THE ABYSSAL REGION OF THE SEA. 13 



other things it has enabled some idea to be formed 

 as to the area of this region (now known as " The 

 Abyssal Region " of the ocean), which is estimated at 

 " about one hundred millions of square miles. " It is 

 also now ascertained that this enormous area, consider- 

 ably exceeding the whole surface of the terrestrial 

 globe in extent, lies at a mean " depth of 2500 fathoms 

 beneath the surface of the sea. " * 



Of course it will be understood, that when 2500 

 fathoms or nearly three statute miles (2640 fathoms = 

 3 miles statute measure) is given as the average depth 

 of this great region, its greatest depths are very much 

 greater still. 



The deepest sounding obtained by the Challenger 

 expedition in the Atlantic Ocean, " being one taken 

 about 100 miles north from the island of St. Thomas, 

 which was 3875 fathoms" (or 4 miles 710 yards) f in 

 other words 23,250 feet, or as near as possible the 

 height of the summit of the Aconcagua in Chili, the 

 highest mountain on the continent of America. 



This great depth was however eclipsed by the results 

 obtained in the Pacific Ocean, where, "in 1875 when 

 sounding the channel between the Carolines and the 

 Ladrones islands, the Challenger met with the deepest 

 water of the cruise, 4475 fathoms" (or upwards of 4^- 

 miles) " and this is the greatest depth from which a 

 specimen of the bottom has hitherto been obtained. " 



* See page 46 of the Introduction to the Report on the Scientific 

 Reszdts of the Voyage of H.M.S. Challenger, Vol. i., 1880, Edited 

 by Sir C. Wyville Thomson, F.R.S., Regius Professor of Natural 

 History at Edinburgh University. 



f In Lat. 19 41' o'' N., Lo'ng. 65 7' o" W. Soundings N 72., Ibid., 

 Vol. i., p. 52. 



EncycL Brit., gth edit., Vol. xviii., p. 121 (Article " Pacific Ocean "). 



N.B. This sounding represents a depth of 26,850 feet, or 5 miles 

 150 yards; this however is still inferior to the elevation of some of the 



