36 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 19, 



great metamorphic action, which seems to have less affected the 

 upper portion of the red sandstone ; whilst the bottom beds of the 

 sandstone again, as on the Gairloch, have been exposed to it in a 

 much higher degree. In other words, the red sandstone and quartzite 

 appear to have been more affected at the two extremities, above and 

 below, than in the middle of the series*. 



Probable Age. — On the whole, therefore, though all doubt can only 

 be removed by the discovery of better-preserved characteristic fossils, 

 I regard the theory, that the red sandstones of the West Highlands are 

 of Devonian age, the quartzite and limestone of Lower Carboniferous, 

 as the more probable. Whether we consider the gneiss resting on 

 the latter as a newer metamorphic group, or merely as a portion of 

 the lower gneiss forced up over it in some great convulsion, we have 

 still views of very great interest opened up to us in the history of 

 these Highland mountains. They can no longer claim that remote 

 geological antiquity which has hitherto been assigned to them, but 

 belong, at least in their present form, to a far more recent period in 

 the history of the earth, — to one posterior to the deposition of the 

 horizontal coal-fields and sandstones of the south. 



In offering to the Society, first a statement of facts, and then my 

 views of the probable age of the quartzites and limestones, I wish it, 

 however, to be understood that my Memoir has reference only to the 

 north-west coast of Scotland, How far it may apply to the quartzites 

 of other parts of the Highlands must be left to future consideration. 

 It is also clear, that these facts in no way affect the accuracy of the 

 Devonian classification of the great ascending triple series of the east 

 coast, — of the coarse conglomerates and red sandstones, the dark 

 bituminous Caithness flags, and the overlying red sandstones of 

 Dunnet Head and the Orkneys, — as established by Sedgwick and 

 Murchison in their most important memoir. I am fully convinced 

 that Scotland contains red sandstones and conglomerates of various 

 dates ; and should it ultimately prove that the quartzite and lime- 

 stones now under consideration are of Silurian age, I shall deem it 

 no small matter to have established, as the facts now stated would 

 then clearly prove, that the red sandstones of the west coast belong 

 to a far different period from the corresponding rocks on the east, 

 with which they have hitherto been identified. 



Geological History of the North-ivestern District of Scotland. — 

 Before concluding, there are a few considerations on the succession 



* I have not referred in the text to Mr. Hugh Miller's views of the age of these 

 beds, as I am not aware he has ever fully published them, except in an article in 

 the * Witness' newspaper printed before the discovery of the fossils by Mr. Peach. 

 He appears to consider the whole as Devonian, — the red sandstones representing 

 the lower conglomerate, the limestone the middle calcareo-bituminous flags of 

 Caithness, and the quartzite the upper red sandstones of Dunnet Head. My rea- 

 sons for not adopting this classification will be readily suggested by the text. [The 

 lamented death of this distinguished geologist offers another reason for not con- 

 troverting a theory which he is no longer spared to defend. — J. N. January, 1857.] 



