Geological Society of London. 



141 



covered with thousands of feet of Secondary deposits. Hence it 

 appears that an enormous amount of denudation has gone on in the 

 Highlands during Tertiary times, and that the present features of 

 the area must have been, speaking geologically, of comparatively 

 recent production — most of them, indeed, appearing to be referable 

 to the Pliocene epoch. 



The alternation of estuarine with marine conditions, which had, 

 on a former occasion, been proved to constitute so marked a feature 

 in the Jurassic deposits of the Eastern Highlands, is now shown to 

 be almost equally striking in the Western area ; and it is moreover 

 pointed out that the same evidence of the proximity of an old shore- 

 line is exhibited by the series of Cretaceous strata in the West. 



The succession and relations to one another of the series of de- 

 posits, now described as occurring in the Western Highlands, is 

 • given in the following Table : — 



Miocene Volcanic and Intervolcanie Socks. 



Unconformity. 



13 i 

 I 



1. Estuarine clays and sands with coal 



2. White Chalk with flints (Zone of Beletmiitella inucronata) ... 



3. Estuarine Sandstones with coal 



4. Upper Greensand heds 



Maximum 

 thicknesses, 

 feet. 

 20+ 

 .. lO-f 



.. 100 

 60 



Unconformity. 





5. Oxford clay 



6. Great Estuarine Series 



7. Lower Oolite 



8. Upper Lias 



9. Middle Lias 



10. Lower Lias 



11. Infralias 



12. Poikilitic 



1000 



400 



100 



500 



400 



200 

 1000-f 



Unconformity ? 



Carboniferous strata (Coal-measures). 



Unconformity. 



Old Gneiss Series and Torridon Sandstones. 



Although no traces of the Upper Oolite or the Neocomian forma- 

 tions have as yet been detected in the Western Highlands, yet it is 

 argued that when we consider how enormous has been the amount 

 of denudation, and how singular the accidents to which all the ex- 

 isting relics of the Secondary period have owed their escape from 

 total destruction, we cannot but regard it as a most rash and 

 unwarrantable inference to conclude that no deposits belonging to 

 those periods were ever accumulated within the district under con- 

 sideration. 



The Carboniferous strata of the Western Highlands have been 

 detected at but a single locality ; and even there, being exposed in 

 a series of shore reefs that are only occasionally well displayed, 

 can only be studied under favourable conditions of tide and wind. 



