consequence of the polar action, viz. meridional grain or laminae, 

 splits, and transverse or east and west fractures. Besides these, 

 numerous smaller fractures must occur according to circum- 

 stances ; but as they are of minor importance and of a local 

 character, we need not take them into consideration. 



We have already shown that the polar grain is universally 

 observed ; the east and west fractures intersecting this structure 

 are seen in the Brazils and Chili, forming immense veins of 

 quartz. In Peru and Quito they are veiy abundant. In New 

 Granada, on the western Cordillera, which is principally formed 

 of porphyritic granite, the east and west fractures are very 

 numerous, and are generally filled with quartz and auriferous 

 pyrites, being the principal metalliferous solvents of this chain. 



The central Cordillera is very schistose, thus possessing great 

 tenacity and capable of being elongated ; consequently the trans- 

 verse fractures are but few, and confined to subordinate gra- 

 nular channels : the longitudinal and diagonal splits are of or- 

 dinary occurrence, the sides are commonly grooved and highly 

 polished by friction caused by the meridional movements of the 

 parallel masses. The hornblendic, calcareous and talco-mag- 

 nesian varieties are found extremely active in the above series. 

 The eastern Cordillera is very quartzose, therefore the east and 

 west fractures are very numerous, and are intersected by a few 

 polar splits, with striated and polished sides. In Mexico the 

 porphyritic variety predominates, and the meridional splits are 

 consequently intersected by a great number of fractures. (See 

 Plate VII.) In Cuba and the other large islands of the West 

 Indies the same phenomena are observed. In the southern de- 

 partments of the United States, and especially at Virginia, the 

 polar splits predominate. These splits have cleaved the coal 

 beds of Blackheath into longitudinal fragments, causing great 

 disorder in their position. (See Plate XVI.) In Cornwall they 

 are very numerous ; the splits are known by the names oi fluccan 

 and cross courses (Plate VIII.), and the transverse fractures are 

 called lodes. It is in the fractures that the mineral wealth of 

 this county is found. 



The great polar splits of Cornwall and Devon extend across 

 the Bristol Channel to Wales, and have cut the coal fields and 

 all the sedimentary rocks of the province into meridional strips. 



