6 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
the veins are cut by others. In one of the smaller openings of the granite 
quarry of Anguston this is admirably seen: here a darker shaded, finer grained, 
and narrower set of veins cuts others, which are wide, and which are paler in 
colour than the ordinary granular rock. 
The numberless quarries which pockmark Aberdeenshire afford unusual 
facilities for studying its “ grey granite ;” such study, whenever entered upon, 
tends to the conclusion that the granite results from the metamorphism of the 
gneiss in which it is everywhere embosomed, and with which it is so intricately 
wrapped up. 
In this district the metamorphism appears to have taken place under three 
different sets of circumstances. 
In the first of these,—by what may be called a gradual incrementation of 
the granitic over the normal gneissic structure. 
In the second,—by an abrupt and, as read by the eye alone, an inexplicably 
sudden transition of the latter into the former. 
In the third,—by a general fading or softening away of the transmutible into 
the transmuted. 
Throughout the whole of the gneiss of central Scotland, and more especially 
in these districts where the rock exhibits the clearest marks of alteration, it is 
pervaded by granitic bands, which, there is reason to believe, have not un- 
frequently been considered to be intrusive or injected veins. 
That they are not so, but are merely the segregation of certain of the 
mineral constituents of the rock—like consorting with like—is evidenced by the 
following four facts. 
These bands or layers of felspathic and quartzy matter invariably follow 
implicitly every flexure of the rock (developed and disclosed by the adjacent 
micaceous layers), never cutting across these or branching to the smallest 
extent. They do not maintain anything of a uniform width, but repeatedly 
diminish and expand, in accordance with the abruptness or looseness of the 
folds into which the rock is thrown. Though highly felspathic, and often 
markedly crystalline, they exhibit unmistakably in some portion of their bulk 
a laminated arrangement of particles, which becomes more and more distinctly 
pronounced as it passes into the ordinary structure of the rock. The blow of 
a hammer recognises no point at which the two structures are of facile separa- 
tion; the transition of the one into the other being so gradual that no two 
persons would agree as to the point where each terminates,—and a hand- 
breadth would not cover the debatable space. 
The ingredient of mica, moreover, is markedly deficient in these so-called 
granitic bands. 
I instance the north-east side of the hill of Scoltie, near Banchory, as a 
locality where such “veins ” may be studied, specially in connection with the first 
of these changes ; because about a couple of miles north of this, in the railway 
