Transmission theory: what the heck was Tolkien thinking?

[Kuruharan]

Originally Posted by William Cloud Hicklin

(Incidentally, this would not be the first time Tolkien entertained two contradictory ideas simultaneously- for a while in the writing of Book V, he seemingly had Frodo look out at the moon over the Forbidden Pool at the same time as Pippin aboard Shadowfax *and* Pippin on the battlements of Minas Tirith!)

I suspect that this is the answer to the riddle right here...unless the records Bilbo worked from were saved archives from Arnor, which I suppose is possible.

Still, he was right there in Rivendell for the entire latter part of his life on Middle earth with, presumably, plenty of elvish records right there to hand...