172 Proceedings of the Royal Fhysical Society. 
degree of metamorphism and the absorption of felspar, when 
in a soft state through heat, into gneiss ; and, finally, by 
absolute fusion with the felspar, into granite. All these 
gradations are seen here in the most instructive manner, and 
in every variety. 
The Peterhead granites are chiefly composed of red felspar 
and quartz, the mica being very subordinate. They are 
occasionally fine-grained and light grey, like the Aberdeen 
granite, and enclose numerous fragments of schists. At one 
place, upon the shore, near Peterhead, a dyke of very beau- 
tiful flesh-coloured felspar, about twenty-four yards wide, 
runs E. by S. to W. by N. This is occasionally granitoidal. 
Near this is a large mass of felspar or felspar porphyry, con- 
taining veins and nests of quartz. Along this part of the 
shore the felspar rock is more abundant than the granite. 
It is also met with in the Stirlinghill quarries. The Aber- 
deenshire granites appear to be simply the result of the in- 
vasion, upon a large scale, of the primary schists and quartz 
rock, by this standard igneous rock. The nature of the re- 
sulting granite depends wholly upon that of the associated 
schists. 
To the foregoing examples many others might be added, 
but those given have been selected on account of the clear 
and instructive character of the junctions, and their compara- 
tively ready accessibility. Fassney Water and Glen Tilt, 
both classic in geology, might have been added ; but as this 
paper has already exceeded the limits intended, it would 
be improper at present to enter at greater length upon 
the subject, although it is one admittedly of very high 
interest. The writer trusts that his labours in this field 
may induce other and more competent observers to examine 
and thoroughly test the correctness of his investigations, 
by a direct appeal to the rocks themselves. He would par- 
ticularly impress upon observers the importance of taking 
notes of the positions of the divisional planes of the granites 
and porphyries, and comparing them with the directions of 
the planes of stratification of the nearest rocks of aqueous 
origin. 
