“It was pointed out by Prof. Robert T. Hill that the current, and formerly undisputed, conception that the Rocky Mountains of North America and the Andes of South America were not only analogous physiographically, but univalent in fact; that the continuous elevation of Central America brought them into an oblique alignment; and that their mutual prolongations met in the Isthmus of Panama, was erroneous. It involved a complete misconception. It was a geographical fallacy, and leads to misleading conclusions as to the permanency of this intermedian region, itself pre-eminently individualized and liberated from the circumstances and implications of either the Rocky Mountain Continent or the Andean Continent. This area has a different geological ancestry. To-day it invokes an especial treatment, and possibly expects a future, contrasted with that of the two great Continents whose longitudinal extension it contravenes by its east and west lines, by the prerogatives of a separate origin.
“The Rocky Mountains terminate in the plateau of Mexico, ‘a little south,’ says Hill, ‘of the capital of that republic; and that the mountains have no orographic continuity, or other features in common with those of the Central American region.’
“And the same authority, describing the terminus of the Andes, says, ‘The northern end of the Andean System lies entirely east of the Central American region, and is separated from it by the Rio Atrato—the most western of the great Rivers of Columbia. In fact, the deeply eroded drainage valley of this stream nearly severs the Pacific coast from the republic of Columbia, and the isthmian region, from the South American continent.’
“The Central American volcanoes belong to the type that is repeated along the Caribbean shores of Colombia and Venezuela, and those in the Isthmus of Panama, and those of the great Antilles. The genesis of this American Mediterranean land-aggregate was in an independent geological impulse, and the land aggregate itself impinged by intersection upon the dominant land surfaces of North and South America. To bring together North and South America as a simultaneous geological phenomena is wrong, to make them other than an accidental geographical continuity questionable. It is this intermediate zone—the Antillean continent with lateral elongations, grasping within its continental solidarity the parallel zones of Central America and the Isthmus, that gives them terrestrial unity. Extend the axis of the Rocky Mountains, and it passes almost two thousand miles west of the coast of South America; extend the axis of the Andes and it bisects the western extremity of Cuba, and passes along the seaboard of the United States.
“There is no exact geological identity here, although there is the strictest geographical homology. Each is the backbone of a continent, each upheaved and variously modified, igneously invaded sediments, derived from some pre-existent continent. They may be brought into a just comparison, but they are not strictly parts of one phenomenon. They are, however, more closely related to each other, than the Antillean areas are to either. This Antillean area, I shall here call the Columbian Continent, as the great discoverer landed at its two east and west extremities—the land-fall on San Salvador in the Bermudas, and on the coast of Honduras in Central America, as well as at Cuba, and at the mouths of the Orinoco—and his bones rested for a long time in the soil of San Domingo. It—this Columbean Continent—is a significant intercalation. It unites North and South America, but it unites them subject to the phases of its own generation.
“Let us understand this. There is a system of growth, a law, if I may so term it, of geomorphic sameness in the development of large, or for that matter, small geological territories. The familiar story of the growth of our North American continent has been often told. It is a commonplace of text books. The wide, triangular Archæan nucleus to the north, the oldest rocks—outlines and outliers down the east, and the same in the west—drew the framing limits of the continent at the first, to be filled in, up and out, by the momentous additions through the ages of advancing time. In Europe less well or simply defined boundaries, the growth together rather of divided islands, prevailed, and the picture of development was quite varied, from the picture in this western world. Again in Africa, with edges of uplift and centres of depression another geological tale with its incidents and accessories infinitely modified, comes into view. And in this prevalence of structural style, we, geologically speaking, find a prevalence of certain geological phases or conditions.
“What were these in the growth and disappearance of this Columbian continent? What they have been, we can, with rational probability, assume they will be.
“The Columbian continent, I have called a dismembered, a fractionized continent. If from Cuba through Haiti, Porto Rico, and the lesser Antilles one land surface obtained, and the now submerged and radiating gorges, found only as submarine canyons, were above the ocean, becoming, as Prof. Spencer has laboriously proven, sub-aerial river valleys, we should have one presumable phase of this continent, the phase of its maximum cohesion and extension. And such a phase is measurably or, for purposes of argumentative inference, sensibly established. It is said with careful premeditation by Hill that ‘the numerous islets of its eastern border, the Bahamas and Windward chain, which extend from Florida to the mouth of the Orinoco, are merely the summits of steep submarine ridges, which divide the depths of the Atlantic from those of the Gulf of Mexico, and Caribbean sea; were their waters a few feet lower, these ridges would completely landlock the seas from the ocean.’
“When thus constituted, it afforded a display of physical features of astonishing contrasts, and its mere scenic resources were doubtless of unparalleled splendor, and, as to-day, it was involved in the luxuriant productivity of the tropics. Its mountains measuring now as high as eleven thousand feet above the sea level, were then thrust upward into stupendous peaks, by the addition of the sloping miles which are now below the ocean. We can imagine the extreme wonderfulness of this continent, uniting in an unbroken but marvellously varied expression of physical and vegetable contrast, the plains, valleys, and mountains of Cuba, the towering and draped peaks of Jamaica, the confusion of the gloomy vales and ranges of Hayti and San Domingo, the levels and coastal ranges of Porto Rico, and the manifold picturesque charms of the Lesser Antilles, lifting high into the ceaseless currents of the trade winds the smoking summits of a chain of disturbed volcanoes. All, in the boundless abundance of its natural endowment of loveliness, and productivity, formed an unique and extravagantly ornamented landscape, an area whose highest elevations contemplated the remote waters of the shrunk Atlantic, from pinnacles raised ten to twenty thousand feet above its azure waves. Nor is this all. This hypothetical—the Columbian—continent, may have had connexions with Central America through projecting and peninsulated capes, reaching through Jamaica to Yucatan or Honduras, and wide intervals of dividing gulfs of water, in all probability sundered it from North or South America, and it remained, as I here emphatically insist, it remains to-day, a geographical and geological phenomenon, unrelated to the great continents, to which through their preponderating value, the mind almost unpremeditatingly assigns it.
“But at the period of this greatest elevation, when this tropical region assumed individual independence, and embodied a geognostic importance comparable to the vast continents it lay between—at this time—the Isthmus of Panama did not exist, and through a wide water-way the Atlantic mingled its tides with those of the Pacific.