. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature. is not a little remarkable that the sub-surface stratumot water, having a temperature above 40°, is thinner underthe equator than it is in any other part of the Atknticfrom the Faroe Islands to the Cape of Good Hope. Not-withstanding the rise of the surface-temperature to 76°-80°,tlie thermometer descends in the first 300 fathoms morerapidly than anywhere else; so that polar water is metwith, as shown in fig. 3, at a much less depth than in the North Atlantic (fig. 1), and 100 fathoms nearer to thesurfac
. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature. is not a little remarkable that the sub-surface stratumot water, having a temperature above 40°, is thinner underthe equator than it is in any other part of the Atknticfrom the Faroe Islands to the Cape of Good Hope. Not-withstanding the rise of the surface-temperature to 76°-80°,tlie thermometer descends in the first 300 fathoms morerapidly than anywhere else; so that polar water is metwith, as shown in fig. 3, at a much less depth than in the North Atlantic (fig. 1), and 100 fathoms nearer to thesurface than even in the colder South Atlantic (fig. 2);whilst the temperature of the bottom is but little above32°. Thus the influence of the polar underflow is morepronounced under the equator than it is elsewhere ; as isdistinctly seen in the section shown in fig. 4, which istaken in a north and south direction so as to exhibit therelation of the thermal stratification of the North to that 24 ATLANTIC of the South Atlantic, and of both to that of the equatorial I EOU/STOBIAL belt. Fia. 3.—Section of Equatoiiul AtlanticThe isotherm of 40°, which in lat. 22° N. lies at a depth of about 700 fathoms, gradually rises as the equatoris approached ; and it is between the equator and 7° S.,where the surface-temperature rises to nearly 80°, that coldwater is soonest reached,—the isotherm of 40° rising towithin 300 fathoms of the surface, while that of 55°, wliirhin lat. 38° N. lies at nearly 400 fathoms depth, and iu lat22° N. at about 250 fathoms, actually comes up under theequator within 100 fathoms of the surface. At the saiuetime, while the bottom-temperature under the equator is tlielowest anywhere met with, namely, 32°4, the thickness ofthe stratum beneath the isotherm of 35° is not less thanGOO fathoms. In passing southwards, the superficial iso-therms are observed to separate again from each other,partly by the reduction of the surface-temperature, andpar
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