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Gentlemen

I have examined the book cover and yes, that appears to be the
appropriate ladder sextant.  Since it is a painting (and clearly not a
photograph, hehehe, like they brought a camera) then we can permit the
artist some degree of leniency with regards to the angle of the endless
tangent angle adjustment knob.  I will check tonight to see if my knob
is at the same angle.

In regards to reading the vernier, there is a small sheet of translucent
glass, mounted perpendicularly to the arc.  Its purpose is to diffuse
the light over the arc where you are attempting to read it.  You hold
the light parallel to the arc, not pointed at the arc, rather at the
back of the translucent glass.  I use a small red LED but I do agree
with George's point, it is a little tough to read.  Once you get used to
it, it isn't so bad.  Am I reading it to 10"?  I doubt it, but I do take
extra-ordinary care to assess the reading.  I use the scintillation of
the light on the graduations to make the final call and yes, it is
always a judgment call.  Thanks Bill for the assessment of wear and
eccentricity.

George makes an excellent point about which sextant.  I foolishly
assumed he picked the best one available.  Maybe it was the only one
available!  There was discussion about how overloaded the boats were
when they journeyed from the ice to Elephant Island.  Perhaps they
ditched the other sextants, retaining the best one?  The logbook does
not carry down to seconds when the reduction is performed, only to the
nearest minute of degrees. So clearly, he didn't use the terrific
accuracy inherent in the sextant.  

There are two chronometers I have found images of which purport to be
the ones used by Worsley.  One is the box gimbaled type, while the other
is a pocket watch type.  I can lend no clarity which one is correct, in
particular which one was used on the journey.

The log book has a note in the margin which states "Lat proved to be
correct within about 2m.  Long ditto but Chron was much slower than I
had allowed which made us about 20 miles of distance further xxxx than
obs showed".  Try as I might, I could not read what word he has for
xxxx, however, if the chronometer was slower than expected; then NavList
can tell me, was that east or west? The chronometer rate determined at
Elephant Island was 5 seconds slow per day.  

I have been contacted by Canterbury Museum.  The missing page of the log
is on its way!  Honorable folks. The page missing clearly contains 4
May, 5 May and 6 May, so some more clarity will be had about the
decision making process Worsley entertained, when it arrives.

Best Regards
Brad


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