Action Rockwood, Roy: Five Thousand Miles Underground. v1. 29 Aug 2014

[crutledge]

Roy Rockwood was a house pseudonym used by the Stratemeyer Syndicate for boy's adventure books. The name is most well-remembered for the Bomba the Jungle Boy and Great Marvel series.
Excerpt
Mark and Jack were orphans. After having rather a hard time knocking about the world trying to make a living, they chanced to meet, and resolved to cast their lots together. They boarded a freight train, and, as told in the first volume of this series, entitled, “Through the Air to the North Pole; or the Wonderful Cruise of the Electric Monarch,”the cars were wrecked near where Professor Henderson was building his strange craft.