Book 1, Chapter 1 Summary and Analysis

"Threshold" examines early interest in joining the Atlantic and Pacific oceans somewhere in Central America, concentrating on U.S. expeditions through 1875. There are at least 19 points narrow enough for a canal. On Jan. 10, 1870, Navy Secretary George M. Robeson orders Cdr. Thomas O. Selfridge to the Isthmus of Darien at Caledonia Bay, 150 miles east of the Panama Canal Railroad, to gather botanical and geological specimens, take astronomical observations, and report on the climate and the natives. Plans call for six more expeditions, whose cumulative results the Interoceanic Canal Commission (ICC) will appraise.

The Navy remembers 1850, when Lt. Isaac Strain's party nearly perishes trying to find a path at Darien, which Dr. Edward Cullen has claimed to find. Adm. Daniel Ammen, chief of the Bureau of Navigation, finds in the Strain Report evidence of a low-lying valley running inland. Interest is...