OLD RED SANDSTONE OF WESTERN EUROPE. 371 
Sarclet a protraction of the angles of dip gives a total thickness of strata 
amounting to about 9000 feet ; so that either the series is rather thicker on the 
north side of the trough, or the effect of some small faults is to repeat portions 
of the strata so as to cause them to be reckoned twice in the estimate. At 
Sarclet the rocks arch over, and then dip to the north-west. The lower or red 
sandy portion of the Caithness development of the Old Red Sandstone is then 
repeated on the northern side of the anticlinai axis to beyond Ires Goe, fully 
2500 feet of strata being exposed along the cliffs before the more flaggy series 
begins. To the east of Hempriggs House, however, another dislocation occurs, 
whereby a portion of the lower red beds is once more carried up to the surface. 
The dip thereafter remains more steadily towards north-west, bending towards 
north-east at Staxigoe, flattening and undulating towards Noss Head, and then 
turning round at Castle Sinclair towards noith-west as far as Ackergill, where 
the centre of another synclinal trough is reached. It is hardly possible at 
present to say definitely, or within other than tolerably wide limits, what may 
be the cumulative effects of the obviously small faults which occur in the strip 
of coast-line between Sarclet and Ackergill. Probably somewhere about 3500 
feet of flagstones are exposed between the Old Man of Wick and Ackergill. 
This, added to the 2500 feet of red strata extending southwards to the Sarclet 
axis, would give a total depth of 6000 feet. The coast-line northwards from 
Ackergill runs very nearly along the line of strike on the west side of the 
Sinclair’s Bay syncline. After passing Brough Head we begin to descend 
slowly in the flagstone series ; but before any considerable thickness of strata 
is passed over we encounter a set of yellow and red false-bedded sand- 
stones, which perhaps lie unconformably on the flagstones, and occupy the 
north-western side of Freswick Bay. At Skirsa Head the flagstones reappear, 
aud continue to dip at low angles in a general southerly direction as far as 
Fast Goe, where they are faulted against another mass of red and yellow sand- 
stone, beyond which they reappear on the further side of a second fault, and 
form the bold bluff promontory of Duncansbay Head. It is evident, therefore, 
that along the eastern coast the first portion of the section, or that which runs 
from the granite of Ousedale to the centre of the synclinal fold at Latheron, 
affords the best evidence of the succession of the strata, and can best be com- 
pared with, and supplemented from, the other exposures of the same beds, as 
they are repeated by successive anticlinal and synclinal folds. 
Comparing the rocks in that part of the section with those exposed along 
the northern coast-line, we soon perceive that the latter, on the whole, differ 
considerably in lithological character from those on the east coast. Taking 
this fact in connection with the general seaward inclination of the beds in the 
interior, from the Sutherlandshire moors northwards to Holburn Head, we cannot ° 
hesitate to place the northern series on a higher general horizon than the 
