124 



LYELL'S ELEMENTS OF GEOLOGY. 



Rocks altered by Granite Veins. 



Fig. 111. 



Junction of granite and argillaceous schist in Glen 

 Tilt. (MacCulloch.)* 



intruding itself in tortuous veins into the beds of clay-slate and 

 limestone, from which it differs so remarkably in composition. 

 The limestone is sometimes changed in character by the prox- 



Fig. 113. 



Junction of granite and limestone in Glen Tilt. 

 a. Granite. b. Limestone. 



c. Blue argillaceous schist. 



imity of the granitic mass or its veins, and acquires a more com- 

 pact texture, like that of hornstone or chert, with a splintery frac- 

 ture, effervescing feebly with acids. 



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



