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Hello, Jim and Wolfgang!

Wolfgang Köberer wrote:

“And Charles Green, the astronomer on Cook’s first voyage wrote to the secretary of the Royal Society on 28 November 1768: “I thought it a little odd when I found that no person in the ship could either make an observation of the Moon or calculate one when made.” “No person” apparently included Cook, who – as his biographer Beaglehole wrote, showed “a more lively interest”, without being able to say exactly when he learnt the technique (Beaglehole, The life of Captain James Cook, Stanford, Calif. 1974, 116). So it is also unlikely that Cook practised the lunar distance method when charting in North America.”

It is really strange. There are enough evidence that J.Cook himself practiced lunar observations during the “Endeavour” voyage. And this was done also before 28. november, 1768.

For example, let’s take a look into Journal by James Cook 28.october, 1768. Cook wrote:

“At a little past 1 a.m. Longitude in by the 3 following Observations—viz., by the Moon and the star Arietis, 32 degrees 27 minutes; by the Moon and Pollux, 32 degrees 0 minutes 15 seconds; by ditto, 31 degrees 48 minutes 32 seconds; the mean of the whole is 32 degrees 5 minutes 16 seconds West from Greenwich, which is 31 minutes more Westerly than the longitude by account carried on since the last Observation. The two first observations were made and computed by Mr. Green, and the last by myself.”

Or another example from Journal by James Cook 29.december, 1768. Cook wrote:

“Between 9 and 10 a.m. took 7 sets of Observations between the sun and moon to find the Longitude of the Ship. Each set Consists of three Observations; the Mean of the whole gave 59 degrees 18 minutes 34 seconds West of Greenwich. The result of each set was as follows: viz., 1st set, 59 degrees 8 minutes; Second, 59 degrees 21 minutes; Third, 59 degrees 34 minutes; Fourth, 59 degrees 17 minutes; Fifth, 59 degrees 11 minutes 45 seconds; Sixth, 59 degrees 19 minutes 30 seconds; and the Seventh, 59 degrees 20 minutes 45 seconds. The greatest differance between any two—viz., the first and third—is but 26 minutes, and the mean of these two differ from the mean of the whole only 2 minutes 26 seconds. This shews to what degree of accuracy these observations can be made even by Different Persons, for four of these were made and computed by Mr. Green and the rest by myself.”

And  another example from Journal by James Cook 31.march, 1769. Cook wrote:

“A.M. took several Observations of the sun and moon, the mean result of them came within 8 Miles of Yesterday's Observations computed both by Mr. Green and myself.”

In fact we can easily check information about the observers on board HMB “Endeavour”. The best easy access source, in my oppinion, is Astronomical observations during this expedition (published by William Wales in 1788). W.Wales collected all the observations recorded by Mr. Green and published them. And he clearly indicates who was the observer of the particular observation. Of course, the most part were made by Mr.Green (after his death by Mr. Charles Clerke). But one part is made by Cook himself.

The first J.Cook’s observation in this book is recorded on 15. october, 1768. As you can see, this date is before 28. november, mentioned in the Green’s letter. Therefore we can conclude that it is not true that J.Cook himself was not able to make Lunar observations during his first expedition around the world.

Wolfgang Köberer, Could you, please, publish all the letter from Mr. Green. It would be interesting to see the full context.

Jim Wyse you wrote:

“I'm doing an 'amateur hobby project' based on James Cook's coastal charting activities.  There seems to be lots of info on Cook's use of lunars during his voyages in the Pacific (1768 and later) but very little (it seems) on his use of lunars during his years in NE North America (1767 and earlier).” 

I agree absolutely with Wolfgang Köberer that it is unlikely that Cook used lunars during survey of Newfondland. I have read some papers of Cook’s Newfoundland surveys and there we can found some information regarding this issue. I am attaching two pdf files. In the file ending with_002 (page 398) we can read that Cook did not accertained longitude (except the eclipce of the Sun case in 1766).

Here are my thoughts about Lunars and Cook in Newfoundland.

The year of 1767 is a milestone in the history of Lunars. Practising Lunars before this year is radically different process than after this year. And this is because of publication of the first nautical almanac with predicted lunar distances. This made possible to do all the neccessary math quite easily.

What was the situation regarding Lunars befor 1767? In 1763 Nevil Maskelyne published his “The British Mariner’s guide”. He described the process of getting longitude by lunar observations without almanac data. All these data had to be calculated for each individual case. The accuracy was expected about 1 degree of longitude. But the calculations were very time consuming (about 4 hours). I have worked some examples using the “Mariner’s guide”. And indeed, I found that these calculations are not complicated from mathematical point of view, but they are long and any small mistake can lead to wrong result. Besides I found that the position of the Moon and the Sun, calculated using tables in “Mariner’s guide”, differs from values in almanac ( I compared some data from 1769 almanac). The difference can reach at least 1’ (meaning additional 0,5° error in longitude).

This “Mariner’s guide” method was practiced not only by Maskelyne himself in his St. Helena and Barbados expeditions, but also by some enthusiasts on board of East India and other ships. Maybe the best known is HMS “Dolphin” expedition (1766-1768). All the observations are available (published by W. Wales). During this expediton the island of Tahiti was discovered for Britains. And it’s longitude was accertained by lunar method. The observations and calculations on board the ship were done by Mr. Harrison (the purser; but this is not the chronometer's Harrison!).   And all of them were calculated by this long method from “Mariner’s guide”.

And now about Lunars and Newfoundland. This is period befor nautical almanac was published. Even assuming Cook practised Lunars, if he blindly relied on the results obtained from lunar observations, his maps would be much less accurate, because the accuracy of lunars is significantly lower than the accuracy of his survey methods. The reference points thus obtained are too inaccurate for dimensions of such an island as Newfoundland. If the reference points are in error of, say 1 degree, than all the coastline would be inaccurate.

To get more or less relieable reference points from Lunars, he would have to make hundreds of observations from one position (as it was typically done during his and other explorer’s expeditions) and calculate all these observations by the above mentioned long method. And even if he had done it, the results would be less accurate than methods he practiced.

And we must not forget that Cook was an expert in surveying the coasts. Methods he used are known and published (I am attaching one such pdf file, if someone is interested; file is ending with_001) . Besides the work was done during quite long period of time.

Thanks to Jim for starting this discussion. It would be nice to hear some coments from those who have studied Cook’s papers more deeply.

Modris Fersters

[NOTE from FER: The first document by Whiteley (1974) here is legally protected by copyright. I'm still looking for a safe external link. This pdf copy will remain available here for 24 hours. If it interests you, grab it now! :) ]