For those unfamiliar with it, the story concerns the accidental discovery of an account of a previously unknown and possibly fictional region of the Middle East called Uqbar, a discovery that leads in turn to the revelation of the supposed existence of a previously unknown planet that turns out to be, at least at first, an elaborate hoax perpetrated by a conspiracy of scholars over the course of several centuries. The story begins when the narrator — unnamed, but we are justified in calling him Borges — is having a conversation with his fellow writer and occasional collaborator Adolfo Bioy Casares. Both men are unsettled by the presence of a mirror in the villa where they are staying, and Bioy observes "that one of the heresiarchs of Uqbar had stated that mirrors and copulation are abominable, since they both multiply the numbers of man." Borges is intrigued by the citation and asks its source; Bioy says that he found it in the article on Uqbar in The Anglo-American Cyclopedia. By chance, there is a set of that work in the villa, but it proves to have no article on Uqbar. Borges half suspects that his friend has concocted a false source to cover his own witticsm, but the next day Bioy telephones to say that he has checked his own copy and found the article in question, which he subsequently shows to Borges. And it goes on from there.
According to my commemorative hardcover edition of Ficciones (El libro de bolsillo, Alianza Editorial, 2006), at the villa Borges and Bioy first look for the article on Uqbar at the end of Volume XLVI (46), which ends with "Upsala" and the first pages of Volume XLVII (47), which begin with "Ural-Altaic Languages." The missing article on Uqbar, however, is found in Volume XXVI of the set Bioy possessed, that is, in the twenty-sixth volume, not the forty-sixth. The narrator makes no comment on this curious fact.
My copy of Ficciones was bought to replace an essentially identical paperback copy that had fallen apart (and which I have since discarded). The copyright information has been updated, but the cover art, layout, and typography are presumably identical to the edition I used for years, except for the garish belly band and a small green square on the cover. In either form, the text originated as a Libro del Bolsillo in 1971 and was revised in 1974 under the author's supervision; it has presumably sold hundreds of thousands of copies. I have two translations of the story on my shelves, both from the early 1960s. One, in a volume that uses the Spanish title Ficciones, was translated by Anthony Kerrigan. The other, in a collection entitled Labyrinths, was translated by James E. Irby. (I don't have a copy of Andrew Hurley's newer translation.) In both editions, it is in Volume XLVI that Bioy finds the article on Uqbar; there is no discrepancy.
"Tlön, Uqbar, Orbis Tertius" was orginally published in the literary magazine Sur in 1940. (In the version that was published in book form there is a postscript dated 1947, but that date may be a fiction.) It's possible that both Kerrigan and Irby noticed the "error," if that's what it was, and silently corrected it, but it seems more likely that the misprint crept into a later Spanish-language edition. I haven't been able to access Sur online, but I have found online versions with both readings of the passage: "Me dijo que tenía a la vista el artículo sobre Uqbar en el volumen XXVI de la Enciclopedia" (Ciudad Seva) and "Me dijo que tenía a la vista el artículo sobre Uqbar, en el volumen XLVI de la Enciclopedia" (Borges todo el año). So a story that hangs, in part, on the instability of a printed text turns out to have fallen prey to the same circumstance.
