11 



Four chief varieties of veins have been named depending- 

 on these conditions : 



1. Rake or fissure veins. These are perpendicular, or 

 nearly so, in direction, and vary little in width as they de- 

 scend. 



2. Pipe veins are much like fissure veins in direction, 

 being often nearly perpendicular, but they are irregular in 

 width, and are subject to great variations, being now very 

 wide and then very narrow in diameter. 



3. Flat veins or streaks. These are a variety of fissure 

 veins which change their direction and run along parallel to 

 the beds. 



4. Gash veins are those which resemble fissure veins, 

 but are wide at the top and gradually narrow to a point until 

 they disappear. 



The vein is from its nature shut in by walls. These 

 walls, if cracked when the vein matter or gangue was deposit- 

 ed, were often penetrated by portions of the liquid intrusive 

 matter, and so the wall rock contains at times, many feet from 

 the vein, traces of the vein material. When strings of the 

 vein material thus penetrate the wall rock, the rock is spoken 

 of as " ridered," though miners wrongly call these strings 

 '•' feeders." Sometimes the same mineral as that of the vein 

 may be found in pockets or nests adjoining the vein. 



In some veins the richer part of the vein is in the centre, 

 and there seems a regular arrangement of the different miner- 

 als according to the specific gravities of the minerals. 



When veins cross one another it is found that the place 

 of junction is very rich in mineral deposit. This is really not 

 accounted for, but is said by some to depend on thermal or 

 even on electric conditions. Contents of veins are often found 

 to vary with their depth. The length of a vein is hardly 

 ever known. The richest veins are productive for a while, 

 but their fissures may be filled with other materials than 

 those desired, or may cease altogether. Some, however, are 

 known to extend for several miles. Veins vary greatly in 



