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    Re: Scrap paper with time sights c.1870
    From: Lars Bergman
    Date: 2013 Apr 4, 08:01 -0700

    Frank, yes I have enjoyed it!

    Looking back at my previous post, I've found two mistakes:

    First, I wrote that the chronometer was gaining during the first voyage, should have been losing.

    Second, I missed all observations on the "blue-4". Thus, the October voyage started at 31N 72W on October 22nd, but continued until October 31st, after passing through the Bahamas, south of Florida and ending off the Mississippi delta. In all this gives 41 time-sight reductions.


    In the October voyage, the chronometer is gaining. Between 26 and 28 October there is a large jump in the correction, presumably based on a terrestrial longitude observation when passing the Bahamas.

    Now, to the most interesting part: Blue-4-5 and blue-4-1 as well as blue-4-6 and blue-4-8 seems to be Sumner lines, in each case the same observation is reduced using two different latitudes. These are some of the latest observations when the vessel was off the low shores of the Mississippi delta. I believe Sumner published his work first in 1843 so it fits in time, although I don't believe his method was very common as early as 1855.

    Enclosed is an updated summary.

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