OPERATIONS OF WATER. 



21 



ACTION OF WAVES UPON A 11OCKY SHORE. 



hills ; and in the northern regions it forms great 

 glaciers, or masses of solidified snow, many miles 

 in extent, and many hundred feet thick. These 

 glaciers descend by slow, imperceptible degrees, to the 

 sea ; their edges break off and fall into it, and, 

 floating southward, sometimes in great mountainous 

 masses, are seen by man in the shape of .icebergs. 

 Frequently huge rocks, that have fallen upon these 

 glaciers from cliffs in the arctic regions, are carried 



