316 Geological Society. 



marine series alternating with two others of estuarine origin. At 

 the base we find marine deposits of Upper Greensand age, strikingly 

 similar to those of Antrim, bnt in places passing into conglomerates 

 along old shore-lines. Above the Upper Greensand beds occur 

 unfossiliferous sandstones, in which thin coal-seams have been 

 detected ; and these are in turn covered by strata of chalk, converted 

 into a siliceous rock, but still retaining in its casts of fossils (Belem- 

 nitella, Inoceramus, Spondylus, &c), and in its beautifully preserved 

 microscopic organisms (Foraminifera, Xanthidia, &c.) unmistakable 

 proofs of its age and the conditions of its deposition. Above this 

 representative of the highest member of the English Chalk there 

 occur argillaceous strata with coal seams and plant-remains which 

 are perhaps the equivalent of younger members of the Cretaceous 

 series, not elsewhere found in our islands ; or, it may be, they must 

 be regarded as belonging to periods intermediate between the Cre- 

 taceous and Tertiary epochs. It is greatly to be regretted that 

 these Cretaceous deposits of the "Western Highlands are so un- 

 favourably displayed for our study as to present scarcely any faci- 

 lities for the collection of their fossils ; for these, if found, might be 

 expected to throw a flood of light on some of the most obscure 

 paheontological problems of the present day. 



Although the comparison and correlation of the Secondary strata 

 of the Highlands with those of other areas, and the discussion of 

 the questions of ancient Physical Geography thereby suggested, are 

 reserved for the fourth and concluding part of his memoir, the 

 author takes the opportunity of making reference, in bringing the 

 present section of his work to a close, to several problems on 

 which the phenomena now described appear to throw important 

 light. In opposition to a recent speculation, which would bring 

 into actual continuity the present bed of the Atlantic and the old 

 Chalk strata of our island, he points to the estuarine strata of 

 the Hebrides as demonstrating the presence of land in that area 

 during the Cretaceous epoch. He also remarks on the singular 

 agreement of the conditions of deposition of both the Silurian and 

 Cretaceous strata of the Scottish Highlands and those of the North- 

 American continent. But he more especially insists on the proofs 

 which we now have that the Highlands of Scotland, as well 

 as the greater part of the remainder of the British Islands, were 

 once covered by great deposits of Secondary strata, and that the 

 area has been subjected to enormous and oft-repeated denudation. 

 He dwells on the evidence of the vast quantities of material which 

 have been removed subsequently to the Mesozoic and even to the 

 Miocene period ; and he maintains the conclusion that many, if not 

 all, of the great surface-features of the Highlands must have been 

 produced during the very latest division of the Tertiary epoch, 

 namely the Pliocene. 



