Geography of the Sea. 149 



slowly to the bottom. In the equatorial calm regions, however, 

 where the heavy rains dilute the surface water, the density de- 

 creases from the surface down to between 50 and 100 fathoms, 

 after which it follows the law found for other parts of the ocean. 

 The bottom densities of the South Atlantic and Pacific have been 

 found about alike, varying only from 1.02570 to 1.02590 ; those 

 of the North Atlantic, however, show a greater value, varying 

 from 1.02616 to 1.02632. 



Greatest Depths of the Oceans. 



Atlantic. — Rejecting some of the earliest soundings as un- 

 trustworthy, the greatest known depth in the North Atlantic is 

 to the north of the island of Puerto Rico, in about latitude 

 19° 39' K, longitude 66° 26' W., found by the C. S. S. Blake, 

 Lieut. Commander Brownson, U. S. isL^in 1882-83, 4,561 fath- 

 oms. 



The deepest known spot in the South Atlantic is 3,284 fathoms, 

 in about latitude 19° 55' S., longitude 24° 50' W., sounded by the 

 U. S. S, Essex, Commander Schley, in 1878. 



The general run of the soundings indicates that greater depres- 

 sions exist nearer the western than in the eastern or middle part 

 of the Atlantic, North and South. 



Pacific. — In the North Pacific the greatest depression has 

 been found by the U. S. S. Tuscarora, Commander Geo. E. Bel- 

 knap, TJ. S. N., in 1874, 4,655 fathoms, in latitude 44° 55' N., 

 longitude 152° 26' E. The next deepest sounding in the North 

 Pacific was located by the Challenger in 1875, 4,475 fathoms, 

 in latitude 11° 24' N., longitude 143° 16' E. As in the Atlantic, 

 the greater depths appear to exist in the western part and par- 

 ticularly off the coasts of Japan, 



In the South Pacific the greatest depths were supposed, up to 

 a recent period, to be in the eastern part. Within the last two 

 years, however, the British surveying vessel Egeria has discovered 

 greater depressions in the western part of the South Pacific, one 

 spot sounding 4,430 fathoms in latitude 24" 37' S., longitude 175° 

 08' W., and another, 12 miles farther south, 4,298 fathoms. 



Indian Ocean. — In this ocean the greatest depths appear to 

 exist to the north and west of the Australian continent, where 

 there are more than 3,000 fathoms in a number of widely sepa- 

 rated spots, indicating a depressed area of considerable extent. 



In the most southerly part of the Indian Ocean, or rather in the 



