Murdoch re-engineers a simplified version of the seismograph which he admits had been previously invented.
The episode's title refers to "Journey to the Center of the Earth" ((French: Voyage au centre de la Terre), a novel by French author Jules Verne, first published in 1864. It is part of a sequence of 54 novels called the "Voyages extraordinaires" (meaning "Extraordinary Voyages" or "Amazing Journeys").
Actress Lauren Lee Smith would later meet Constable George Crabtree, as Frankie Drake in the series Frankie Drake Mysteries, Season 1, Episode 8.
This episode takes place in 1901.