i84 



PRINCIPLES OF STRATIGRAPHY 



fathoms (915 meters) or more, after which the rate of decrease 

 becomes a slower one. Thus the Challenger Expedition found at 

 one of its stations in the South Atlantic (35° 59' S., 1° 34' E.) a 

 drop from 13.4° to 13.0° in the first 100 fathoms, i. e., a decrease of 

 only 0.4° then a rapid drop to about 4.5° C. at 400 fathoms, or a de- 

 crease of about 8.5° in 300 fathoms, after which the decrease was 

 a slow one again to nearly 2° at 1,500 fathoms, or 6.5° in 1,100 

 fathoms (Fig. 26). In general, the temperature of the deeper 



!♦"€ 



1500F 

 2745 m. 



Fig. 26. Diagram illustrating the rate of decrease of temperature from the 

 surface to 1,500 fathoms. Challenger station, South Atlantic, 

 35° 58' S. 1° 34' E. (After Kriimmel.) 



parts of the oceans becomes relatively uniform below 1,000 meters, 

 so that where the average depth is 4.000 m. only the upper 34 ^s 

 affected. The other y^ of the ocean are generally below 3° C, 

 and near the bottom the temperature, even in many parts of the 

 tropics, is but little above 0° C. 



Temperature of the Sea. 



Horizontal axd Vertical Distribution of the Temperature 

 IN THE Three Great Oceans. Leaving the Arctic Ocean for sep- 



