52 



ture is, that dipping southward at a flat angle under a heavy hill. 

 In a series of parallel fractures the bunches of mineral will be 

 found in a more or less meridional direction (Plates VII. and 

 VIII.), on the south somewhat deep, and on the north shallow 

 deposits. This rise of the metalliferous currents varies in South 

 America from 10° to 20° from the horizon. In Mexico the 

 richer bunches of minerals are found in the parts where the 

 fissures intersect the moist porphyritic varieties of clay-slates. 

 (Plate VII.) In New Grenada, Peru, Chili and the Brazils, 

 similar channels of rocks are equally productive. In a word, 

 every mining district have their conducting metalliferous chan- 

 nels, and the whole accumulated evidence obtained in all parts 

 of the world clearly proves the fact, that the contents of the veins 

 of fractures depend on the character of the rocks they traverse, 

 as represented in the sketches. 



It is of great importance to bear this fact in mind, because 

 veins which have been particularly rich at one place have led 

 persons to suppose that the continuation of the same fracture 

 must lead to more riches, although such a fracture may intersect 

 barren rocks. Every mining establishment ought to be in pos- 

 session of the general bearing and undulations of their respective 

 metalliferous channels, without which the work must be attended 

 with great risks : guess work, " where it is there it is" is an ex- 

 tremely bad principle to go by, even with a good practical miner ; 

 but when exposed to the changes of agents, inexperience, &c, 

 the consequence may be easily conceived. After great expense 

 has been incurred in carrying on works through unproductive 

 rocks, mines have frequently been abandoned, when within a few 

 feet of rewarding ouk search, for the want of knowing the width 

 and positions of the barren and rich channels of ground. On 

 the other hand, in prosecuting works of discovery in a direction 

 where no metalliferous channels exist, mines have been carried 

 on at a considerable loss, simply because the vein happens to 

 be in the same direction as another more productive. Of all 

 speculative employments, mining has been, and continues to be, 

 for the want of a well-founded principle, the most uncertain ; ex- 

 perience and ingenuity being frequently and completely defeated, 

 although the miner has been continually led to suppose himself 

 on the point of meeting a good course of ore ; while from veins, 



