Depth of the Ocean. 15 



Challenger sounding, and 3697 fathoms in lat. 21° 53' N., long. 

 65° 0/ W., about 132 nautical miles north of the same sounding. 

 A depth of 3370 fathoms was obtained by the American ship in 

 lat. 25 47' N., long. 65 o' W., which shows that the deepest 

 area in the Atlantic is placed to the northward of the Virgin 

 Islands, and extends over 400 miles along the meridian of 



65° w. 



The greatest depth observed in the Indian Ocean was 

 discovered by the " Gazelle" in May, 1875. Two soundings of 

 3020 and 3010 fathoms were taken in the eastern extremity of 

 this ocean between the north-west coast of Australia and the 

 line of islands extending from Java to Timor. 



The greatest of all depths of which we have reliable evidence 

 was found by the " Challenger" on che 23rd March, 1875, in the 

 comparatively narrow channel which separates the Caroline 

 Islands from the Mariana or Ladrone Islands. This sounding 

 is situated in lat. n° 24 / N., long. 143 16' E., and amounts to 

 4575 fathoms, or about five miles and a quarter. . Several 

 soundings exceeding 4000 fathoms were obtained by the 

 "Tuscarora" to the eastward of the islands of Niphon and 

 Yezo, and another close to the most westerly of the Aleutian 

 Islands. Two of these soundings are over 4600 fathoms, but, 

 as it appears that no sample of the bottom was brought up, there 

 is no evidence of the latter having been reached. H.M.S. 

 " Challenger," shortly after her departure from Yokohama, 

 sounded in 3950 and 3625 fathoms, and in doing so seems to 

 have just touched the southern border of this deep but narrow 

 area of depression, which runs parallel to the eastern coasts of 

 Japan and the Kuril Archipelago as far as the entrance to the 

 Behring Sea (Plate 2). 



It will be observed that the above exceptional depths in the 

 Atlantic, Indian, and Pacific Oceans are not placed, as one 

 might be inclined to conjecture, in or near the centre of these 



