GEOLOGICAL SOCIETY OF PENNSYLVANIA. 377 



CHAPTER II. 



The appearance of a fissure or rent in the rocky crust 

 of the earth, approaching more or less to a vertical di- 

 rection, and filled with metallic ores, will perhaps con- 

 vey the clearest idea of the nature of a metalliferous vein; 

 the object of mining being to break down and transport 

 to the surface the contents of this supposed rent, or, in 

 other words, to cut out from between the environing 

 rocks this thin metallic plane. To eifect this, galleries, 

 called " levels,''^ are driven horizontally on the vein, one 

 above the other, and the ores, &c. produced by their 

 excavation, are transported to the surface by large buck- 

 ets called '^kibbles,'^^ which are let down and raised up by 

 machinery, through perpendicular pits or '^shafts/^ cut- 

 ting the former at right angles. The horizontal galleries 

 are, in the first instance, about 2 feet wide and 6 feet 

 high, but varying of course according to circumstances, 

 and being frequently extended much beyond their origi- 

 nal dimensions. They are driven one above the other, 

 at intervals from 10 to 20 or 30 fathoms. When ex- 

 tended to a certain distance from the original shaft, it is 

 necessary, for the sake of ventilation, as well as for other 

 reasons, to form a second shaft, which traverses all the 

 galleries, in the same manner as the first. The distance 

 between shafts is very various, being from 20 to 100 fa- 

 thoms. Frequently a communication is made between 

 two galleries, by a partial shaft, (called a wins) in the 

 interval between two shafts. When there are more than 

 one lode worked in the same mine, as frequently happens, 

 galleries or levels often run parallel to each other at the 

 same depth. In this case they often communicate by 

 intermediate galleries, driven through the rock, (or 

 couniiy, as miners term it) which are called cross- 

 cuts.^^ A mine thus consists of a series of horizontal 

 galleries, generally one above the other, but sometimes 



