I860.] 



JAMTESON DKIFT, ABERDEENSHIRE. 



347 



of the glacier must then have taken place, to leave the space now 

 taken up by the lake ; and then another terminal moraine must have 

 been formed beneath the water, which exists now as the ter- 

 raced deposit at the inner end of the lake. Another shrinking of 

 the glacier would leave the hollow for the second lake (where two 

 exist in the same valley). The terrace -form must have been given 

 as the moraine was gradually upheaved above the water-level. 



The resemblance between these lake-barriers and the ordinary 

 terraced deposits containing recent shells is so strong as to render a 

 more detailed examination and comparison interesting. A practised 

 observer of moraine-deposits woidd perhaps detect the usual charac- 

 teristics ; and if these notes should serve as a point of departure for 

 any such, their end will be attained. 



The river between the lake and the fjord, cutting through the 

 very heart of the deposit, often affords good fishing- quarters ; and on 

 a " blank " day a man might with advantage turn his attention to the 

 banks of the stream, and search for a scratched pebble or other sign 

 of the origin of the debris around him. 



2. On the Drift and Rolled Geavel of the North of Scotland. 

 By T. F. Jamieson, Esq. 



[Communicated by Sir R I. Murchison, F.G.S. &c.] 



Contents. 



1. The Upper Gravel, its distribution 



and origin. 



2. The Marine Drift of the higher 



grounds and Highland glens. 



3. Striated and Polished Rock-surfaces 



beneath the Drift. 



4. High-lying Boidders — dispersion of 



blocks from the Ben Muic Dhui 

 Mountains. 



5. Probability of extensive Glacier- 

 action before the Drift. 



G. Extinction of the Land-fauna pre- 

 ceding the Drift. 



7. Sequence of events during the Plei- 

 stocene period. 



§ 1. In a former communication* I gave an account of some features 

 of the Pleistocene deposits along the coast of Aberdeenshire, showing 

 that in certain localities remains of marine animals occur of a cha- 

 racter similar to those met with in the later tertiary beds of the 

 Clyde district, and, like them, indicating the presence of a colder sea. 

 The following pages are devoted chiefly to the Drift of the interior of 

 the country and of the higher grounds, more especially as regards 

 that part of Scotland lying between the Moray Firth and the Firth 

 of Tay. 



In the lower parts of this district we find the drift-lied- and brick- 

 clays covered by a widespread accumulation <>f water-rolled gravel, 

 often of great thickness and destitute of fossils. It [spovffed out in 

 greatest profusion towards the mouths of valleys, and pervades all 



* Quart. Jonni. QfloL Boo. vol. xiv. |> 509 



2 i. 2 



