i86 PRINCIPLES OF STRATIGRAPHY 



surface are shown by the isobars of February and August on tem- 

 perature maps. At a depth of lOO meters the surface influence 

 is still visible to some extent. The Indian and West Pacific 

 are strongly contrasted with the Atlantic. The zone of tem- 

 peratures exceeding 25° C. comprises the West Pacific, west of 

 125° W. long, and between 18° N. and S. lat., and continues 

 through the Banda and Flores seas into the Indian, extending north- 

 westward to Ceylon, and westward beyond the Maldives (to 65° E. 

 long). In the Atlantic, on the other hand, only a small area in the 

 Brazilian current reaches this mean temperature. Along the whole 

 western border of tropical America, as well as tropical Africa, the 

 temperature of the water does not rise above 20° C. at a depth of 

 100 meters, though higher temperatures exist at the surface. No 

 temperatures of 0° are known at a depth of 100 meters in the 

 North Atlantic or North Pacific, except at the south end of Green- 

 land and in Denmark and Davis Straits and close to the southeast 

 coast of Kamtchatka, where the cold currents enter from the Arc- 

 tic. In Davis Straits, near the Arctic circle, the surface tempera- 

 ture varies from 4-i-i5° C. to -(-2.6° C, whereas in Denmark 

 Straits the surface temperature as well as that at 100 meters is 

 —0.7° C, but at 50 meters it is —1.5° C, rising to +1.5° C. at 150 

 m. and to -|- 3-i° C. at 200 m. At a depth of 200 meters the tempera- 

 ture distribution becomes greatly modified, the chief feature being 

 the distribution of the warmer portions of this stratum in the three 

 great oceans, which, instead of lying in the equatorial region, are 

 now pushed to the north and south of the same, an arrangement 

 which becomes still more pronounced at a depth of 400 meters. At 

 this depth the zone of highest temperature, over 18° C, lies in the 

 West Atlantic below the Florida stream, at about 30° N. lat. Be- 

 tween 22° and 40° N. lat. the temperature at this depth is every- 

 where above 17° C. in the western half of the North Atlantic. In 

 the South Pacific a temperature of 16° was found only near the 

 Fiji Islands at this depth, 14° or even 12° being the more usual 

 maximum temperature. At a depth of 600 meters the area of 

 maximum temperatures in the North Atlantic spreads eastward 

 (between 20° and 40° N. lat.) and shows a height of over 10°, in- 

 creasing in some cases to 16.8° (northwest of the Bermudas), while 

 under the equator the temperatures are only 5° or 5.5°. Maximum 

 temperatures of over 10° C. are found besides in the South Pa- 

 cific in scattered areas, and in the Indian Ocean at this depth. At 

 1,000 meters the mid North Atlantic is bounded by the 7° isotherm, 

 which is deflected northward to the North British coast. Tempera- 

 tures of 8° occur in two areas, between 30° and 40° N. lat. and 40° 



