356 



JUNCTION OF GRANITE AND LIMESTONE. [Ch. XXV. 



analogous to those which the contact of a fused mass might be 

 supposed to produce. 



No. 88. 



Junction of granite and limestone in Glen Tilt. 



a, Granite. 



^ Limestone. 



c, Blue argillaceous schist. 



The above diagram from a sketch of Dr. Macculloch, re- 

 presents the junction of the granite of Glen Tilt in Perth- 

 shire, with a mass of stratified limestone and schist. The 

 granite, in this locality , often sends forth so many veins as 

 to reticulate the limestone and schist, the veins diminishing 

 towards their termination to the thickness of a leaf of paper or 

 a thread. In some places fragments of granite appear entan- 

 gled as it were in the limestone, and are not visibly connected 

 with any larger mass, while sometimes, on the other hand, a 

 lump of the limestone is found in the midst of the granite. 

 The ordinary colour of the limestone of Glen Tilt is lead blue, 

 and its texture large grained and highly crystalline; but where 

 it approximates to the granite, particularly where it is penetrated 

 by the smaller veins, the crystalline texture disappears, and it 



