262 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Feb. 7, 



under which the beds containing them had been accumulated, and 

 to compare them with those of other districts with which I was 

 already acquainted. 



In the neighbourhood of Glasgow, and along the east coast from 

 Aberdeen to Edinburgh, we find the beds containing Arctic shells 

 lying on the top of a rough boulder- clay destitute of such fossils ; 

 and these marine fossiliferous beds are often of great depth and 

 finely laminated, presenting all the features of tranquil and regular 

 deposition. The remains of mollusca and starfishes in them are, in 

 many instances, quite entire and uninjured, as if they had been gra- 

 dually enveloped in the fine mud in which the animals lived and 

 died, while the crust of large barnacles on some of the stones points 

 to a like stillness of the sea-bottom. In Caithness nothing of this 

 sort has been observed ; no distinction has been made of a rough 

 boulder- clay destitute of fossils and an overlying marine fossiliferous 

 bed; the shells, according to all observers — Dick, Cleghorn, Hugh 

 Miller, Peach, and others — are described as being scattered in a 

 broken state all through a mass of rough boulder-clay, and no such 

 thing as a bed of tranquilly deposited marine sediment containing 

 entire shells has been reported. This seemed to me to indicate 

 that the conditions under which the glacial beds of Caithness were 

 accumulated must have differed in some way from those that pre- 

 vailed in the other districts, and I was therefore desirous of studying 

 the locality in order to make out, if I could, the cause of the 

 diiference. 



2. General distribution of the Drift, its colour, texture, and contents, — 

 Yiewed from a distance, Caithness has the appearance of a bare 

 undulating plain, sloping very gently to the north and north-east, 

 and terminating in hues of rocky cHJff which are battered by a rest- 

 less and stormy sea. Along the southern border of this plain there 

 is a fine group of hills, of which Morven (2331 feet), the Scarabins 

 (2048 feet), and the Pap of Caithness (1229 feet) are the most con- 

 spicuous ; there are, also, some straggling heights of lesser impor- 

 tance along the western side of the county. These hills form a sort 

 of separation or boundary between the low district of Caithness and 

 the more mountainous region of Sutherlandshire. Geologically it is 

 a country of Old Red Sandstone. The hills just mentioned consist 

 of quartzose mica-schist and granite, on the flanks of which repose 

 thick masses of conglomerate and grit forming the base of the Old 

 Red in this region. These beds of conglomerate and grit pass up 

 into a great series of thin-bedded shales, flags, and sandstones, gene- 

 rally of a dark-grey colour, which stretch away in billowy undulations 

 over the surface of the country to its north-eastern corner, as has 

 been well shown by Sir Eoderick Murchison. 



It is in the low troughs and winding hollows which form the 

 beds of the various streams that we find any quantity of glacial 

 debris ; on the higher ground the rocks are either bare and devoid 

 of earthy cover, or hidden by a growth of peat and heather. Some 

 of these low tracts run across the country from side to side, as, for 

 example, from "Wick to Thurso by way of Loch Watten, and between 



