EXPLANATION OF SECTIONS. 275 



the mouth of South Evans gulch, and in Section L joins the slight fold at 

 the south face of Prospect Mountain. The form of the east-and-west folds, as 

 shown in Sections L, M, and N, along the base of Prospect Mountain, sug- 

 gests that the mass of Prospect Mountain afforded more resistance to com- 

 pression than the adjoining country to the south, so that the folds are com- 

 pressed sharply up against it. The reason of this may be found perhaps in 

 the unusual thickness of the porphyry bodies on Prospect Mountain, which 

 are probably much less plastic than the sedimentary beds. 



