“Precisely such catastrophes are discovered in the history of the geological region now before us. The islands of the West Indies have been subjected to great changes of elevation. They have risen and fallen during the last geological age--the Tertiary--perhaps four times. In their rise they have gathered to themselves marginal extensions of land, now hidden beneath the ocean at comparatively slight depths, while they have at the same time doubtless become blended and unified into a great Antillean continent. This continent was dominated by volcanic protuberances whose growth upward, over accumulations of ashes, has been again symptomatic of undermining operations threatening later subsidence and submergence. “In our day we have been called on to deplore the ravages caused by the eruptions of Mt. Pelee and La Soufriere, on the Islands of Martinique and St. Vincent, and it is natural to insist that regions which have a precarious autonomy, in which such volcanoes can exist, must be regarded with diffidence, as permanent geographical areas. “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.’