William Reed

And this is mentioned in passing in a conversation between, I think it's Crozier and Fitzjames.

But William Reid is the author of a book called The Phantom of the Poles, published in 1906.

And the author reads book posits all kinds of evidence for the hollow earth based on scientific observations in the Arctic regions.

I read this years ago from an online facsimile by John Bruno Hare uploaded in 2005, which I can no longer see anywhere online.

Put that in the show notes as well.

Lastly, I want to mention Dan Simmons' own acknowledgements, which are extensive.

He doesn't mention William Reid, but the historical sources are numerous and diverse, and cover the Franklin Expedition, including a real letter from Harry Goodser, and various historical texts, as well as accounts of polar expeditions, Inuit myth, and the like, which are, well, extensive.

Apparently, the book was kicked off by a footnote about the Franklin Expedition in Sir Ranulph Fine's book Race to the Pole.