SUPPLEMENT. 



the Council of Mines in Saxony, has informed us 

 that the mere fissures of rocks are commonly very 

 narrow ; while a vein, on the contrary, may be of 

 prodigious extent, and is always filled with a sub- 

 stance different from that of the mountain. He 

 wa& the first, according to Werner, who establish- 

 ed the essential difference between veins and 

 fleet ze, or beds, which may be metallic and con- 

 tain a heterogenous substance, yet must not be 

 called veins, as they follow the direction of the 

 other strata. 



Arrects. Many primitive mountains consist of what have 

 been called, with great impropriety, vertical strata 

 or beds ; while the latter words of themselves im- 

 ply a horizontal position. The terms arrects or 

 uprights have been here proposed and adopted, 

 in order to obviate a -solecism long regretted by 

 writers on mineralogy. Such mountains consist- 

 ing of arrects, are often intersected by veins, which 

 cut these arrects in an opposite direction. 



Origin. It seems a probable opinion that many veins of 

 great extent may have been produced by the de- 

 siccation of the globe, after the retreat of the 

 primeval waters; while others may be owing to' 

 the subsidence of parts of mountains resting on/ 



Extent, an irregular nucleus. At Uspallata, in the Andes 

 of Chili, there is a vein of silver, which has been 

 traced to the enormous length of 90 miles \ but by 



