CHAPTEE IV. 



THE DENUDANTS, OR CARVERS OF THE EARTH' S 

 SURFACE SEA ACTION. 



THERE are various agents to whose operations, com- 

 bined with the effects of contraction or shrinkage 

 (joints, cracks, faults, and the like), must be attributed 

 the diversified conformations of the earth's surface. 

 These carvers of the earth are the sea, ice, the sun, 

 cold, heat, wind, rain, rivers, and chemical action. 

 Cold in this classification includes ordinary frost; 

 while ice refers only to the work done by glaciers 

 and icebergs. Heat and the sun also form distinct 

 headings. These two agents are kept separate, 

 .because their modes of action are entirely different ; 

 for although the latter is a source of heat capable 

 of forming surface cracks and other fissures, 

 yet many of the deep-seated joints must be due to 

 the effects of the internal heat of the earth. None 

 of these workers appear capable of doing much work 

 when unaided. The sea cannot act effectively with- 

 out the sun, chemical action, and wind, to open the 

 cracks, joints, and the like, and to raise the storm and 



