124 LYELL'S ELEMENTS OF GEOLOGY. 



Rocks altered by Granite Veins, 



Fig. 111. 







^^^^^^^^^^^^^^ 



Junction of granite and argillaceous schist in Qlen 

 Tilt. (MacUulloch.)* 



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- 



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 horn stone or chert, with a splintery frac- 

 ture, effervescing feebly with acids. 



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



