PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 515 
Some fifty yards to the east, it is almost as nearly white. Here the labra- 
dorite greatly predominates. The whole character of the rock has at the same 
time altered. 
The labradorite is now the matrix, the hornblende the porphyritically dis- 
posed substance. 
The labradorite, instead of occurring in large striated translucent crystals, 
is now granular to structureless. The hornblende occurs to about the seventh 
part only of the bulk of the labradorite ; it is now light green and somewhat 
platey,—it may be wralite. The appearance is similar to what a quantity of 
chopped leeks diffused through cold suet would present. 
This, though so contiguous in position to the first described, is the furthest 
removed in mineral constitution in one direction—that, namely, in which the 
felspar is in excess. The change, however, is elsewhere much more marked in 
other respects. — 
Immediately to the east of the harbour of Portsoy, the structure of the rock 
is distinctly laminated, when considered in hand specimens; and clearly 
bedded,—the beds frequently exhibiting well-marked contortions. The felspar 
and hornblende are here separated into belts; the structure altogether is 
gneissose. 
A third set of beds, which, though not altogether the same in composition 
(for they contain small crystals of Paulite and are cryptocrystalline), must 
be assigned to the same general type, occurs higher up in the series, on 
the west shore of the bay of the Durn. Within a space of some sixty yards, 
this rock alternates—at least five times,—with an equal number of beds of 
serpentine. The augitic type of mineral, also, here prevails, if it does not 
absolutely exclude the hornblendic ; Paulite and Biotite in small quantity find 
a place ; the felspar is the same. 
The variety first described was stated to present occasionally a flake of 
brown mica (Biotite 2). This mica in the upper beds takes the place—in in- 
creasing quantity as we pass eastward—of the augite, and of what hornblende 
may be present ; and it is this increased and ultimately total replacement of 
the one for the other, which forms a rock which can be referred to diorite with 
so much difficulty. Varieties which show the augite and Biotite in nearly 


equal amount are to be seen, in large pattern, in the heights above Cowhythe 
Head ; while the rock which forms the cap of—or at least occurs immediately 
eastward of the granite of—Barry Quarry, has a minute, almost granular 
structure, with apparently no hornblende. 
The total replacement of augite by Biotite gives rise to the variety which 
| departs to the most marked extent from the typical. This is to be seen in 
_beds on the shore near to East Head and a little to the west of Cowhythe 
| Head, where the rock consists solely of white labradorite and bronzy Biotite ; 
