Impossibilities have been accomplished, poetical fictions have become facts, visionary theories of the past are the industrial arts of the present. In wealth, comfort, health, longevity, art, science, organized labor and charities, the human race of the present have out-stripped the Arcadian felicity of the golden eras of Hesiod and Cervantes. Possessing every facility, occupying a preëminent coigne of vantage, we have left one thing unachieved. This ought we to have done, and not to have left the others undone. Many minds, speculative and practical, have closely scrutinized the feasibility of making the American Isthmus a highway for the commerce of the world. Its importance grows in dimensions in proportion to the study bestowed on it. It ranks among its friends some of the most able men of the race. Columbus, Cortes, Charles V, Alverado, Gonzales de Avila, De Solis, Gomaro, Bautista Antonella, and, in more recent times, Paterson, Pitt, Jefferson, Humboldt, Guizot, Napoleon III, Wheaton, Dallas, Biddle, and a long and honorable list of statesmen and publicists have contributed to the project. According to the scheme of General Miranda, sanctioned by Wm. Pitt, it was proposed that Great Britain should supply the money and ships, and the United States should send 10,000 men. The failure of this plan is attributed to delay on the part of President Adams. The tonnage of the trade which would annually seek this route has been estimated at 3,094,000 tons, equal in value to $152,475,750. The value of the exports and imports of all the nations which would annually pass the Isthmus would amount to $451,029,132. With such enormous commercial interests, backed by advocates so able, it is not a little curious that the question of feasibility should be yet unsolved. Political vicissitudes have often postponed its consideration. Conflicting interest and rivalries have prevented the coöperation long deemed essential to its successful execution. The hereditary policy of the United States has always been anti-social and insular. Schooled in this policy, it is difficult to enlist the sympathies of our people in questions which are to be answered in regions beyond their jurisdiction. The utility and practicability of the work must first be made clearly manifest. Passing in review the present state of our knowledge of Isthmean routes, one of the objects of this paper is to attempt to appreciate the probable advantages which would result from the completion of an intermarine ship canal. In selecting from material, much of which bears little relation to the questions at issue, many objects may be omitted which deserve notice, and some may be noticed which might have been omitted. If serious attention is attracted to this important project, the writer will have attained his object.