The Beinecke Rare Book and Manuscript Library’s Vinland map could be a representation of North America dating from before Columbus sailed across the Atlantic Ocean. Or it could be nothing but a forgery.

The findings of two tests of the Vinland map were released this summer, but the controversy continues. One of the tests indicates that the map is from the mid-15th century, while the other calls the map’s authenticity into question.

Controversy has swirled around the map, which now is part of the Beinecke collection, since it was discovered in 1957. In 1965, it was given to the University anonymously, though the donor was later revealed to be Paul A. Mellon ’29.

One of the two recent tests examined a small sliver taken from the map and then used carbon-14 dating analysis to determine the age of the parchment. The results of the test were published in the journal Radiocarbon in an article written by Garman Harbottle, a retired senior scientist at the Brookhaven National Library; Jacqueline Olin, a retired research chemist at the Smithsonian Center for Materials Research and Education; and Douglas Donahue, a professor of physics at the University of Arizona.

“The test concluded that the parchment dated from 1434, plus or minus 11 years,” Harbottle said. “Eleven years sounds like a lot, but for carbon dating this is very accurate.”

Harbottle added that it is impossible to prove the map’s authenticity, but a forger would have had to draw the map before 1957.

“In those days, carbon dating was not known to the general public,” Harbottle said. “A forger could have gotten a parchment from the right date and drawn the map on it — [but] a forger would have had to be very lucky.”

Robin Clark, a professor of inorganic chemistry at University College London, said the carbon dating of the parchment does not prove that the map itself is from the mid-15th century.

“The parchment is old — but that isn’t the date of the Vinland map, which is defined not by the parchment but by the markings,” Clark said.

Clark released the results of his own analysis this summer. His article, co-written by Katherine Brown and published in the journal Analytical Chemistry, analyzed the map and said the titanium particle size and particle distribution in the ink show that the map is synthetic and thus of modern origin. The results confirm a previous analysis of the map by Walter McCrone, who was commissioned by Yale to analyze the map.

“You are very hard-pressed to find a reason for [the titanium substance anatase] to be found on a map if it does date from the [mid-15th] century,” Clark said. “Someone put it on is what I suspect, but then you are in the realm of speculation — there are only a few things we can say, but those things are pretty clear.”

Olin said she thought there should be further analysis of the ink.

“Without analysis of other inks, it is impossible to draw conclusions,” she said.

But Clark said he does not know what further tests are possible. McCrone used about three techniques to test the ink, Clark said. Thomas Cahill of the University of California at Davis, whose results found insignificant amounts of anatase in the ink, used another, and Clark’s own test used a third method of testing the ink.

“I think the ink problem is pretty clear and I’m not really sure what other tests could be practically done,” Clark said.

Robert Babcock, curator of early books and manuscripts at Beinecke library, said a scientific committee evaluates scientific proposals for the library.

“The Yale library has no role in authenticating this map or anything else in our collection,” Babcock said. “Our responsibility as a library is to preserve the material and to make it available to scholars for research. It is inevitable that scholars will interpret things differently and it’s not our role to arbitrate between those differing opinions.”

Harbottle said he thought Yale should take a step back and let people come up with new proposals.

“Nothing can prove authenticity,” Harbottle said. “All you can do is get closer and closer to authenticity. You can’t prove authenticity of anything.”