Tik-Tok of Oz is the eighth book in L. Frank Baum's Oz book series. Baum dedicated the book to Louis F. Gottschalk, friend and composer, who wrote the music for several Baum projects, including the stage version of this story, The Tik-Tok Man of Oz.
A gravity train is a theoretical means of transportation for purposes of commuting between two points on the surface of a sphere, by following a straight tunnel connecting the two points through the interior of the sphere.
I guess you haven’t read the Tik Tok of Oz, which features such a train ride.
nice idea, its a gravity train. not sure it will be built quite yet though.
Thought about this since I was a kid.