These formerly elevated points were simply projections upon two orogenic blocks of the earth’s crust, one extending from South America to Porto Rico, the other the narrower coastal shelf forming the isthmus. More plainly, these remarkable strips, curved in outline, and with a varying length of four hundred to five hundred miles, maintained a precarious stability with references to the adjoining edges against which they abutted, and when a shock, violent enough to rupture or release those edges, supervened they fell _out_ and _down_ like a brick or stone from an arch. When the more eastern of these blocks, that on which the lesser Antilles stood, dropped, the oceanic heated currents of the equatorial belt of the Atlantic rushed into the Caribbean basin as usual, but with a perceptible acceleration. The currents did not meet the frictional resistance of an archipelago of small islands. Their progress westward continued, through the almost simultaneously created outlet into the Pacific, by the submergence of the isthmus. Upon the first report of President Roosevelt’s apprehensions that this catastrophe would involve a disastrous diversion of the Gulf Stream, European geographers had contemptuously treated it as impossible, and stigmatized it as “an amusing futility of envy.” They dwelt upon this fact, that the Gulf Stream did not invade the bent arm of water forming the eastern water boundary of the Isthmus of Panama, but shot across this somewhat withdrawn angle, passing with undiminished volume in a straight path beyond Honduras, into the capacious pocket of the Gulf of Mexico. “Let it be conceded,” began an authoritative refutation in the _London Times_, “that the structural impediment to the mixture of the waters of the Atlantic and Pacific existing in the Isthmus of Panama is removed. Does mixture follow? By no means, that is in no way subversive of present hydrographic conditions. There will be a marginal intermixture, of course, where there is actual contact, but it is presumptuous and opposed to experience to say that two enormous bodies of water will promiscuously exchange their contents through an opening, relatively to their volume and extent, what a pinhole would be to the juxtaposed masses of two great reservoirs. Further, this _disinclination_, as a physical impossibility, of the waters of the two contiguous bodies of practically equal density to diffuse into each other, is increased by the strength and velocity of the Gulf Stream itself, which rushes past the isthmus deflection, and instead of being turned aside into that narrow aperture, would exert a suctorial influence upon the tides of the Pacific, actually (though this is in no way insisted upon) reinforcing its own volume and momentum by their contributions.