460 Cleavage and Foliation. paet ii. 



E. is the cominonest direction ; this likewise holds good 

 with the cleavage of the altered feldspathic clay-slates, 

 occasionally met with on the coast for ninety miles north 

 of Valparaiso. Some feldspathic slate, alternating with 

 strata of clay-stone porphyry in the Bell of Quillota 

 and at Jajuel, and therefore, perhaps, belonging to a 

 later period than the metamorphic schists on the coast, 

 cleaved in this same direction. In the eastern Cordillera, 

 in the Portillo Pass, there is a grand mass of mica- 

 slate, foliated in a north and south line, and with a 

 high westerly dip : in the Uspallata range, clay-slate 

 and grauwacke have a highly inclined, nearly north and 

 south cleavage, though in some parts the strike is irreg- 

 ular : in the main or Cumbre range, the direction of the 

 cleavage in the feldspathic clay-slate is NW. and SE. 



Between Coquimbo and Guasco there are two con- 

 siderable formations of mica- slate, in one of which the 

 rock passed sometimes into common clay-slate and some- 

 times into a glossy black variety, very like that in the 

 Chonos Archipelago. The folia and cleavage of these 

 rocks ranged between [N" . and N TV. by N.] and [S. and 

 STV. by S.] Near the Port of Guasco several varieties 

 of altered clay-slate have a quite irregular cleavage. 

 Between Guasco and Copiapo, there are some siliceous 

 and talcaceous slates cleaving in a north and south line, 

 with an easterly dip of between 60° and 70° : high up, 

 also, the main valley of Copiapo, there is mica-slate 

 with a high easterly dip. In the whole space between 

 Valparaiso and Copiapo an easterly dip is much more 

 common than an opposite or westerly one. 



Concluding Remarks on Cleavage and Foliation. 



In this southern part of the Southern Hemisphere, 

 we have seen that the cleavage-laminas range over wide 



