285 
1911-12.] Report on Rock Specimens. 
micaceous shale or flag and a small piece of red grit, which could be 
matched with rocks from any of the great subdivisions of the Old Red 
Sandstone from the north of Scotland. Outliers of the Old Red Sandstone 
which could supply such fragments occur as far west along the north 
coast of Sutherland as Tongue and Eilean nan Ron, and may extend under 
the sea much further to the northwards. 
A considerable number of small specimens are undoubtedly of 
Secondary age. Of these, two angular fragments of a dark calcareous 
sandstone with grains of magnetite, one with the cast of a belemnite, 
a piece of dark oolitic limestone, and a fragment of calcareous sand- 
stone like some of the Brora rocks, appear to belong to members of the 
Jurassic series. 
Two small specimens of ochreous weathered limestone, full of casts of 
foraminifera, probably represent some Cretaceous limestone. 
The remaining sedimentary pebbles are of uncertain age. One is of a 
well-rounded hard green grit, probably a pebble out of a Torridonian or 
Old Red Sandstone conglomerate, the other a small, well-glaciated fragment 
of hard greenish grit or conglomerate with quartz veins (probably Torri- 
donian), and a rounded pebble of dark crystalline limestone, which may be 
a metamorphic marble. 
The metamorphic rocks are represented by twelve fragments of granulitic 
gneiss or schist of Moine type, the two largest of which are angular and the 
rest well glaciated. Some of them are quartz granulites with white mica, 
in a comparatively low stage of metamorphism, in which some of the 
original grains of quartz are only peripherally granulitised, indicating that 
they come from near the western limit of these schists and close to the 
Moine thrust-plane which traverses North Sutherland in a north-north- 
east direction and passes out to sea a little to the east of Loch Erriboll 
Others, completely granulitised and with biotite, are in a higher stage of 
metamorphism, like the rocks further to the east. Among the meta- 
morphic rocks is a small glaciated fragment of augen-gneiss, a foliated 
igneous rock with eyes of felspar. It resembles a foliated “ Cansip 
Porphyry,” and probably comes from the zone of “ mylonised ” rocks in 
immediate proximity to the Moine thrust-plane. 
The igneous rocks are represented by nine specimens, all of which are 
glaciated. Of these, one is of diorite, one of quartz felsite with porphyritic 
felspar and quartz blebs, set in a fine-grained green ground-mass. The 
remaining seven specimens are of dolerite. Such dolerites are widely 
distributed in central Scotland, but are rare in Sutherland, Caithness, 
Orkney, and Shetland. 
