Our Geographical Knowledge of the Isthmus—The Value of Early Narratives and Histories—Projects for Uniting the two Oceans by Canals and Railroads—Criteria for Assisting the Judgment—Tunnels, Harbors, Locks, Dimensions of Canal—Tehuantepec—The Garay Grant—Moro’s Survey—Barnard’s Survey—Honduras—A Better Route Practicable—Nicaragua—Louis Napoleon’s Scheme—Col. Childs’ Report—Variations of Route—Advantages of this Line—Chiriqui—St. Clair Morton—No Information Extant—Costa Rica—Railroad Practicable—Great Altitude of Ridge—Panama—Information Abundant—Garella’s Route—Hughes’s Route—Advantages—Cost of Canal on this Route—Mexican Desagues—Panama and Aspinwall—Harbors Easily Improved—Panama Railroad Company—San Blas and Bayano River—F. W. Kelly—McDougal’s Survey—Fine Harbors—Tunnel Seven Miles Long—Darien—Between Caledonia Bay and the Gulf of San Miguel—Baron Humboldt—Vasco Nunez—Paterson’s Colony—Causes of Its Failure—Dr. Cullen and Savana River—Reports the Ridge 150 Feet—English Company—Concessions of the Granadian Government—Mr. Gisborne Sent to Darien—His Speculations—Delayed at Carthagena—Stopped by the Indians—Supposed Success—Misunderstanding with Dr. Cullen—Returns to England—Provisional Directory Organized—Controversy Between Sir Charles Fox and the London Times—Combined Expedition of Four Governments—Lieut. Strain’s Misfortunes—Fails to Find a Pass—Dr. Cullen and Mr. Gisborne’s Failure—Captain Prevost Fails to Cross—Dr. Cullen Changes His Opinion—French Expedition under Bourdiol—Fails to Cross—Granadian Expedition Fails—Condensed Statement of the Results of all the Expeditions—Captains Prevost and Parsons see Evidences of a Pass—Darien Not Yet Explored—San Miguel to the Gulf of Urabá—The Atrato Route—Successful Survey—Representations of Unprofessional Persons—Gorgoza and De La Charme—Their Route—Trautwine —Mr. Porter and Kennish’s Routes—Lieut. Michler’s Route —Extracts from Michler’s Report—Tunnel Two and One-Half Miles—Cost too Small—Barometric—Levels—Humboldt’s Opinion. Having hastily sketched the relation of the proposed canal to the commerce of the world, its importance is sufficiently apparent to justify a careful consideration of the condition of our knowledge of the geography of the Isthmus. The facts and reasoning of previous chapters will furnish a standard, in the absence of a better, for trying the merits of the routes about to be described, and will indicate the nature of the deficiency to be supplied by future explorations.