HEAT 



VEINS. 



329 



292. 



.^y^f^^i^f;>^:^M}ify},i _ 



followed under the pressure in action, if the rock had had no grain. Or there 

 may have been many spaces opened by tension between the bedding with- 

 out connections across. Again, the spaces may be simply the thin open- 

 ings between the laminae or leaves of a fine-grained schist or slate, of 

 almost paper-like thinness (Fig. 290), like the spaces between the leaves in 

 a folded quire of paper, so that the veins (which are usually of quartz) look 

 like delicate interlaminations of the slate. 

 Moreover, under an oblique warping of the 

 beds by the fissure-making pressure, vari- 

 ous irregularities are made in the opened 

 spaces. 



The process fills the opened spaces, and 

 makes the shattered rock again solid, even 

 when it is broken to fragments that lie 

 touching at angles instead of being simply 

 fissured. An example (from Cornwall, 

 Eng.) is shown in Fig. 292, in which gran- 

 ite extends in veins into slate. Such cases 

 are common ; and not unfrequently, in the 



same region slate or schist occurs in masses inside the granite, as in Fig. 495, 

 page 448. The following figures represent three parts of one large gran- 

 ite vein, from gneiss, on the coast south of Valparaiso, where veins are 



Granite veins in slate. De la Beche. 



293. 



294. 



i.^.Jli.jl 



295. 





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Granite veins, Valparaiso. D., '49. 



very numerous and of all sizes. The figures show quite accurately the 

 bedding of the micaceous gneiss along the sides of different parts of the 



