NavList:

After re-reading my previous post on Cape Belsham, I know I need to clarify.

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Ethiopics

Antarctica is discovered in 1820.  Some time between 1820 and 1855,  a whaler hunting elephant seals determined that the north point of Elephant Island was at S60°57' W54°56'.  The 1855 Ethiopic publishes this data, only 35 years after Antarctica is discovered. 

The 1867 and 1883 Ethiopics merely copy the data from the 1855 Ethiopic.

Compare to modern chart 29104.

The most northern point of Elephant Island is now known as Cape Yelcho.  The latitude of Cape Yelcho is S61°3'45".  There is a shoal with exposed rocks to the north of this point.  The northern most exposed rock of that shoal is latitude S60°58'  

I would expect that a seaman hunting elephant seals (hence the name of the island) would be able to determine which is the northern most point of Elephant Island.  If he includes the shoal with exposed rocks, then the latitude is correct within 1'.  If he determines that the shoal is separate, then the latitude is only correct to 6'45".  

In either event, the northernmost point of Elephant Island is no where near the minor point, today known as Cape Belsham.  

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Longitude.  

The 1855 Ethiopic states the longitude of the north point to be W54°56'.

Modern day Cape Yelcho is at longitude 55°21'15"; for an error of 25'15", an error of 12 nautical miles at S61°.

The shoal has a broad area.  The northernmost rock in that shoal has a longitude of W55°23', for an error of 27', an error of 13 nautical miles at S61°

Can we expect a whaler, prior to 1855, to know his longitude accurately?  Frank, can you clarify this point???

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What can Worsley see?

From his well documented location at Camp Wild, Worsley would not be able to see the low lying shoals north of Cape Yelcho.  They are 35'15" away in longitude, about 17 nautical miles at S61°.  They are below his horizon.

From his well documented location at Camp Wild, Cape Yelcho is blocked from view by an outcropping of rocks known as The White Company S61°5' W55°8'

The outcropping of The White Company would appear to Worsley to be that northern most point.  It's a mere 16'15" away from Camp Wild, 7.9 nautical miles away.

Note the obvious correlation between Worsley's stated 1 minute 4 seconds of chronometer error.  64 seconds divided by 4 seconds per arc minute yields 16' in longitude.  That's extremely close to the measured arc distance of 16'15"

Also, Worsley doesn't know it, but his reference in the Ethiopics misstates the longitude of Cape Belsham, the North point of Elephant Island. To reiterate it's stated in the Ethiopics as W54°56'. That's 25'15" to the east.

Worsley accounted for 16' of arc in his longitude correction. He needed to add another 13' or so of arc to get to Cape Belsham, from The White Company. That's his Cape Belsham, the next point over, modern day Cape Yelcho.  He can't see that.  That's 13'30" further west

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The Arithmetic

+25'15" Ethiopic Error east

-13'30" Error west, Worsley ID error 

-16'       Chronometer adjust, West

-4'15"    final position relative to Camp Wild in arc, 2 nautical miles to the east of the well documented location of Camp Wild.