I860.] JAMIESON DRIFT, ABERDEEXSniRE. 349 



the river-basins I have examined, decreasing in extent as we ascend 

 their course. 



It is not, however, confined to the neighbourhood of those streams, 

 but also covers many tracts where no river appears to have existed. 



All along the valley of the Dee, from the seaport of Aberdeen to 

 Braemar, which is situated nearly sixty miles into the interior, this 

 upper rolled gravel is everywhere to be found, diminishing, however, 

 greatly in quantity towards the head of the valley. 



At Aberdeen it forms large swelling mounds and Little hills, on 

 which a great part of the city and its suburbs is built. In many 

 places it is spread out in wide horizontal sheets, as at Aboyne, the 

 Moor of Dinnet, Ballater, and elsewhere. Again, it is met with 

 tumbled up in tumultuous hillocks or longitudinal mounds parallel to 

 the strike of the river. But, wherever we find it, it is always clearly 

 distinguishable from the subjacent drift, 1st, by the absence of the 

 striae or glacial hurinage on the pebbles ; 2nd, by the highly water- 

 rolled aspect of the deposit ; and 3rdly, by its looser texture and 

 different hue, — for the drift in this valley is all of a bluish or brown- 

 ish-grey colour, while the gravel is of a ferruginous tint. The junc- 

 tion of the two beds is also in general sharply defined. Nowhere can 

 it be better studied than at the Moor of Dinnet, which is situated 

 about thirty-five miles inland, between the villages of Aboyne and 

 Ballater, and at an altitude of, probably, 600 feet above the sea. 



In some of the sections there, I noticed a feature of this gravel 

 that would seem to indicate the action of a current flowing down the 

 valley, and not a deposition on the beach of a lake or sea-margin ; 

 and as I have not seen this character noticed by any one, some 

 description of it may be useful. 



If the pebbly bed of a rapid-flowing river be examined, it will be 

 found that the stones in it have a tendency to assume a certain 

 position, which is probably that of greatest resistance to the stream. 

 Where the stone is of an oval and flattish form (as most water-worn 

 river pebbles usually are), this position is not horizontal, but deviates 

 therefrom in this respect, that it dips towards the em-rent, thus : — 



Fig. 2. — Position of an ovalpebbU in a stream. 



Consequently, if yon place yourself on a .sheet of Buch pebbles and 

 Look down the stream, you will observe that the stones, as a rule, 



Fig. 3. — Position of oval pebbles in a stream. 



present their sloping bees to the view | fig. '■>) ; whereas if yon reverse 

 your position and Lookup the Btream, you will see their ends pointing 



