Messrs Peach and Home on the Glaciation of Caithness. 33S 



and from thence it forms a series of bluff cliffs, from 20 to 

 25 feet in height, as far as the rocky ravine below Dirlot 

 Castle. In these sections we detected numerous blocks of 

 secondary rocks, with fragments of marine shells. 



In the burn of Isauld, and by the roadside leading to 

 Shebster, sections of red boulder clay, free from shells and 

 secondary rocks, are found resting on the grey flagstones. 

 Associated with pieces of the grey flags are numerous striated 

 blocks of red sandy flags and grits. A slight knowledge of 

 the geological structure of the district satisfactorily explains 

 the overlap of the red boulder clay on the grey flagstones 

 east of Eeay. On the hiUs round Ben Eah, and southwards 

 to Loch Scye, there is a coarse granitic breccia, largely com- 

 posed of fragments of orthoclase felspar. In the upper reaches 

 of the Forss Water this granitic breccia passes underneath a 

 great series of chocolate- coloured flags, which cover a strip 

 of G^round a mile in breadth between Achsteenalate and the 

 east bank of Loch Shurrery, and these beds are overlaid in 

 turn by the grey flagstones of Ben D orrery. Now, the local 

 ice, which streamed north-east and north from the hilly 

 ground between Ben Eah and Ben Shurrery, must have 

 crossed these zones at the base of the Old Eed Sandstone; 

 and hence numerous blocks of the chocolate flags would be 

 mingled with the ground moraine, and the colour of the 

 deposit would naturally become red. In its northward march 

 this local ice must have invaded the area occupied by the 

 grey flagstones between the burn of Isauld and Shebster. It 

 is not necessary, therefore, to invoke a movement from the 

 north-west to explain this overlap. In the light of the 

 foregoing facts, all difficulty regarding its occurrence dis- 

 appears. 



To the west of Sandside Lodge, by the roadside, there is 

 a section of similar reddish-brown boulder clay of local origin, 

 containing blocks of grey micaceous gneiss, granite, pink 

 felstone, grey and red flags. 



To the east of the line already described, as marking the 

 inland limit of the shelly drift, the boulder clay differs widely 

 in character from that just described. The shelly drift is 

 not distributed uniformly over the whole area. It reaches 



