114 THE ICE AGE IS NORTH AMERICA. 



feet above the sea-level, 1.000 leer chick, and 450 miles in 

 length." 



A similar vertical wall of ice was seen by DTrville. off the 

 coast of Adelie Laud. He thus describes it : " Its appearance 



was astonishing. We perceived a cliif having a uniform eleva- 

 tion of from 100 to 150 feet, forming a long line extending orf 

 to the west . . . Thus for more than twelve hours we had 

 followed this wall of ice. and found its sides everywhere per- 

 fectly vertical and its summit horizontal. Not the smallest 

 irregularity, not the most inconsiderable elevation, broke its 

 uniformity, for the twenty leagues of distance which we fol- 

 lowed it during the day. although we passed it occasionally at 

 a distance of only two or three miles, so that we could make 

 out with ease its smallest irregularities. Some large pieces of 

 ice were lying along the side of this frozen coast ; but, on the 

 whole, there was open sea in the offing. 



* 



In addition to the recent direct observations upon the 

 glaciers of the Antarctic Continent, we are permitted to 

 turn to an important source of indirect evidence furnished 

 by the icebergs encountered in the region. Many of these 

 are of such >ize as to indicate an enormous depth to the glacial 

 ice of which they are fragments, and imply the existence of 

 a glaciated area larger even than Greenland. In reading the 

 accounts of icebergs we should bear in mind that the specific 

 gravity of ice is such that where there is one cubic foot of 

 an iceberg above the water's surface there are seven or eight 

 cubic feet below the surface ; so that, if the form of the berg 

 could be supposed to be symmetrical, we should multiply 

 the height of the berg above water by eight or nine to get 

 its perpendicular dimension. But as the forms of the ice- 

 bergs are usually irregular, this rule can not always be ap- 

 plied. In several of the instances to be referred to. however, 

 the masses are so large, and the forms so regular, that we 

 can not be far amiss in applying the rule. Some of these 

 masses of rloatino; ice are of almost incredible size, and their 



* Quoted by Whitney in " Climatic Changes,*' pp. 315, 316. 



