565 



many has been supposed to extend to Potosi, that is 

 840 geographical miles. The grand vein is always 

 nine feet in thickness ; but on both sides numerous 

 veins branch off, which may be said to penetrate 

 in all directions a chain of mountains 30 miles in 

 breadth*. From this surprising example,. an idea 

 may be formed of the extent of some veins, which 

 have continued to be richly productive after the 

 labours of many centuries. 



In conducting their subterranean operations, Mines, 

 the miners use a kind of compass, divided into 

 twice twelve hours; 12 and 12 being N. and s, 

 while 6 and 6 are E. and w.f This is used to 

 estimate the direction of the vein; while its incli- 

 nation is measured by the plummet The dip is 

 often confounded with the inclination, but seems 

 more properly to imply the general declination, 

 taken in the line or direction of the vein, than -.the 

 lateral inclination or obliquity. Thus if a book 

 be held obliquely, the back will show the direc- 

 tion of the vein, which is seldom strictly horizontal, 

 but dips at one extremity, while at the other it is 

 salient ; or, in the language of miners, bassets out, 

 or rises to the day. The width of the back shows 



* Molina, 1st. Nat. del Chili. 



f Invented by the Germans, the fathers of modern mineralogy. 

 The silver mines in the Hartz were discovered A, D. 968. Those 

 :>f Saxony, by a Hartz miner, about A. D. 1180. 



