of its nearly level floor, which is from 2,035 to 2,071 fathoms below sea-level. (On Fig. 3 only the general depths of these great depressions are indicated.) Coupled with the profound depth of the sea in the West Indian region are the rugged mountains of the Great Antilles and the volcanic cones of the Caribbees. Some of the elevations of the land referred to are, in feet, as follows: Porto Rico, 3,609; Jamaica, 7,360; Cuba, 8,600; and Santo Domingo, 10,300. The extreme range in the relief of the surface of the solid earth (lithosphere) between the bottom of Brownson Deep and the summit of Santo Domingo is 37,666 feet—the horizontal distance between the two is about 270 geographical miles. No mountain on the earth has such an elevation above sea-level. The islands of the West Indies are thus shown to be the summits of stupendous mountains, the greater portions of which are submerged. The low-lying islands, and even the banks which can be discovered only with the aid of the sounding-line, are in reality the tops of wonderfully steep mountains or plateaus some 20,000 feet in height.
It is a significant fact that the profiles of the partially or wholly submerged mountains of the West Indies are, as a rule, steeper than the slopes of the mountains on the land with which they may reasonably be compared. This is due in part, perhaps, to the greater density of the medium in which they stand, the sea-water affording a greater degree of support than the air, but the main reason is that beneath a few hundred feet of water there is no erosion except the exceedingly slow removal of matter in solution. Could the waters of the sea be withdrawn so as to reveal the Caribbean Mountains in all of their stupendous grandeur, the vast, smooth, sweeping surfaces extending from the horizontal lines drawn about the higher summits by the waves and by the deposition of sediment and coral growths, down to their bases would be unmarked by channels and ridges of the character that give details to the type of mountains with which we are most familiar.
An instructive generalization concerning the relief of the West India region, suggested by Alexander Agassiz
and sustained by the later studies of R. T. Hill, is that we there find topographic forms produced by movements in the earth's crust which have not been modified by erosion. The great elevations rising from the floors of the "deeps" are upraised blocks of the earth's crust which have not been beaten by rain, shattered by frost, or trenched by rills, creeks, or rivers. They illustrate the character of the rough blocks of rock from which many of the mountain forms of the land have been sculptured.
This sweeping view, which it seems safe to accept as a generalized outline of the history of the topography of the region in question, needs to be qualified, as there are known to have been extensive up and down movements throughout large areas in that portion of the earth's surface. The mountains on Jamaica are scored by horizontal lines marking former sea-levels up to a height of 2,000 feet, and similar and still higher records are plainly visible on several of the larger West India islands. This evidence shows that the present land over a wide extent of the Caribbean region was formerly deeply submerged. More than this, the rocks forming the higher portions of the Greater Antilles are largely composed of more or less consolidated ooze, such as is now found on the sea-floor in deep water. This line of evidence shows that what in late geological time was the sea-floor has been raised between 20,000 and 30,000 feet. It is thus known that both upward and downward movements of great vertical and great horizontal extent have occurred in the Caribbean region. Whatever minor changes the topography of the now submerged sea-floor may have suffered owing to emergence, the general relief, as suggested above, seems to have resulted from movements in the earth's crust, and that these movements, in certain instances at least, produced faults—that is, breaks or fissures—along which the rocks were upraised on one side or depressed on the other, so as to form great cliffs. The precipitous submarine slope forming the northwest border of Bartlett Deep may reasonably be interpreted as a great fault scarp. A portion of this escarpment rises above the sea and forms the remarkably straight and exceedingly
rugged south coast of Cuba in the region of Santiago. In the main the remarkable submarine topography of the West India region presents us with an example of what would have been the leading features of several portions of the earth's surface which are now land, as, for example, the Great Basin region of Utah, Nevada, etc., had deformation gone on without erosion.
MOVEMENTS OF THE OCEAN WATERS
To the student of the geography of a continent the climatic and other influences of the great ocean currents, as well as the more tangible results produced by the waves which break on the borders of the land, demand extended and painstaking investigation. The most that we can hope to do at present in this connection is to state briefly some of the more important influences that the movements of the ocean waters have on the climate of North America and on the topography of its shores.
Currents.—The surface waters of both the north Atlantic and the north Pacific, as is the case with all broad water bodies, have a drift and in places flow in well-defined currents, mainly on account of the friction of the wind on the surface of the sea, aided by variations in the density of the water due to differences in temperature and salinity. In each ocean there is a great swirl or eddy, for the reason that the surface drift and the flow of the deeper currents carry the waters about in a rudely circular path, parallel in a general way with the boundaries of the respective basins. The direction of this motion, to one situated in the central part of either basin, is from left to right, or with the movements of the hands of a watch. In the southern portion of each basin there is a westward-flowing equatorial current, which in each instance is deflected northward on approaching the bordering land, and as it continues is still more deflected owing to the influence of the earth's rotation, and acquires a northeast trend; on reaching the eastern side of the oceanic basins, the currents are again deflected, a portion of the one in the Atlantic and all of the one in
the Pacific being turned southward so as to complete the circuit.