SPOILER ALERT: This post is very boring, and mostly pointless: not even flat earthers use this 'proof', and Dubay seems to have gone somewhat out of fashion, but I include it here because: a) I did the research already; b) others debunking his list on their blogs hadn't quite figured this one out; c) it's maybe good that it exists somewhere; and d) it's a great example of how Dubay has compiled, presented, and (not) researched his material. So... At number 13 in his list (video/self-published book/website) of "200 Proofs the Earth is not a Spinning Ball", Dubay says that: As usual, this is a fairly direct quotation from one of the Victorian flat earth texts, this time Samuel Rowbotham's "Earth Not a Globe" (1872): https://books.google.com.mx/books?id=VeBivA6QSEUC&pg=PT47&lpg=PT47&dq=rowbotham+biot+arago&source=bl&ots=2aR3V-9udm&sig=987ij9hMEVA5TGHe_h8H4U2I85o&hl=en&sa=X&ved=0ahUKEwis1Z3Z7bnOAhUG2WMKHbVZDjYQ6AEIKzAD#v=snippet&q="In the account of the trigonometrical operations"&f=false POINT 1: While almost repeated word-for-word, there are a few important changes to note. First of all, Dubay has chosen to call the "trigonometrical operations" a "French experiment" - probably to make it look like a flat earth test rather than the measuring of the globe that it actually was - and, rather than Rowbotham's "nearly the same" elevation of the two points, he has claimed they were "identical." This is a pretty amusing assertion, given neither he nor Rowbotham knew where the points actually were. POINT 2: Another fun one. When reading the text out, he says, "M. M. Biot", as though these were the guy's initials. "MM." actually means "messieurs" - ie, "Misters Biot and Arago." Biot's first name was Jean-Baptiste. TITBIT 1: Biot and Arago were two French physicists, astronomers, and mathematicians - and certainly not flat earthers - who, in 1806, took on the work of measuring the meridian arc which passes through Paris in order to determine the exact length of a metre. It was a pretty Herculean and adventurous task, taking many years and involved scaling mountains, being arrested as spies, and subsequent escapes from the Spanish authorities. Quite the dedication to science! POINT 3: The Desierto de las Palmas is a mountain range in the Spanish province of Castellón. The highest peak is called Bartolo, and it is from here that Biot and Arago made their measurements, as recorded on page 20 of "Memorial du Depot General de la Guerre, Volume 7". The elevations given are between 726.36 metres and 728.29 metres (2383 and 2389 feet). This demonstrates that Rowbotham clearly had no idea of the elevation of the summit of Desierto de las Palmas, since it would be impossible for the two points to be "nearly the same" - the highest point on Ibiza is 1558 feet, and this wasn't the point Biot and Arago were using. TITBIT 2: From "Report of Observations Geodesic, Astronomical, and Physics" by MM. Biot and Arago (1821): https://books.google.com.mx/books?id=3iYyAQAAMAAJ&pg=PA79&lpg=PA79&dq=observations+geodesiques+desierto+de+las+palmas&source=bl&ots=JgkxN7VeTq&sig=2LZulESyPdx7gR085a0GWsfRhqc&hl=en&sa=X&ved=0ahUKEwjcppuFirrOAhVCKGMKHRN8BqsQ6AEIHTAA#v=onepage&q=observations geodesiques desierto de las palmas&f=false POINT 4: While Biot and Arago called the point on Iviza (Ibiza) "Campvey", Dubay copies Rowbotham in calling it "Camprey": presumably because the original publication's "v" looks a little like an "r". Either way, I wasn't able to locate anywhere called Camprey or Campvey on Ibiza now - though, oddly, it shows up on some German sites as an Ibizan peak with an elevation of 396 metres. Handily, this matches the elevation reported by Biot and Arago, on page 9 of the aforementioned "Memorial du Depot" (and elsewhere), making it a good 1090 feet below the summit of Bartolo - ie, not exactly "identical." Using the metabunk curve calculator, and a distance of 100 miles (Rowbotham got that much right) this shows us that at least 224 feet of Campvey should have been visible from Bartolo. Claim #13, therefore, is debunked. FURTHER QUESTIONS 1. Where is Campvey exactly? A topo map of Ibiza locating a peak of 396 metres/1299 feet about 100 miles from Bartolo should do it. Or, in the aforementioned primary sources, latitude and longitude are given for Bartolo as 44.54/+2.56 and Campvey as 43.4/+1.09, but I can't work out what these refer to. Did they have a different system back then? After all, these measurements were taken a good 70 years before the prime meridian was established 2. In the 1870 edition (Volume 7, 4th Series) of "Chambers's Journal of Popular Literature, Science and Arts" the story of Biot and Arago is told, and it's possible this is where Rowbotham took his information, given that he uses the journal in some of his other 'proofs'. The Chambers account seems fairly scientific and straightforward, though, but I can't read all of it, as the digitised google books version isn't available in full-view. 3. Will I do research like this on any more of Dubay's 'proofs'? Hell no! Thorough investigation of this and "#4: Rivers Flow Uphill" (link to metabunk thread) - plus glances at some of the others - has told me pretty much everything I need to know. Hopefully the same can be said for any other sane-thinking person too. Sorry for the tedium!

I suspect this would be Camp Vell, on the northwest coast of Ibiza, which has an altitude of 400 metres on this topo map: http://mapsof.net/ibiza/ibiza-map The "ll" in Spanish is pronounced similarly to a "y", which would explain the spelling. It is also just about the closest point in Ibiza to Bartolo. The distance between Bartolo and Camp Vell from peak to peak appears to be almost exactly 100 miles:

I found a citation that confirms that Camp Vell was the peak in question: From page 537 of Actes de la VIII Trobada d'Història de la Ciència i de la Tècnica, by Josep Batlló Ortiz of the Institut d'Estudis Catalans (2004). https://books.google.co.uk/books?id=zntAhCCnvxgC&pg=PA537&lpg=PA537&dq=biot+arago+camp+vell&source=bl&ots=r8LPLC0ClV&sig=uvvKTnxnps8zXaO-TsPzd7kmnmg&hl=en&sa=X&ved=0ahUKEwiX8-Glp7rOAhXCDsAKHUDCAqkQ6AEIHjAA#v=onepage&q=biot arago camp vell&f=false Translation of second paragraph from Catalan:

I also don't follow the logic here: The heights being identical have nothing to do with the line of sight. What Dubay (or rather Rowbotham) seems to have done is decided that the view between two peaks of identical heights is the same as the view from sea level to sea level, which will be where he got his 6600ft figure from: In fact, of course, the view between two peaks of identical height depends entirely on the height of those peaks. If the view from each one is greater than 50 miles (half the distance between them) then the peaks will be intervisible. Using the calculator, and a bit of trial and error, you can see that they only have to be taller than about 1667ft: The best measurements I can find for the peaks in question are 729m (2392ft) for Bartolo and 400m (1312ft) for Camp Vell. Using the curve calculator, we get a horizon distance of about 60 miles and a hidden height of 1073ft from Bartolo: and a horizon distance of about 44 miles and a hidden height of 2065ft from Camp Vell: In other words, the top 240ft of Camp Vell should be visible from Bartolo, and the top 327ft of Bartolo should be visible from Camp Vell.

I appreciate these debunks because it really shines a light on how the flat earth movement has operated since it's inception over a century ago. Half of the proof comes from simply not understanding how a round earth works, and half comes from deliberate obfuscation or falsification. Some small portion is simply being so loose and free with the facts that little things like names get mangled on the way by, as well. I'd love to see more, but I imagine that the amount of research it takes is simply not worth the result, so I'll have to be satisfied with these.

Nice work @Trailblazer! The mystery of Camp Vell is solved. I'd happily do more, if they were requested, and hadn't already been debunked on some of the excellent blogs that deal with this list. For my own purposes, I feel pretty satisfied, but if it's good for others I'll gladly get stuck in. It is quite good fun.

I am little confused When I add the two heights the 728 meters and the 396 meters to get 1124 meter. When I calculate the horizon for this height I only get 120 km which is a 40 km short of the 160 km distance between the two mountains (100 miles ) what Am I doing wrong in assuming that adding the 2 heights to a one location is equivalent to having each location with its specified height

Why are you adding the two heights together? Where does the idea to do that come from? Perhaps drawing a diagram for yourself would help?

You can easily derive mathematically that the sum of the heights will not give you the total distance, starting from the 8 inch /mile squared rule. Put youself somewhere in the middle of the two heights ("on top of the bulge"). Then the distance to one side, let's call it d, equals the square root of h/8 and the distance to the other side, say d', equals the square root of h'/8. Now the total distance, d + d', which is the square root of h/8 plus the square root of h'/8, clearly is not the square root of (h + h')/8. But a diagram should do the trick as well.

Thanks Hink/Rory After looking how the relation between distance to horizon and height was derived it is clear now. It is not linear relationship as in y = cx it is as in y= c * sqrt( x) Thanks very much

I posted the above on another flat earth forum and was met with a multitude of strange and preposterous objections. À la Wallace, if I'd been a smarter man I wouldn't have got involved - but I'm not, and I felt compelled to prove that the summit in question was indeed Bartolo. Hence the following: 1. "Recueil d'observations géodésiques: astronomiques et physiques" (1821) is a 600-page book by M.M. Biot and Arago which details how they measured the Paris meridian arc and determined the exact length of a metre. You can find the full book here at Google Books. 2. From page 79 they detail their time taking measurements between Desierto de las Palmas and Campvey (Camp Vell) in Ibiza: 3. "M. Mechain" - "M." means "Monsieur" (and "M.M." means "Monsieurs") - refers to Pierre Mechain, an astronomer and surveyor whose work they were continuing: he had died in the vicinity of Desierto de Las Palmas in 1804 while on the job. 4. They also mention that Mechain had established an observation point "at a small hermitage" at "the highest peak of Desierto de las Palmas", and this is where they made their measurements from - an elevation enabling them not only to see Ibiza, 100 miles away, but also to Formentera, another 20 miles more distant. From "Valencia pintoresca y tradicional: personajes, hechos, y dichos ..., Volume 1" (page 228): 5. The hermitage of San Miguel is still there, right on the summit: 6. In Arago and Biot's meticulous accounts of their measurements, they don't mention the summit as being called "Bartolo", but refer to it repeatedly as "Desierto de las Palmas". They do, however, record their elevation, as shown on pages 20-21 of Mémorial du Dépôt général de la guerre, Volume 7 (1840): The elevations of the observation points are all around 727-728 metres; Bartolo is recorded today at 729m, while the next highest peaks in the range are at around 670m. In total, there are 29 mentions of Desierto de las Palmas in this 714-page book, and 19 of Campvey (their observation point recorded by them here as being 397m in elevation; whereas we have the summit of the mountain at between 396 and 400m). Note also the reference to the observation point at "Mongo" - mentioned 19 times - at 713-714m: "Montgo" (Spanish) is a mountain 89 miles to the south of Bartolo which rises to a total of 753m. 7. These three peaks form a triangle from which they made observations, as shown in the map below (thanks Edby): On page 2 of "Mémorial du Dépôt..." they mention the three peaks and the distance of one of the sides: Note: If you translate "toise", you are given "fathom", and if you type "82555 fathoms" into google, you are returned with a figure of around 150 kilometres. The pre-1812 "toise", however, was slightly longer than a fathom - 1.949m compared to 1.8288 - and therefore 82555 "toises" is equal to 160.9 kilometres. This is confirmed in "The Literary Panorama, Volume 5" (1809), in their report of Mechain, Biot, and Arago's measurements: The google map distance from the summit at Bartolo to the summit at Camp Vell is 160.9km. 8. The reason they didn't record the summit as "Bartolo" is because it wasn't called that then: 9. The same site - a local history site, in Catalan - also mentions the following: 10. In a nutshell: it's Bartolo.

Question: on page 9 of "Mémorial du Dépôt..." the longitudes and latitudes are given for Bartolo, Camp Vell, Montgo, and other observation points - but they're not using the system that we use now: I'm assuming there's a way to figure out how these relate to the figures we use now. Anybody know?

It says: https://aty.sdsu.edu/explain/extinction/centesimal.html So if there's 400 centesimal degrees in 360 degrees, and 10,000 centesimal seconds in one centesimal degree That suggests you can just write the number as a single decimal, and multiply by 360/400 (or 90/100, or 9/10, or 0.9) the first latitude of 45. 1271.43 is 360/400 * (45.127143) = 40.6144287 degrees.

Nice one. Love it. Now in testing I find it needs a little fine tuning - for Arago and Biot were using the Paris meridian rather than the Greenwich meridian. The Paris meridian is at longitude 2°20′14.03″ east - or 2.337231 in modern money. If we subtract the converted longitude figure from this, it will give us a current system coordinate. To test: Arago and Biot record Barcelona Cathedral as being at 45.9827.39, 0.1791.22 To convert, remove the second decimal point and multiply by 0.9 This gives us 41.3844651, 0.1612098 Now subtract 0.1612098 from 2.337231 Final 'modern' coordinates are 41.3844651, 2.1760212 Check on google maps: Et voila: Arago and Biot have their coordinate just over 23 metres from the front door of the cathedral. Now for Bartolo, at 44.5402.86, 2.5639.79 - which converts to 40.08625074, 0.0296499: This time I make it 143m from where our modern day coordinate would have it. And Camp Vell, at 43.4003.07, 1.093863 - which converts to 39.0602763, 1.3527543: This time 195m from where we have it. So, on the one hand there's a very high correlation between coordinate systems. And on the other, we have no idea which one is more accurate - the early-19th century French one, or google maps with all its satellites and ting. The final thing we can check is the distance between Bartolo and Camp Vell using the coordinates provided by Biot and Arago. Google maps make it 160.85 kilometres - or, if we convert that to the unit used at the time, that's 82,530 toises. The difference between this modern measurement and their 1806/1807 measurement, made using telescopes and lamps over a distance of 100 miles, is a shade under 50 metres*. I find that quite remarkable. (*The actual distance between the peaks is 10m further than the distance at sea level - so maybe they were 40m off. Or maybe google is off and they were right.)

Well, I see from Wikipedia that Arago was a freemason: https://en.wikipedia.org/wiki/François_Arago That explains everything! But seriously, Arago was a titan of science, one of the greatest figures in an age that included the likes of Ampere, Fresnel and Faraday. Anyone reading about the history of optics, electricity, or astronomy will come across his name all the time. I was just surprised to see that he would spend any of his valuable time trekking around the mountains of Spain with telescopes and lamps, but I see from the Wiki entry that this was done very early in his career, starting when he was only 20. He settled down a bit later. Just reading the list of his achievements makes me feel very, very lazy.

One thing I've noticed in looking at Biot and Arago's coordinates is that all the ones I've done - which is only 6 or 7 - are located to the northwest of the google maps coordinates. Not sure what that means.

Magnetic North moves around, so maybe 200 years has made a difference in that regard. Don't know if that is relevant to these measurements.

Last time I went to Greenwich I checked the co-ordinates using the GPS on my phone. If you stand on the prime meridian line marked on the ground, it reads about 0°00′05″W. The point where you get "all zeroes" of longitude is about 100 metres further east. It's annoying (PS: maybe Dubay could read "Myth 2" on that link as well!) Spoiler

Here's your "figure below" included: Figure 1: three points with the same latitude and longitude in three different coordinate systems. The map extract is 200 metres square.

This has now been digitised. Doesn't really add anything, but I include it here for completion: https://books.google.com.mx/books?redir_esc=y&id=vLLQAAAAMAAJ&focus=searchwithinvolume&q=desierto

I went to Camp Vell the other day, was pretty cool to be standing in the spot where Biot and Arago were all those years ago. There's a survey monument on the top: There was also a 60-foot tall fire tower nearby: amazing views from up there, over the entire island. Could just make out the mainland of Spain, eighty to a hundred miles away.