DEBRT8 OF GLACIERS. 90 



4, Transport and Deposit of Rocks by Floating Ice. 



When fragments of rock are transported by the 

 water, it carries the smaller and lighter sand to a 

 greater distance than the heavier, this again to a 

 greater distance than stones or pebbles, and these 

 latter, of course, much farther than great blocks of 

 stone. These materials of the earth's crust find also 

 a powerful and majestic means of transport in floating 

 ice; but it carries its load without discrimination, 

 and deposits fragments of all sizes aud of every de- 

 scription that may chance to be imbedded in its 

 mass. During winter we see our rivers covered with 

 a sheet of ice : the spring returns, the frozen surface 

 is melted, and masses of ice float seaward in dis- 

 ordered heaps. This phenomenon constitutes an 

 annual break-up. Where the water touches the shore 

 stones and earth become imbedded in its solidified 

 mass. If the river be completely frozen in its whole 

 depth (which happens sometimes in northern coun- 

 tries), its bed as well as its shores will load the ice with 

 debris, which is thus transported to a distance. 



This phenomenon, which we witness once a year, is 

 produced on a grand scale in the polar seas. On 

 those inhospitable shores the rivers of ice, called 

 glaciers, glide down from mountain heights into the 

 .sea, and carry on their surface, as well as m their 



