672 JAMES GEIKIE 



The deposits of the 45-50 foot beach immediately covering the 

 peat are crowded, especially toward the base, with leaves, branches 

 and twigs of the trees just mentioned. When these estuarine accu- 

 mulations are followed up the Tay valley, they gradually become 

 more and more arenaceous, until eventually they merge into ordinary 

 river alluvia — the materials of which become increasingly coarser 

 as they approach the mountains. 



It is worthy of note that the 45-50 foot beach often fails to appear 

 at the heads of particular fiords in the west Highlands, although 

 it may be well developed in their lower reaches. This is explained 

 by supposing that glaciers may have occupied the upper ends of 

 such fiords during the depression of the land — an inference much 

 strengthened by the fact that at the head of Loch Torridon, where 

 the beach in question is well seen, it is capped by conspicuous ter- 

 minal moraines. This evidence, so far as it goes, leads to the con- 

 clusion that the more important phenomena characteristic of the 

 100 foot beach, were repeated — but on a smaller scale, and in a 

 less pronounced degree — in the case of the 45-50 foot beach. In 

 a word, we are forced to believe that during the formation of the 

 latter snow-fields and glaciers existed in the Highlands. 



The latest conspicuous raised beach is that occurring at an average 

 level of 25 to 30 feet above the sea. The only shells it has yielded 

 belong to still indigenous species. Nowhere, so far as known, do 

 the deposits of this beach merge inland into fiuvio-glacial gravels, 

 nor does the beach appear to be anywhere associated with moraines. 

 It frequently contains drifted stools and trunks of pine and other 

 trees of large size. Now and again also we find it resting directly 

 upon peat with trunks and stools of trees rooted in an underlying 

 soil. It is often hard to say, however, whether these ancient land- 

 surfaces may not sometimes be on the same geological horizon as 

 the peat that underlies the deposits of the 45-50 foot beach. 



PEAT-MOSSES 



Postponing for the present any further remarks on the evidence 

 supplied by our so-called postglacial raised beaches, I would shortly 

 direct attention to certain other accumulations, which indubitably 

 belong to later times than the closing stage of the Glacial Period, 



