710 



KOCKS ALTERED BY GRANITE VEINS. [Ch. XXXTIL 



I have already hinted at the close analogy in the forms of certain 

 granitic and trappean veins ; and it will be found that strata pene- 

 trated by phitomc rocks have suffered changes very similar to those 

 exhibited near the contact of volcanic dikes. Thus, in Glen Tilt, in 

 Scotland, alternating strata of limestone and argillaceous schist come 

 in contact with a mass of granite. The contact does not take place 

 as might have been looked for, if the granite had been formed there 

 before the strata were deposited, in which case the section would have 

 appeared as in fig. 738 ; but the union is as represented in fig. 739, 



Fig. 7as. 



Fig. m 



Junction of granite and argillaceous schist in 

 Glen Tilt. (MacCulloch.)* 



Fig. 740. 



wmimmw'M 



Junction of granite and limestone in Glen Tilt. (MacCulloch.) 

 Granite. &. Limestone. c. Blue argillaceous schist 



* Geol. Trans., First Series, vol. iii. pi. 21. 



