A historian friend is looking for a help in analysing Magellan’s Navigation - any suggestions?

[Roberto]

Do we know details of the instuments he had on board?

The introduction of the document explains they had a table with daily sun declination, they took a noon sun height (quadrant/astrolabe are mentioned) and by +-declination and 90° they derived latitude.
Remarkably correct, a few descriptions of land correspond exactly with known geographica places.

Looking at the month of January, after having rounded South America they keep a NW course and their latitude decreases sometimes by around one half degree per day, gosh that makes their speed around 2 knots. No wonder they called it "Pacific"

 

[newtothis]

Ah, 'never read it'. I see......

To be fair, I've not read Mein Kampf but am quite happy opining that it's not very good political writing.

 

[newtothis]

Has it been debunked then? I read it when it came out and a lot of it sounded like a slam dunk to me (and I'm a confirmed skeptic) . There were bits that were obviously nonsense. One bit that sticks in my mind as being nonsense was where he adjusted their track to 'correct' the longitudes which they wouldn't have known. Of course if you take any line going north south and change the longitudes to fit the known coast you errrrr, get a line that fits the known coast!


EDIT: I've Googled. It seems to be the bit that's considered bollocks is the America bit. It's a long while since I read the book but my recollection is he was far from emphatic about that. Certainly I came away with the impression it was a plausible theory waiting for evidence. Not that he was saying it 100pc happened. Pretty sure the rest of it was pretty mainstream. Maybe my memory is flawed, of course. If people don't like that they're really gonna hate ancient history. People writing 500 page books when all the evidence is half a page of Tacitus always makes my chuckle.

The criticism goes beyond the Americas claim:
"The reasoning of 1421 is inexorably circular, its evidence spurious, its research derisory, its borrowings unacknowledged, its citations slipshod, and its assertions preposterous ... Examination of the book's central claims reveals they are uniformly without substance."

 

[capnsensible]

It's a big jump from ' I read that book and its rubbish' to ' I haven't read that book but its obviously rubbish'.

If I haven't read a book, I refrain from comment. Its the way I was taught.

 

[newtothis]

I would say a book on creationism was obviously rubbish without reading it. And when leading historians say a book on their specialist subject written by a not very successful submariner who left school at 15 is rubbish, I tend to go with the historians.

 

[capnsensible]

I would say a book on creationism was obviously rubbish without reading it. And when leading historians say a book on their specialist subject written by a not very successful submariner who left school at 15 is rubbish, I tend to go with the historians.

Do you read what the leading historians said? Who actually said they were leading? Did someone write about it?
This just goes round and round.
Anyway looks like the OP may be making some headway. Good one.

 

[JumbleDuck]

It's a big jump from ' I read that book and its rubbish' to ' I haven't read that book but its obviously rubbish'.

If I haven't read a book, I refrain from comment. Its the way I was taught.

I trust the opinion of informed commentators.

 

[Gary Fox]

It's a big jump from ' I read that book and its rubbish' to ' I haven't read that book but its obviously rubbish'.

If I haven't read a book, I refrain from comment. Its the way I was taught.

 

[newtothis]

Do you read what the leading historians said? Who actually said they were leading? Did someone write about it?
This just goes round and round.
Anyway looks like the OP may be making some headway. Good one.

Felipe Fernandez-Armesto joined the history department at the University of Notre Dame in 2009, after occupying chairs at Tufts University and at Queen Mary College, University of London. He had spent most of his career teaching at Oxford, where he was an undergraduate and doctoral student. He has had visiting appointments at many universities and research institutes in Europe and the Americas and has honorary doctorates from La Trobe University and the University of the Andes, Colombia.
vs.
Menzies dropped out of school when he was fifteen years old and joined the Royal Navy in 1953. He never attended university and had no formal training in historical studies.

 

[Laminar Flow]

(I say the above having been under the impression that they didn’t really know how to calculate/keep longitude in those days - but that’s only from the best-sellery book from a few years ago… I really should learn more about this stuff, being a geography lecturer and a yachtsman!)

Longitude was established by dead-reckoning and was highly unreliable. Even then, the common practice of latitude navigation was anything but accurate. Columbus' navigation was pretty atrocious and his latitude estimates (to be kind in regards to the technical process) wildly inaccurate. Even the whole concept of declination was not yet well established, if at all. The tools for taking a sight, astrolabium and Jacob's staff, were inaccurate and awkward to use aboard ship.

Once beyond the descriptive rutters of his antecedants and out of sight of known land, Magellan and his crew would have been flying blind, at the very least until he reached the coasts of Africa and only then if he had access to or knowledge of the reports by Vasco da Gama, which might be unlikely, as such things were kept secret at the time.

I have read the book by Mendes and to even call it conjectural is overegging it.
My first point of doubt is in regards to the supposed size of his ships: as someone with a technical interest in sailing craft I would consider it implausible that one can design and build a ship of 450' in length in wood (any wood) that will hold together on the high seas and can be propelled by what are essentially freestanding masts sporting a single sail, even if there were nine of them (do the SA/D ratio on that one). The biggest sailing ship ever was the Preussen and that was only technically possible with the use of steel.

The section regarding the exploration of the Americas is rubbish. Trading on the seasonal monsoons, however was well established and there is plenty of archeological, historical and also genetic evidence of trade between Africa and the Far East. The rest is embellishment.

 

[capnsensible]

I trust the opinion of informed commentators.

I said it would be controversial. Interesting to see which posters donned their big wellies and jumped right in! ??

For the record, I found it a big stretch and not convincing. But at least I read it! ??

 

[Laminar Flow]

The introduction of the document explains they had a table with daily sun declination, they took a noon sun height (quadrant/astrolabe are mentioned) and by +-declination and 90° they derived latitude.
Remarkably correct, a few descriptions of land correspond exactly with known geographica places.

Looking at the month of January, after having rounded South America they keep a NW course and their latitude decreases sometimes by around one half degree per day, gosh that makes their speed around 2 knots. No wonder they called it "Pacific"

Well, they did have a rough idea where they were going, i.e. the Spice Islands, but, unfortunately for the Spanish, that part of the world had been "ceded" to the Portuguese by His Holiness in the Treaty of Tordesillas.

 

[Kukri]

Mention of Zheng He and his seven voyages reminds me of my own pet theory, so here it is:

Here’s my theory of how those reefs in the South China Sea came to loom large in the politics of 2021:

As everyone knows, during the reign of the Yongle Emperor of Ming, the celebrated eunuch Admiral Zheng He commanded a series of voyages with a fleet of large junks, which certainly got as far as present day Somalia.

Zheng He - Wikipedia

As is slightly less well known the Ming court was divided between the eunuch faction and the Confucian mandarin faction. The eunuchs of course controlled the Emperor’s sex life whilst the bureaucracy controlled the taxes.

After the death at sea of Zheng He there was a palace coup by the mandarin faction, who had been horrified by the non-Confucian idea of actually leaving China and, perhaps worse, by the spending of a great deal of money.

The triumphant mandarins passed a law banning, on pain of death, any Chinese person from owning a vessel with more than two masts or going more than three li from China.

This even has a name - it’s the Sea Ban, the Hai Jin:

Haijin - Wikipedia

This did not suit the merchants of Guangdong province, who had been in the habit of trading with Southeast Asia for centuries, and who were not about to stop... “Heaven is high, and the Emperor is far away” is a Cantonese expression...

The answer was to observe that the Emperor had not stated where China started and stopped, and to draw maps showing that China stopped three li short of any other land.

Hence that line running three li outside the coasts of all other lands bordering the South China Sea.

Everyone now happy; junk trade with Luzon, the Visayas, Mindanao, Borneo and Vietnam resumes, in due course the Spanish occupy the Philippines with the sole purpose of trading with China and vast amounts of Mexican silver are carried from the mines of Potosi, in Mexico, to Manila, where they are traded for silks, porcelains and other luxuries which are shipped back to Mexico in the Manila Galleon and then carried overland to the Atlantic and thence to Spain. A Manila Galleon was built once a year in Manila and made one round voyage; after that she was worm eaten and worn out. Commodore Anson’s rather absurd orders were to sail round the world, find the Manila Galleon and capture her, which is precisely what he did.

In the 1880s the French colonial government in Vietnam occupies one of the reefs in the South China Sea, and the Dowager Empress of China asks her Collector of Maritime Customs, Sir Robert Hart, where it is. Not strong evidence of owning it!

Zheng He was forgotten until 1905 when a nationalist scholar discovered him and published a biography.

In the early 1940s the Roosevelt administration decides to repeal the Unequal Treaties and sets up meetings with the Kuomintang government in Chongqing to agree the terms. This puts the onus on the Chinese government to decide on what it wants back. There is a good deal of poking around in archives and up pops the chart with the eleven dash line. This along with the return of Hong Kong is demanded.

Final agreement is delayed whilst the Late Unpleasantness With Japan is dealt with, and then to everyone’s surprise China is taken over by Mao Zhedong’s version of the Communist Party.

Mao’s Prime Minister and Foreign Minister is Zhou Enlai. Zhou inherits the claim to the eleven dash line, looks at it, re-draws it with nine dashes, and, aware that the People’s Republic has no means of asserting the claim, puts it back in the file.

Time passes. Zhou dies in office, and in death becomes the greatest statesman China has seen in centuries (probably true). Mao was “70% right” but Zhou was 100% right.

In modern China, criticism of the Communist Party is unacceptable except that people can always criticise the Party for not being patriotic enough.

The map is dug out again. “What is being done to secure Zhou’s Nine Dash Line?”

 

[kaj]

"Magellan, der Man und Seine Tat" by Stefan Zweig.

I have a translation, 1938, to my fathertongue.

 

[AntarcticPilot]

To get back to the original topic, I have published analyses of historical navigation (19th century). The navigation in question was that of James Clark Ross' Antarctic expedition in the region of James Ross Island (NOT Ross Island!) and Nordenskjiold's expedition in the same region (Nordenskjolds was particularly odd!). These are in "Historical observations of Prince Gustav Ice Shelf", Historical observations of Prince Gustav Ice Shelf | Polar Record | Cambridge Core. Sorry - no free text available.

I'd repeat all the comments about longitude being little better than guesswork in those days. Latitude was (theoretically) available, but the instruments to make it easy to obtain on board ship were not yet available; the astrolabe was the usual method, and that required a steady platform as it obtained its horizontal reference by being hung vertically. The cross staff was JUST coming into use in Magellan's day, but a) it required the navigator to look straight at the sun (navigators often became blind in one eye while this instrument was in general use!) and b) was difficult to calibrate, and lost accuracy at low latitudes. I'd imagine that getting latitude to a degree would be an achievement, and at sea, they'd be doing well to get it to that level of accuracy. For long periods, they would have no good observations and simply went by dead reckoning. Of course, they didn't know about the various ocean currents, which meant their longitude estimates would be increasingly "off" as they proceeded. Magellan predated Galileo's discovery of the moons of Jupiter, which provided a good (land-based) method of finding longitude by nearly a hundred years! You can't observe the moons of Jupiter from an unsteady platform - you need a reasonable telescope, and that in turn requires a steady platform.

 

[Roberto]

Well, they did have a rough idea where they were going, i.e. the Spice Islands, but, unfortunately for the Spanish, that part of the world had been "ceded" to the Portuguese by His Holiness in the Treaty of Tordesillas.

Then they cleverly made appeal and a few years later came the Treaty of Zaragoza, where they declared the antimeridian to the one in Tordesillas as partition for that other part of he world.

Thinking of it, not being able to determine longitude was a minor detail, they knew they wanted to go west, when they met land they went south, then round land and up north again, and so on, continent after continent

 

[Roberto]

"Magellan, der Man und Seine Tat" by Stefan Zweig.

I have a translation, 1938, to my fathertongue.

Which is a novelist re-writing of Antonio Pigafetta account (the member of Magellan expedition who wrote the original story)

 

[Laminar Flow]

Then they cleverly made appeal and a few years later came the Treaty of Zaragoza, where they declared the antimeridian to the one in Tordesillas as partition for that other part of he world.

Thinking of it, not being able to determine longitude was a minor detail, they knew they wanted to go west, when they met land they went south, then round land and up north again, and so on, continent after continent

Before my first ocean crossing I was quite anxious about my navigation. I asked another sailor, while we were in the Canaries, how he managed: "Oh," said he, "every few days I take a noon sight, that's good enough. Besides, when you cross an ocean, you are bound to hit land somewhere on the other side." He went on to tell me he had lost 5 boats in his sailing career which gives me little confidence in this methodology.
Even with the most careful practice, navigation by deadreckoning is uncomfortably inaccurate. Sure, you will eventually hit land, the question is when and where.
The entrance to the Straight of Juan de Fuca in the Pacific North West is a prime example: The target is a mere 30 miles wide and there are, quite literally, hundreds of wrecks either side, of ships approaching from the open Pacific and that were unable to fix their position, possibly for days or weeks, due to the frequently overcast skies.

 

[Laminar Flow]

To get back to the original topic, I have published analyses of historical navigation (19th century). The navigation in question was that of James Clark Ross' Antarctic expedition in the region of James Ross Island (NOT Ross Island!) and Nordenskjiold's expedition in the same region (Nordenskjolds was particularly odd!). These are in "Historical observations of Prince Gustav Ice Shelf", Historical observations of Prince Gustav Ice Shelf | Polar Record | Cambridge Core. Sorry - no free text available.

I'd repeat all the comments about longitude being little better than guesswork in those days. Latitude was (theoretically) available, but the instruments to make it easy to obtain on board ship were not yet available; the astrolabe was the usual method, and that required a steady platform as it obtained its horizontal reference by being hung vertically. The cross staff was JUST coming into use in Magellan's day, but a) it required the navigator to look straight at the sun (navigators often became blind in one eye while this instrument was in general use!) and b) was difficult to calibrate, and lost accuracy at low latitudes. I'd imagine that getting latitude to a degree would be an achievement, and at sea, they'd be doing well to get it to that level of accuracy. For long periods, they would have no good observations and simply went by dead reckoning. Of course, they didn't know about the various ocean currents, which meant their longitude estimates would be increasingly "off" as they proceeded. Magellan predated Galileo's discovery of the moons of Jupiter, which provided a good (land-based) method of finding longitude by nearly a hundred years! You can't observe the moons of Jupiter from an unsteady platform - you need a reasonable telescope, and that in turn requires a steady platform.

The first quadrant, for which an accuracy of one minute of arc was claimed, in theory 1 nautical mile, was not invented until 1631 - well past Senior Magellan's time.

 

[AntarcticPilot]

The first quadrant, for which an accuracy of one minute of arc was claimed, in theory 1 nautical mile, was not invented until 1631 - well past Senior Magellan's time.

Yes; the cross-staff was the earliest practical means of measuring the elevation of a celestial body, and the earliest mention of it only just predates Magellan's circumnavigation (1515, if my memory serves). The quadrant and its successor the sextant were the first instruments capable of accuracy in the region of a minute of arc; the sextant was specifically developed to measure lunar distances to determine longitude (the quadrant can only measure angles up to 90 degrees; the sextant up to 120 degrees)

The Vikings had a means of measuring the elevation of the sun, but it wasn't calibrated - you could use it to check if you were on the latitude of a place you'd previously visited, but not measure the latitude. It was basically a rectangle of wood on a string; you held the end of the string at your nose, and one edge of the wood was on the horizon and the other on the relevant celestial body. The length of the string fixed the angle. If used with Polaris, it would be reasonably reliable.