2()2 N. S. SlIALER — FORMATION OF DIKES AND VEINS 



veins are prepared for by the formation of somewhat gaping fissures, and 

 that these rents, after being more or less completely closed, are reopened 

 by faulting on the plane of the deposit, such original or secondary spaces 

 are not required for the development of a vein. The other point is that 

 the pressure of the growing vein, which in the case of the geode is able 

 so to condense the rock matter about it as to win room for the dejiosit, 

 is likely to be even more effective in the group of tabulate deposits in 

 forcing the walls asunder. 



Condensing and Dkforming Effects of Vein and Dike Materials 



In this connection it may be well to note that the introduction of large 

 amounts of vein and dike material brought from lower to higher levels 

 of the rocks is likely to prove an important source of condensation and 

 deformation of the beds in which the deposits are formed. I have else- 

 where referred in some detail to the importance of this action. It clearl}'- 

 deserves more attention than it has yet received. 



