NavList:

   

Reply

I wrote in my original post in this  thread:
"The CWM was already 56 years old on this voyage, and whaling was a  minor
business in the 1890s, so maybe it's not surprising that there's no  "rocket
science" in this navigation. Nonetheless, this very simple celestial was  good
enough to cross the Pacific from California to Micronesia and then on to  Japan."

And in a later message I wrote:
"That's how it was done for  decades on ships at sea even as late
the 1940s. With all the talk recently  on Sumner's method, I think it's worth
remembering that Sumner's lines were  considered a somewhat exotic technique,
one that might never be used in  months at sea. Celestial lines of position
didn't catch on universally until  almost a century after Sumner published.
And
why that was the case is still  a fascinating question... "

George H, you replied:
"To me, that's one  of those sweeping statements, that cries out for a bit of
backup evidence. There  is much evidence to the contrary."

I would love to see some!

Evidence in this business can be a tricky thing. For example, if you  open a
copy of Bowditch from about 1850 to 1880, you might think that "lunars"  were
an important thing, since many pages are devoted to them, while in reality,
they seem to have gone nearly extinct by about 1855. Meanwhile, if you open a
Bowditch from the same period and look for Sumner's method, you'll find only a
 half-page treatment. It would be equally unwise to treat this as evidence
regarding Sumner's method. Of course, given the popularity of Bowditch's
Navigator, it surely didn't help. I'm not saying that you can never use the
navigation textbooks as evidence of actual practice, but that evidence has to be
interpreted carefully.

Logbooks, navigational notebooks, oral histories  (for the later period),
those are the sorts of things that we can rely on as  evidence of navigational
practice.

And you also wrote:
"In his  "Wrinkles in practical navigation" (1881), Lecky, a practical
navigator if ever  there was one, and no academic, states that his chapters XI, on
Sumner Lines,  and XII, on Double Altitudes, are the most important in the
book."

Yes,  and at this date, forty years after Sumner's publication, Lecky still
has to  explain this AFTER detailing longitude by time sights. He's "selling"
Sumner's  approach as if it is something unusual. And why is he doing this?
Because, as he  puts it, this will help the navigator to "understand the
principle of the  problem". He further notes that "it is not always convenient to draw
Sumner  lines on a chart" [imho, this is a BIG factor] and suggests that one
should work  the problem by calculation rather than plotting. This calculation
is, as Lecky  puts it, "a formidable affair, and the rules at the finish are
so complicated as  to scare most ordinary seafaring men."

George, you added:
"He tells us  that within a year of Sumner's publication, an order was given
to supply a copy  to every ship in the US Navy!"

That's actually a quotation from the  preface of one edition of Sumner's
booklet (it was from a letter written by the  famous M.F. Maury). What does it
tell us? Well, it tells us that Maury ordered,  or promised to order, a lot of
books! It also tells us that Sumner's conception  of navigation received wide
"critical acclaim" from experts (and it certainly  did). It tells us little
about actual practice at sea.

And you  concluded:
"So I wonder whether that statement is based on a biased sample of
navigationally backward or ultra-conservative mariners; such as, perhaps,  American
whaling vessels. "

Certainly the SPECIFIC case the Charles W.  Morgan in 1896-97 should be
interpreted with that in mind. That's what I said in  my original post on the topic
(!). There were definitely navigators who used  Sumner lines in the late 19th
century, but they seem to have been rather  exceptional. And there were still
thousands of navigators even in the 1930s  doing nothing but Noon Sun and
morning/afternoon time sights of the Sun even  forty years after that voyage.

I have not examined even a small fraction  of the logbooks in the vast
collection at Mystic Seaport, but so far I have not  found a single example of
Sumner lines, Sumner line calculations, or even  references to the technique in the
19th century, outside of navigation  textbooks. Don Treworgy encountered ONE
reference to a Sumner line in a logbook  from the 1880s in the collection. The
navigator in question, Charles H.  Townshend, was famously experimental. For
example, he shot Jupiter in daylight  as a challenge. He mentions, just once,
that he "tried Sumner's method. Seems to  work." (or words close to that).

I'll mention here one specific problem  with Sumner's method. He explicitly
refers to Mercator's projection. This is  un-necessary. If he had simply
described a method for plotting on a plain sheet  of paper, the method might have
been seen as much more practical by navigators.  In fact, for what it's worth,
in the 1903 revision of Bowditch a rather long  explanation was inserted on
this very point.

The transition to celestial  lines of position as the unversal standard for
celestial navigation was very  slow, and the reasons are not entirely trivial.
To avoid potential mis-reading,  I am not suggesting that Sumner lines were
never used. I still like my earlier  phrasing: Sumner's method was considered a
"somewhat exotic  technique".

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars

   

Reply