QUATERNARY DEPOSITS OF BRITISH ISLES — BROOKS. 323 



south. At Cleongart bores were put down showing the continuous 

 horizontal extension of the clay for at least 100 yards, and the com- 

 mittee consider that the bed probably extends more or less continu- 

 ously from one glen to another. The top of the clay is from 130 to 

 190 feet above the sea. The Mollusca are northern and much broken ; 

 some of them also extend southward, and most are still British. The 

 Foraminifera are in many cases southern. Here also Munthe con- 

 cluded that the organisms from the center of the deposit are of 

 warmer types than those from the top and bottom. 



After the last general glaciation of Scotland there appear to have 

 been local developments of glaciers of decreasing importance. A 

 summary of his investigations in this connection was given by J. 

 Geikie in 1906 and again in 1914 (99). After the melting of the ice 

 of the last mer de glace, the land sank about 100 feet, and there was 

 a recurrence of glacial conditions, forming piedmont ice sheets in 

 the north and large valley glaciers in the south. The sea lochs of 

 the north were largely occupied by glaciers, which calved and 

 dropped blocks in the 100-foot raised beach. The fauna of this 

 beach is arctic. Outside the region occupied by the glaciers in the 

 south, the lowest layer of the peat bogs is an artic plant bed with' 

 Betula nana, Scdkc polaris, and Dt^yas octopetala. The level of the 

 beach reaches 130 feet in Forfarshire ; from this height it diminishes 

 to less than 100 feet. 



These deposits are considered by Geikie to represent a complete 

 glacial period, his Mecklenburgian, separated from the last mer de 

 glace by an interglacial, but I can not discover any reference to 

 interglacial deposits which can be referred to this period, though 

 conditions should have been favorable for their preservation. It 

 seems more probable that the moraines and the arctic plant beds 

 represent the concluding stages of the last mer de glace. 



This submergence and glaciation were followed by an elevation 

 to above present level, during which considerable peat deposits were 

 formed. At the base is a forest layer with Betula alba; above this is 

 Sphagnum* peat. In many cases, according to Jamieson, these 

 peat beds rest on marl beds containing skeletons of Cervus magaceros 

 and Bos primigenius. During this period the thick and extensive 

 accumulations of the 100-foot beach were largely removed by the 

 rivers. Alluvial flats were formed at lower levels, on which thick 

 layers of woody peat were formed at and below present sea level. 



Renewed subsidence brought about the formation of the 45 to 50 

 foot beach, which in places directly overlies the alluvial peat just 

 mentioned ; moreover, the bottom of this beach is often crowded with 

 leaves, twigs, branches, and occasional trunks of oak, alder, hazel 

 and birch. In the river estuaries the Carse clays were formed. At 

 the head of Loch Torridon well-formed terminal moraines rest di- 



