized easily enough: just observe the time of local noon (the point at which the sun is directly south of the observation location) and apply a correction for latitude or longitude.
For example: I am one degree 30 seconds west of the meridian which is used for eastern time in the US. Thus, if I observe local noon, I know that time is actually six minutes after noon EST (an hour is 15 degrees, thus one degree is 4 minutes, and 30 seconds is two minutes).
Every important member of a railroad crew carried an approved timepiece. I believe their accuracy was supposed to be within 30 seconds a day (they thus needed to be reset and rewound daily), which is pretty good accuracy for a watch movement. Chronometer movements were supposedly accurate to 30 seconds a month, but a chronometer wasn't carried around in a working man's pocket, either.
37º 04' 26" N 76º 30' 08" W
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