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Hi Frank

Valid points all.

The determination of chronometer error by the method selected is subject to 
errors in the input values, which are (1) latitude (2) altitude and the 
estimation of the error is subject to the knowledge of the longitude, so that 
the navigational triangle can be solved.  Injecting a 1 arc-minute error in 
latitude gave me a three arc minute error in longitude for example.  Guessing 
at or improper knowledge of the values will yield improper chronometer error 
determinations.  Even Worsley states that his chronometer was slower than he 
thought.  He must have been aware of this issue.

Your point regarding 'how well he could have known his position" is true.  My 
library doesn't have the requisite tomes to do the research here, so I will 
send a general appeal to the NavList.  The expedition sets off from South 
Georgia Island on 5 December 1914, two years before the log we are 
investigating.  This is an outside terminus for published information. If 
your information about Cape Belsham predates that, even by alot, it is worth 
while knowing.  Calling all NavList members, what do you have for either Cape 
Belsham or Point Wild, both about a mile apart on Elephant Island.  

I will offer my copy of Norie's "Epitome of Navigation" 1848, in which 
Elephant Island - Cape Valentine is given as South 61 degrees 5 minutes West 
54 degrees 55 minutes.  Cape Valentine is the easternmost portion of Elephant 
Island.  Navigation Chart 29104 gives this as South 61 degrees 7 minutes 15 
seconds West 54 degrees 38 minutes 15 seconds.  There is a significant 
discrepancy in longitude there, about 17 arc minutes.  Without an accurate 
chart, however, Worsley would not have been able to determine the lat lon of 
Point Wild with any degree of accuracy. Why Norie's and not Bowditch?  
Because this was an English expedition.  Bowditch was from those upstart 
colonies hehehe.  

The grail of all of this would be the chart(s) that Worsley used.  Perhaps we 
can share that type of data with the list.  If we could see what he used, 
then we would have an understanding of the values.

This all begs the point of what Worsley's chronometer error SHOULD have been.  
For this I have used the modern navigation chart 29104.  Henry has indicated 
some international intrigue about some other value and I am sure he will 
share that with us.  From this we can see what his chronometer error really 
was and why he thought he was further east than he really was.

Best Regards
Brad
  


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