376 PROFESSOR GEIKIE ON THE 
' The anticlinal fold at Sarclet has been the means of bringing up on the 
coast-line a coarse conglomerate, which greatly resembles the mass as seen on 
the Berriedale Water, with such differences as might have resulted from a some- 
what greater distance from the source of supply of its materials. The base of 
the rock is concealed by the sea, but a thickness of about 250 to 300 feet is 
visible. The matrix, red in colour, and less strongly felspathic than towards 
the south, contains large and usually rather well water-worn fragments of quartz- 
rock, granite, felspar, porphyry, and red sandstone. It may be matter for doubt 
whether this band should be placed on the same parallel with the basement 
conglomerate or with the brecciated beds of Badbea. On the whole, it seems 
rather to belong to the former, while a probable representation of the Badbea 
breccia occurs higher up in the series at Ulbster. The Sarclet conglomerate is 
distinctly bedded, and in its upper part has intercalated seams and bands of 
red sandstone. The whole of the strata there are considerably contorted and 
broken, though the main inclination and the order of succession remain perfectly 
clear. 
From what has been stated above regarding the conglomerates around 
Reay, it is evident that we cannot be certain that the conglomerate here spoken 
of as the basement subdivision really forms the true base of the whole Old Red 
Sandstone series of this region. If, indeed, we may place the Sarclet rock on 
the same horizon with that of the Berriedale Water, the fragments of red sand- 
stone which it contains serve to indicate the existence somewhere in the neigh- 
bourhood of other and older strata, which may have formed an earlier part of 
the system. We may, however, at least affirm that underlying all the visible 
portions of that system in Caithness it is the oldest known member. Whether 
This evidence was more particularly striking in an examination (made in company with my colleague, 
Mr B.N. Pracs) of the summits of the magnificent precipices which on the west side of Hoy rise 
vertically from the Atlantic breakers to 2 height of more than 1300 feet. Back from the broken and 
ruinous summit the ground is covered with a coating of peat, heather, and coarse grass. Over the 
growing vegetation abundant fragments of sandstone are scattered for a distance of many yards from 
the edge of the cliff. The larger pieces are chiefly flat, and may weigh a pound or more. On lifting 
them the vegetation underneath was found to be quite green, indicating that they had been only recently 
deposited. They are evidently torn by the wind, partly from the crumbling sandstone strata of the cliff, 
partly from holes which have been worn through the peaty and heathy soil, and they are moved up 
the slope by successive powerful gusts. Further proof of the force of the wind is furnished by the 
number of little pools, ponds, and miniature tarns scattered over the ground above the edge of the 
cliff. The wind, taking advantage of hollows and little gullies or holes worn in the peaty covering by 
runnels formed after heavy rain, tears them wide open. When in dry weather the surface of peat 
becomes loose and powdery, the dust and loose fibres are blown away. This, of course, takes place 
more especially on the sides and bottoms of the hollows, which are thus further widened and deepened. _ 
The return of heavy rain serves to fill these hollows with black or brown peaty water. But the 
denuding influence of the wind does not cease, for the water is thrown into ripples and waves, which, 
beating against the black peaty sides of the pools, loosens them and removes the peat, partly in solution 
and partly in suspension, so as to allow of its being carried away in the outflow. In this manner the 
ground comes tu be covered with shallow ponds and sheets of black water, which remain until they are 
either filled up with decayed peat débris, or emptied by the lowering of their margin at the point of 
exit. 

