Release Message:  Large immobile masses of iron in the earth's crust enable two-way travel between two points in the planet's history. Written by Murray Leinster.

Description:  Large immobile masses of iron in the earth's crust enable two-way travel between two points in the planet's history. The Time Tunnel. One end was in 1964 -- the other in 1804. People could go both ways. So could... things. For instance, brand new antiques for the 20th Century, and marvels of modern industry for the Napoleonic era. But you had to be careful -- because what would happen to now if you did something in 1804 that changed history? It was unthinkable. Unfortunately, it happened.... Predates the series, and the subsequent two novels based on the show.