Welcomed with the approving plaudits of his king and countrymen, or loaded with ignominious chains, he had ever kept one object constantly in view. This object, pursued with unexampled courage, self-abnegation, and constancy, he was now called on to renounce. Who will venture to depict the thoughts of this remarkable man as he turned to retrace his path, leaving behind him the prospect of discoveries far greater than those which had cast the hallow of immortal fame around his name? “Here ended,” says Irving, in a strain of tender eloquence, “the lofty aspirations which had elevated him above all mercenary views in his struggle along this perilous coast”——“it is true, he had been in pursuit of a chimera, but it was the chimera of a splendid imagination and a penetrating judgment. If he was disappointed in finding a strait through the Isthmus of Darien, it was because Nature herself was disappointed.” This sagacious conjecture has its foundation in nature, and is supported by the opinions of savans and the facts of recent geological explorations. The Prussian geographer, Berghaus, as early as 1823, and Prof. Hopkins, contested the accepted opinion as to the unbroken continuity of the Isthmus and the contiguous continents. The French engineer, Garella, after making a geological reconnoissance, declares that the Isthmus is of more recent origin than the continents which it unites. Col. Hughes and Garella concur in a belief in the existence, at an early period, of a strait uniting the Atlantic and Pacific oceans. The identity of the species of fish inhabiting the waters on both sides of the Isthmus is an additional argument in confirmation of this view. It is without surprise that we find the discoveries of another science confirming this inference. Prof. Huxley, in a recent address on the progress of palæontology, is unable to explain the distribution of mammals at the close of the miocene period, except upon the supposition of a barrier which prevented the migration of the apes, rodents, and edentata from the southern to the northern continent. He cites the opinions of Carrick Moore and Prof. Duncan in support of the same conclusion. Further investigation will, no doubt, add to the number of facts which indicate the separation of the two continents by the ancient sea, and may even establish the fact that portions of Central America once formed parts of the Antilles group of the equatorial belt of islands.