1873.] JTJDD — THE SECONDARY ROCKS OF SCOTLAND. 185 



membered that no portion of the Secondary series in the north of 

 Europe has been almost everywhere so extensively removed by de- 

 nudation as the Neocomian. From the wide-spread mid-Cretaceous 

 denudation, marking a period of upheaval which preceded that great 

 subsidence during which the littoral Tipper Greensand and Gault, 

 and the abysmal Chalk were deposited, no beds have so greatly 

 suffered as the Neocomian, which were, at the period of that great 

 denudation, the youngest and most recently formed. The proofs of 

 this denudation are familiar to all geologists in the Tourtia of Belgium, 

 the Cambridge Greensand and the Hunstanton Limestone of England; 

 and in a subsequent portion of this memoir I shall have to show what 

 beautiful illustrations of the same great movements are exhibited by 

 the Cretaceous strata of the west coast of Scotland, and in some of 

 the adjoining Hebridean Islands. 



While, therefore, we remember the fact that in the Worth-Euro- 

 pean district the Neocomian strata, as compared with those of 

 Jurassic age, were originally deposited over more limited areas of 

 sea-bottom, the circumstance of the greater amount of destruction 

 by denudation to which the former, as compared with the latter, have 

 been subjected, should not be lost sight of. The first of these 

 considerations, taken in combination with the fact of the compara- 

 tive rarity of fragments of Neocomian strata in the Scottish drifts, 

 might lead us to decide against the probability of rocks of that age 

 having ever been deposited in the district ; if, however, due weight 

 be allowed to the second circumstance alluded to, the geologist will 

 hesitate before he accepts as conclusively demonstrated the former 

 absence of the Neocomian beds in a district where even the Jurassic 

 formations have so narrowly, and through such remarkable accidents, 

 escaped total extinction by denudation. 



§ 10. The Upper Cretaceous. 



No such doubt as that which, as we have admitted, still remains 

 concerning the former presence of Neocornian strata in the east of 

 Scotland can be said to exist and to interfere with our adoption of 

 the conclusion that the same area was once covered by strata of the 

 Upper Greensand and Chalk. Although no Upper Cretaceous strata 

 can be detected in situ in the north-east of Scotland, yet the vast 

 abundance of the relics of these beds, bearing certificates of their 

 age in their included fossils, which abound in the Boulder-clays of 

 Aberdeenshire, Banffshire, Sutherland, Caithness, and the other 

 counties in the north-east of Scotland, raises the very strongest sus- 

 picion that, at a period as recent as the Glacial epoch, great deposits 

 of the Upper Cretaceous still remained unremoved, and supplied 

 numerous boulders to the Till. But when we reflect on what have 

 now been shown to be the relations of the Greensand and Chalk to 

 the other Secondary rocks, alike in Southern Sweden, Western Scot- 

 land, the Hebrides, and the north of Ireland, the strong conviction 

 just referred to is converted into something very like certainty. 



That in several parts of the county of Aberdeen enormous quan- 



