EXISTING GLACIERS. 17 



covered with morainic detritus." The Mueller Glacier is 

 about seven miles long and one mile broad in its lower 

 portion. 



South America. — In America, existing glaciers are 

 chiefly confined to three principal centres, namely, to 

 the Andes, south of the equator ; to the Cordilleras, north 

 of central California ; and to Greenland. 



In South America, however, the high mountains of 

 Ecuador sustain a few glaciers above the twelve-thousand- 

 foot level. The largest of these are upon the eastern slope 

 of the mountains, giving rise to some of the branches of 

 the Amazon — indeed, on the flanks of Cotopaxi, Chimbo- 

 razo, and Illinissa there are some glaciers in close proximity 

 to the equator which are fairly comparable in size to those 

 of the Alps. 



In Chili, at about latitude 35°, glaciers begin to ap- 

 pear at lower levels, descending beyond the six-thou- 

 sand-foot line, while south of this both the increasing 

 moisture of the winds and the decreasing average tem- 

 perature favour the increase of ice-fields and glaciers. Con- 

 sequently, as Darwin long ago observed, the line of per- 

 petual snow here descends to an increasingly lower level, 

 and glaciers extend down farther and farther towards the 

 sea, until, in Tierra del Fuego, at about latitude 45°, they 

 begin to discharge their frozen contents directly into the 

 tidal inlets. Darwin's party surveyed a glacier entering 

 the Gulf of Penas in latitude 46° 50', which was fifteen 

 miles long, and, in one part, seven broad. At Eyre's 

 Sound, also, in about latitude 48°, they found immense 

 glaciers coming clown to the sea and discharging icebergs 

 of great size, one of which, as they encountered it floating- 

 outwards, was estimated to be " at least one hundred and 

 sixty-eight feet in total height." 



In Tierra del Fuego, where the mountains are only 

 from three thousand to four thousand feet in height and 

 in latitude less than 55°, Darwin reports that "every val- 



