NavList:

   

Reply

I certainly so not question the evidence produced by actual voyage log
books, but do wish to remind all hands of Thomas Arnold's work both in
publishing and in conducting a school intended to educate the mariner in
working Lunar Distances. As I have previously noted on this List,
Bowditch was not alone in the advocacy of Lunars in the USA - Arnold,
certainly a commercial vessel navigator, states having utilized them over
a 40-year period as Master of American vessels, and in the 1820s wrote
rather prolifically on the subject and actually operated a school at
Philadelphia.

It would be of interest to consider whether all navigation calculations
actually done aboard any particular vessel, aside from a notation of
position, was actually spread out on the pages of the log book, as
opposed to being calculated on scraps of paper or in a separate workbook
which remained the possession of the individual - of course it involves
an entirely different era, but I still retain volumes of navigation work,
of which only the resultant position ever found its way into the logbook.
As they say, however ..."Different ships, different longsplices".

Henry

On Sun, 5 Dec 2004 16:06:59 EST Frank Reed  writes:
> From the 18th and 19th century logbooks I've studied (only a sample
> of the
> thousands out there), I've noticed a pattern. Lunars (lunar distance
> sights)
> were never a primary method of navigation for American commercial
> vessels.
> There  was no "lunars era" comparable to the "chronometer era".
> Rather the primary
>  method of determining longitude until the 1830s or so was dead
> reckoning, as
> it  had been for centuries. Around 1830, the primary method began to
> switch
> over to  chronometers. During the early period of lunars, from
> c.1770 to
> c.1830, lunars  were used as an occasional check on the dead
> reckoning. In their
> logbooks,  navigators only occasionally updated their dead reckoning
> with results
> from  their lunars observations. Rather, they continued their dead
> reckoning
> until  they were able to take a new departure from a point of land
> with
> results of  lunars listed marginally. The "mindset" was centered on
> the dead
> reckoning.  After c.1830 (and it is a decades long process of
> transition), the
> primary  longitude listed in the logbooks become "long by chrono"
> with occasional
> checks  by lunars.
>
> For an example of a late holdover, take a look at the logbook of the
> bark
> "Mary & Louisa" from 1858 in the collection of the library at Mystic
> Seaport
> (mysticseaport.org). The navigator on this voyage from the northeast
> US to
> Shanghai uses dead reckoning as his primary longitude and for him
> the  chronometer
> longitude is only a sanity check, listed once in a rare while (no
> lunars
> either).
>
> I think I ought to risk stating the obvious here. Every navigator
> works in a
> unique manner. Many navigators in the 19th century never used lunars
>  at all
> --except "in the classroom". Some others, unusual navigators,
> apparently  did
> treat lunars as their primary method of finding longitude. But the
> only case
> I'm aware of personally is Nathaniel Bowditch himself. Additionally,
> I should
> note that the comments above refer specifically to "American
> commercial
> vessels".
>
> Any thoughts?
>
> Frank R
> [  ] Mystic, Connecticut
> [X] Chicago, Illinois

   

Reply