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Bill Morris wrote

"On the front cover of John Thomson's biography of Frank Worsley
"Shackleton"s Captain", there is a painting showing Worsley taking a sight
with a ladder- frame sextant. Can you confirm that this is a correct
representation?"

To see what Bill is talking about here, you can go to amazon.com, under
"books" enter "shackleton's captain", and you will see a thumbnail picture
of the cover. This you can enlarge, to see about as much detail as there is
in the cover itself.

There's nothing that I could find, within the book, to acknowledge who made
that picture, but it appears that someone has at least gone to the trouble
of picturing an instrument of the right era. From the angling of the
fine-adjust knob, it looks to me like a clamp-on shoe type of Vernier, not
an endless-tangent model.

I can echo Bill's comment, about reading a Vernier sextant to within 10
arc-seconds-

"Even then, for me there is often uncertainty as to which of two or three
pairs of graduations line up, despite being  aided by a stero microscope at
X 15 power." I haven't had such optical horse-power at hand, but have
exactly the same problems, using the magnifier that's fitted to my own
Vernier sextant. It seems to be nearing the limit of perception. How
mariners managed to read such an instrument at night, in the dim glow of a
cabin lamp or a candle, quite defeats me.

=========================

Brad had some interesting words to say about his recent acquisition: indeed,
something to take a pride in. It may well correspond with Worsley's
description of the Heath instrument that he used on the Caird, which had
previously been presented to Hudson. But why, I wonder, did Worsley find it
more convenient for use on the boat than his own?

Brad wrote- "I can see why Worsley chose this sextant, it has every feature
you could ever dream of."
and ended- "At this point, you have to ask yourself if Worsley chose poorly.
Given the feature set and the fact that the expedition would have obtained
the greatest accuracy possible (zero point zero error) then this sextant is
an obvious choice."

For Worsley's task in hand, none of that "feature set", range of optics,
high accuracy, were in any way relevant. Indeed, for that job, of snatching
a rough altitiude from a small craft in a big sea, he might just as well
have removed the telescope altogether.

==========================

There's an comment from Worsley about his chronometer, for which he only
managed to get a rating from a glimpse of the Sun on their very last morning
on Elephant Island. He wrote- "This English chronometer, an excellent one of
Smith's, was the sole survivor, in good going order, of the tweny-four with
which we set out in the Endurance."

Twentyfour!! I suppose than not all would be the gimballed instruments in
mahogany boxes that first come to mind. Many would be pocket chronometers
for the intended sledge journeys, which would be required to return to base
from an expedition to the pole.


contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.


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