The Rivers and Beacon-hills of Gondor
This essay has never been published in its entirety, although parts of it were published in Unfinished Tales, and the remaining parts were published in the periodical Vinyar Tengwar, issue number 42 in 2001. The Vinyar Tengwar article was based on a version intended for publication by Christopher Tolkien in The Peoples of Middle-earth but was not included due to space constraints, although it is mentioned in the book.
According to Christopher Tolkien, the essay's germ was a letter by Paul Bibire to Tolkien on 23 June, 1969 inquiring whether the river Glanduin is the same as that of the Swanfleet. Tolkien replied on 30 June (in the letter Letter to Paul Bibire), stating that the Swanfleet is the same river as the Glanduin, although the former is applied to the upper course of the river. It is from the answer of this query that Tolkien decided to embark on a comprehensive essay of not only the Rivers of Gondor, but also of the Beacon-hills of Gondor, as mentioned in The Return of the King.
However, like many of his late works, Tolkien never got to finish the essay, abandoning it while in the middle of the discussion of the beacon-hill Halifirien. However, based on what can be gleaned from this, it seems it is at this point that Tolkien decided to introduce the idea of having the tomb of Elendil in Halifirien, which became an essential element in the work Cirion and Eorl. Therefore from Paul Bibire's query arose the history of Halifirien and Elendil's tomb.
The essay is likewise notable for presenting a discussion of the Eldarin numerals.