370 PROFESSOR GEIKIE ON THE 
west, are overlaid by the thick but lenticular band of white quartz-rock of the 
Scarabin Hills. Higher still in the series, but forming a band of lower ground 
on the north side of these hills, comes a remarkably beautiful gneiss, in which 
the most distinguishing feature is the occurrence of abundant wavy ribbons and 
irregular kernels of pink orthoclase. Other bands of white quartz-rock and 
dark schist occur further to the north. Veins of pink granite and pink quartz- 
porphyry or elvanite abundantly traverse all the crystalline rocks. In tracing, 
therefore, the limits of the conglomerates and breccias at the base of the Old 
Red Sandstone, we find them to indicate with considerable distinctness the 
character of the more ancient rock beneath them. Near the granite they are 
made up in great measure of granitic debris. Round the quartz-rock they are 
largely composed of that material. The existence of the well-veined orthoclase 
gneiss is indicated some distance before the underlying rock is actually seen by 
the abundant fragments of beautifully fresh cleavable pink felspar in the con- 
glomerates. Hence, even when faults occur between the conglomerates and 
the rocks of the older platform, they do not materially obscure the section, as 
the connection of the fragmental with the contiguous crystalline masses remains 
sufficiently clear. As on the southern margin of the Highlands, so here, the 
crystalline or metamorphic character of the older rocks was as distinct as now 
before the formation of the conglomerates. The metamorphism of the gneiss 
quartz-rock and other associated bands, and the extravasation of the multitude 
of granite and quartz-porphyry veins, had been completed long before any 
portion of the Caithness Old Red Sandstone began to be laid down. And, as 
elsewhere throughout the Highlands, the denudation of these metamorphosed 
rocks must already have been enormous before any of the now visible con- 
glomerates were formed. 
The eastern coast-line of Caithness shows at its southern extremity a portion 
of the granite of the crystalline platform, forming the high headland of the 
Ord. A small fault intervenes at the Ousedale Burn between the granite 
and the Old Red Sandstone, its effect being to cut out some of the base- 
ment conglomerate. From this point, however, the strata can be followed in 
ascending order as far as Berriedale village, where, a little to the north of the 
mouth of the river, a considerable fault cuts the cliff, and extends inland along 
the southern flank of the Scarabin Hills. By means of this dislocation, and a_ 
reversal of the dip, a low portion of the series is again brought up, including 
part of one of the conglomerate masses. A steady dip towards north-east and 
east now sets in as far as Latheron, so that, from the axis of the conglomerate 
near Berriedale to that place, there must be included a thickness of at least 
8000 feet of strata. Beyond Latheron the beds rise again with a south-westerly 
and then a westerly dip as far as Sarclet, where the Berriedale conglomerate 
once more rises to the surface. From the centre of the trough at Latheron to 

