162 proceedings of the geological society. [jail. 11, 



§ 1. Intkodijction. 



At the end of a paper forwarded to tiie Society in December 1859, 

 and printed in the 16th volume of the Quarterly Journal, I gave a 

 -Concise oiitline of what seemed to me to have been the geological 

 history of Scotland since the commencement of the glacial period. 

 Hhe following pages are devoted to a further illustration of this 

 subject. The facts on which I rest my conclusions are derived 

 from the midland region of Scotland, chiefly from the part lying 

 between the Moray Firth and the Firth of Forth. This district 

 seems to me to contain remarkably good evidence of the changes 

 that have taken place, and these changes, I believe, have been 

 general over the greater part of Britain. 



§ 2. Peeglacial Teaces. 



The absence of the later Tertiary strata in Scotland leaves us in 

 the dark as to the state of things that ushered in the glacial period 

 in that country. There are, however, on the eastern coast of Aber- 

 deenshire, in the parishes of Slains and Cruden, some thick masses 

 of sand and gravel which appear to be of Tertiary age, and are pro- 

 bably equivalent to the Eed Crag of England. These beds, in some 

 places, contain remains of shells evidently belonging to a consider- 

 able number of species, but so broken and worn that in the great 

 majority of cases it is impossible to arrive at a satisfactory deter- 

 mination of their specific character. Nevertheless I have got 

 enough now collected to enable me to see that they form a 

 group very distinct from those met with in our glacial beds, and 

 more resembling what are found in the Crag strata of England. 

 Some of them are of species that seem to be extinct. There are 

 fragments of Voluta Lamberti, Cyprina rustica, Nucula Cohholdice, 

 Fusus contrarius, Purpura incrassata, Nassa elegans, Wassa reticosa, 

 Turritella incrassata, and probably Troplion costiferum,- — forms un- 

 known either in our glacial beds or in our present sea. Besides these 

 there are the broken remains of many others, of the genera Car- 

 dium, Pecten, Venus, and Astarte, which differ from those found in 

 any of our glacial beds ; and one of the most common shells is the 

 Pectunculus glydmeris, which attained a large size. 



The position of the sand and gravel containing these shells also 

 leads^me to think them preglacial. So far as I have seen, no 

 Boulder-clay occurs below them, neither does the rock on which 

 they rest exhibit any appearance of glaciation, nor do the pebbles 

 show any glacial scratches. This Crag-gravel ranges up to about 

 200 feet above the present sea-level, and is covered in many places 

 by red clay of the glacial period, containing large boulders and ice- 

 scratched stones. Along its landward margin the gravel is fre- 

 quently thrown into abrupt and irregular mounds, more especially 

 at its south-western border, near the Loch of Slains * ; and this I 

 Jim disposed to attribute to the pressure of the land-ice during the 



* See Quart. Journ.,Geol. Soc. vol. xiv. p. 522. 



