BRITISH POSTGLACIAL 6- RECENT DEPOSITS 411 



other rivers, and the raised-beaches of the more open coasts, 

 demonstrate a subsequent general submergence of the land to a 

 depth below its present level of about 50 feet ; and they like- 

 wise afford more or less striking indications of a climatic change 

 from genial to less genial conditions. I have given my reasons 

 for believing that much of the clay in the older Carse-deposits is 

 of glacial origin, and consists of the fine mud and silt carried 

 down by turbid rivers, the upper reaches of whose valleys were 

 occupied by local glaciers. This, however, is not the only evi- 

 dence we have of glacial action at the time the sea stood at the 

 45-50-feet level. In many of the Highland sea-lochs glaciers 

 would appear to have come down to the sea and calved their 

 icebergs there ; and this is probably the reason why the 45-50- 

 feet beach is not often well seen at the heads of such sea-lochs. 

 The glaciers seem in many cases to have flowed on for some 

 distance into the sea, and so prevented the formation of a beach 

 and cliff-line. In other cases, however, they appear to have 

 thrown down their moraines as soon as they reached the sea. 

 A very good example of this occurs at the mouth of Glen Brora 

 in Sutherland, where well-marked moraines and morainic gravel 

 with large blocks are found resting upon and apparently of the 

 same age as the deposits of the raised-beach. When the High- 

 land valleys of the west coast come to be examined more 

 attentively by geologists, I have no doubt that similar appear- 

 ances will be discovered in many places. The moraines of the 

 old glacier of Glen Messan (Argyleshire), described long ago by 

 Charles Maclaren, 1 come down to within 40 feet or less of the 

 present sea-level, and, according to Eobert Chambers, 2 morainic 

 detritus rests upon the 30-feet beach at the opening of Glen 

 Iorsa in Arran. 



The general fresh appearance of roches moutonndes and striae 

 in many Highland glens, and the fine state of preservation of 

 the valley-moraines, have often been adduced as proof that the 



1 Brit. Assoc. Rep., 1850, p. 90; Edin. New Phil. Journal, New Series, 1855, 

 vol. i. p. 189. 



2 Brit. Assoc. Rep., 1854, Trans, of Sections, p. 78 ; Edin. New Phil. Jour., 

 New Series, vol. i. p. 103. 



