VERTICAL CIRCULATION. The theory of a ver tical oceanic circulation rests almost entirely upon the study of the thermal conditions existing in the Atlantic. The main facts in support of the theory may be ,111111118rized as follows: (1) The bottom water of every ocean in free com munication with the pole has a temperature but little different from that in polar latitude:: (2) this is true even in the equatorial regions, where the entire mass of the ocean, in case an influx of cold water did not exist, would by virtue of the insoiation attain in the course of time a temperature not lower than 75° F'.; (3) the bot tom temperatures in the case of those oceans to which the cold polar water has free access are somewhat lower than the bottom temperatures where this communication is restricted: (4) the thickness of this bottom of cold water (t;110 fathoms) is too great to admit of the ex planation that it is the return flow of the warm water carried poleward by the drift surface cur rents; (5) there is a continual ascent of glacial water under the line, shown by the moderation of the surface temperatures along the equator, also by the fact that polar temperatures are here attained at less depth than in somewhat higher latitudes; (6) On the basis of this hypo thesis the presence of the cold band along the eastern mast of North America can be explained as the ascent toward the surface of the polar water, diverted from its original equatorial course by the effect of the earth's rotation, and forced up the Atlantic slope.
Blum°Gam-uv. Cron, On the Physical Cause of Ocean Currrnts (London, 1874) ; Ferrell, "The lotion of Fluids and Solid: on the Earth's Sur face." in United Status tEtignal Serriee Profes sional Paws, No, S (Washington, riSS:2) ; Zur Erchanik der Ileeresstriimungca (Berlin, 1884) ; Engelhardt, L'ntersuchungen iibcr die Strtimungen der Ostsee (Alton:), Page, ('urrents." in \utionuf Geogrophie ihyrt:ifle (Washington, 1902). See ATLAN TIC ( )CEAN ; PACIFIC OCEAN; 1NOIAN ( )(EAN ; GULF STREAM, etc.