Ch. VIII.] THE GRANITIC AND SCHISTOSE ROCKS. 159 



manner. Crystals of this hornblende may be observed 

 shooting far into the body of the schist, so as to render it 

 often difficult to assign the limits of each rock : and, in a less 

 degree, the quartz and felspar exhibit the same appearance. 

 Together with this, the schist is singularly contorted, being 

 bent, broken, and intermingled in a most confused manner 

 with the rock that traverses it, while distinct detached frag- 

 ments are often involved in the mass of the granite : in many 

 instances, these fragments either exhibit at their edges a 

 change into a substance resembling basalt, or are actually 

 converted into a black matter, which has, at first sight, the 

 aspect of a fine-grained hornblende-rock, or a basalt of the 

 blackest hue, and which only an accurate inspection discovers 

 to be modified fragments of schist. 



The district of Rannoch, observes the same author*, offers 

 a multiplicity of granite-veins, which are so confounded with 

 each other, and with the rocks which they traverse, that their 

 appearance cannot be accurately described. They frequently 

 vanish so imperceptibly, both in the quartz-rock and the 

 mica-slate, that a perfect passage from the one to the other 

 is visible, while the accession of additional veins, traversing 

 and often shifting the already intricate structure, increases 

 the unexampled confusion which reigns among them. The 

 granite is often imbedded in detached lumps in the schist ; 

 and it is worthy of remark, that, however minute they may 

 be, contrary to the granite-veins of Glen Tilt and Corpach, 

 their character is perfect even to their minutest division. 



The granite-veins at Glen Tilt are found traversing strata 

 of limestone-schist and quartz-rock; and possess a farther 

 interest, independent of their geological relations, as having 

 afforded Dr. Hutton one of the original arguments on which 

 his theory is founded. Having already described all these 

 rocks^ and the nature of their connection, the granite- veins 

 by which they are intersected may be more easily under- 

 stood. 



* Geol. Trans,, vol. iv. p. 130. 



