Next message: Frank Reed: "Re: Can anyone tell me why my sextant has two sunshades?"
George H, you asked:
"If there were a few diehard old-school mariners clinging to older methods,
then indeed position-line navigation would not have become universal. Is that
all that he is implying?"
No, nothing so wishy-washy! <g>
As late as the 1930s, a substantial minority (maybe 25%??) of navigators
were still using straight, simple time sights and Noon Sun --no celestial lines
of position. At some earlier date, that proportion crossed the 50% "tipping
point". I don't know when that was (and it would be very tough to prove) but
I'm looking at 1900-1905 right now. That's sixty years after Sumner published.
I think there are plenty of reasons for this including issues of plotting
and charting, vessel speed, mathematical complexity, bias regarding algebraic
versus plotted solutions, and also, perhaps, an intangible sense that a
problem already solved did not need solved again (thou shalt not re-invent the
wheel --and yet we do).
And you wrote:
"It seems to me that one of the conditions pushing mariners to adopt Sumner
techniques was the climate. Mariners returning to anywhere in Northern Europe
had to find one of the narrow approach channels around the British Isles,
after an ocean passage. Our climate is such that the Sun may be only fleetingly
visible for days at a time. If and when it appeared, the sextant would be
brought out, whether it was noon or not. The chance was too precious to be
missed. There might be weeks at a time when no noon sights were possible at all."
Yes, I agree with that. Climatic differences might well explain variable
rates of adoption of celestial lines of position in different parts of the world.
By the way, somewhere in W.E. May's navigation history, there is a comment
about pre-war navigators (meaning pre-1940s) in the merchant marine dispensing
with position lines and "reverting to" time sights and Noon Sun. I don't
have a copy handy, but I think I'm remembering the phrasing right. I don't think
he's specific, but I assume he was talking about *British* navigators.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
