VEINS THEIE NATUKE AND OKIGIK 



VEINS AND DYKES, HOW OCCASIONED METALLIFEROUS VEINS, MOST 

 ABUNDANT IN THE PRIMARY ROCKS REASON OF THIS ABUND- 

 ANCE GENERAL CHARACTERISTICS OF VEINS VARYING NATURE 

 OF THE MINERAL SUBSTANCES BY WHICH VEINS ARE MAINLY 

 FILLED MODE IN WHICH THESE VEIN-STUFFS ARE AGGREGATED 

 RELATIONS OF THE ORES TO THE VEIN-STUFFS DIRECTION OF 

 VEINS IN CERTAIN LOCALITIES RIGHT-RUNNING AND CROSS VEINS 

 THEORIES OF FORMATION AND FILLING INFILTRATION AND 

 DEPOSITION OF CHEMICAL SOLUTIONS EFFECTS OF THERMAL 

 AGENCY ELECTRIC AND OTHER KINDRED CURRENTS RELATIONS 

 TO CENTRES OF IGNEOUS ACTION IMPORTANCE OF METALLIFER- 

 OUS VEINS CONTRAST BETWEEN THE MINERAL AND AGRICUL- 

 TURAL VALUE OF PRIMARY DISTRICTS MINES AND STREAM- 

 WORKS MINING INDUSTRY, AND IMPORTANCE OF SOUND GEO- 

 LOGICAL DEDUCTION. 



IT has been stated in the preceding Sketch, that of all the 

 rocks in the earth's crust, the primary are those most abun- 

 dantly traversed by veins. As these veins are the great 

 repositories of the metallic ores, it may be useful at this 

 stage briefly to explain what veins are, how they occur, and 

 what the general character of their contents. This informa- 

 tion may lead to a better comprehension of much that will 

 be subsequently stated, at the same time that it is valuable 

 knowledge of itself, and belongs to one of the most inter- 

 esting departments of modern geology. 



It was mentioned under Vulcanicity, that in all volcanic 

 areas the solid crust was more or less rent and fissured 

 these rents either radiating from some centre of eruption, 



