The Smoky God: A Voyage to the Inner World 

When Olaf Jenson discovers a secret hidden world within the bowels of the earth, he has no idea that it will be as hard to leave as it was to find it. This subterranean, Edenic civilization is inhabited by a race of scientifically advanced giants who worship the “smoky God” in the center of the earth.

This novel brought acclaim to its author, Willis George Emerson, when it was first published in 1908. It is an example of early 20th century science fiction.