382 PROFESSOR GEIKIE ON THE 
conical outlier of conglomerate and sandstone forming the Maiden Pap, with 
its knob-roughened sides presenting a sharp contrast with the featureless 
surface formed by the softer red strata on which it rests. 
Westward from this district, it is no longer possible to identify subordinate 
groups of beds in the lower sandy and conglomeratic portion of the Old Red 
Sandstone of this part of Scotland. Even in the Morven area, we see the 
gradual blending of some of the zones which are so distinct on the eastern 
shore. Beyond the water-shed of Caithness and Sutherland, two massive out- 
liers of the same character as Morven form the two isolated conical mountains 
of Ben Griam Mohr and Ben Griam Bheag. Rising steeply from the brown 
waste of peat-mosses between the headwaters of the Halladale and Helmsdale 
rivers, these two eminences afford a most impressive lesson as to the denuda- 
tion of this region since Old Red Sandstone times. They form conspicuous 
landmarks from all the low country to the north and north-west. Their strata, 
inclined at low angles, run in terraced bars along the sides of the mountains 
like lines of masonry, while from their base the platform of crystalline rocks 
undulates in all directions. On the east side of Ben Griam Bheag, well ice- 
worn bosses of grey quartz-rock and gneiss, with veinings of granite and pink 
porphyry, ascend for about a third of the height of the mountain (fig. 2). They 
are unconformably overlaid by a very coarse conglomerate not less than 150 
feet thick, capping an eastern spur of the cone. In this rock the stones 
are tolerably well rounded, and sometimes two feet long. They include pieces 
of pink granite,-greywacke, gneiss, and other crystalline rocks. Above this 
mass lie thick beds of pale reddish and reddish-brown gritty and pebbly sand- 
stone, sometimes passing into conglomerate. In general composition, texture, 
and stratification, these rocks are quite like those of Morven. In successive 
ledges and terraces, they may be followed for a thickness of probably about 
1000 feet to the summit of the mountain, which is formed of a hard conglome- 
ratic bed, dipping, like the beds below, towards south-west at a very gentle 
angle. 


Fig. 2.—Section of Ben Griam Bheag. 
When the wild tracts included within the basin of the Naver are examined 
in detail, other outliers of similar sandstones and conglomerates may be found. 
