It was either very careless or very astute of Nature to leave the entire length of the American continent without a central passage from ocean to ocean, or, having provided such a passage at Nicaragua, to allow it to be obstructed again by volcanic action. This imperviousness of the long American barrier had, as we shall see, important economic and political results, and the eventual opening of a waterway will have results scarcely less important. The Panama Canal will achieve, after more than four centuries, the object with which Columbus spread his sails westwards from the port of Palos--the provision of a sea-route westwards to China and the Indies. The capture of Constantinople in 1453 by the Turks interrupted the ancient trade routes between East and West. Brigands held up the caravans which plodded across the desert sands from the Euphrates and the Indus, and pirates swarmed in the Mediterranean and Red Sea, intercepting the precious cargoes of silks and jewels and spices consigned to the merchants of Italy. The eyes of all Europe were turned to the Atlantic, and an ocean route westwards to India and the Orient, the existence of which had been fabled from the days of Aristotle, became an economic necessity. Columbus, as every one knows, died in the belief that he had discovered this route, and that the lands he had visited were fringes and islands of the Eastern Asiatic continent. The geographers of those days greatly exaggerated the eastern extension of Asia, with the result that the distance from Europe to China and India was underestimated by at least one-half. This was a fortunate mistake, for it is improbable that if Columbus had known that Cathay and Cipangu (Japan) were a good 12,000 miles westwards from the coast of Spain he would have ventured upon a continuous voyage of that length in the vessels of his time.