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Veins are sometimes, like strata, fractured, and 

 the fractured parts either remain in contact, or 

 are separated (shifted) so as no longer to be in the 

 same plane. Such fractures are sometimes occu- 

 pied by other veins ; or one vein is intersected by 

 another of the same, or of a different substance. 



In some cases, veins are simple. In others, 

 they divide into two or more, or they give off 

 smaller branches, or, lastly, ramify into successive 

 subdivisions. Such ramifying veins are almost 

 necessarily filaments, at least in their ultimate 

 branches. In such cases, which occur principally 

 in granite, the character of the rock often varies 

 in the progress of subdivision. 



The size of veins is extremely various. 

 Those of granite sometimes descend to that of a 

 thread ; those of the trap family reach to a breadth 

 of an hundred yards and upwards. To the extent 

 of laminar veins, according to the direction of their 

 planes, there are no limits to be assigned. 



The breadth of laminar veins is sometimes the 

 same for a considerable space, or the sides are pa- 

 rallel : in other cases, they are inclined, so that 

 the vein becomes gradually extenuated till it dig- 



