90 A TEXTBOOK OF OCEANOGRAPHY 



continent. Sir James Clark Ross, who discovered a continent 

 soiith of 70° 30' S. Lat. and west of 171° E. Long,, sailed for 

 over 400 miles along an ice barrier, the height of which was 

 estimated to be from 150 to 200 feet. 



Captain Charles Wilkes, of the U.S. Navy, who visited 

 the Antarctic prior to Ross, discovered land and ice barriers 

 between 67° and 64° S. Lat. and 160° and 76° E. Long, in 

 several localities. He averaged the ice-cliffs to be from 150 to 

 250 feet high, and describes icebergs afloat near the barrier as 

 from a quarter of a mile to five miles in length. 



The Antarctic icebergs are tabular in form and often of 

 phénoménal height, 800 feet being by no means unusual, and 

 heights of 1,700 feet are recorded. Thèse bergs are sometimes 

 so large as to receive the name of ice islands. They naturally 

 take longer to melt than the Arctic icebergs. The Arctic bergs 

 seldom last over two years, whereas the larger Antarctic bergs 

 probably last at least ten. 



Between 1891 and 1916 there are six records of Antarctic 

 icebergs of 50 miles length or more ; of thèse, the largest were 

 those reported by the Ethelbert in March, 1893 (82 miles), and 

 by the Antarctic in November, 1894 (70 miles). 



The gênerai northern boundary to which the Antarctic ice- 

 bergs drift is 45° S. Lat. The boundary-lines are bent seawards 

 off the east coast of South America. Icebergs are met with 

 farther north to the eastward of Cape Horn than elsewhere, 

 from Cape Horn (55° W. Long.) right round to 120° E. Long. ; 

 they rarely drift north of 40° S. Lat. From the South Aus- 

 tralian coast in 120° E. Long, round past the Cape of Good 

 Hope to Cape Horn again they drift on the average to 35° 

 S. Lat. (Fig. 15). 



Atmospheric Gases in Sea-Water. 



Water, either fresh or sait, absorbs gases from the 

 atmosphère, and, in fact, sea-water may be considered to hiive 

 atmospheric gas in solution. There are two kinds of solutions. 

 In the one the absorbed gases are liberated by a decrease in 



