J. W. JtTDD ON THE SECONDARY ROCKS OF SCOTLAND, 693 



out any very clear order of succession among the beds or to estimate 

 their total thickness with any approach to accuracy. 



The same remark applies almost equally to the section on the 

 south side of the Ardnamurchan peninsula, to the east of Mingary 

 Castle. Here it is evident that beds of breccia and conglomerate, 

 made up of gneiss, quartzite, and limestone pebbles, and often having 

 a calcareous matrix, are interposed between the old gneiss rocks and 

 the here greatly metamorphosed Infralias limestones. But neither 

 in the coast-section nor in the exposures of the same strata inland, in 

 the interval between them is it possible to obtain any satisfactory 

 order of succession or correlation of beds, where all have been sub- 

 jected to such violent subterranean movements, igneous intrusion, 

 and profound metamorphism in consequence of the proximity of the 

 great Miocene volcanic centre of Ardnamurchan, and the long sub- 

 sequent action of the far inferior but by no means insignificant 

 igneous extrusions of Beinn Shiant. 



In Morvern the Poikilitic strata evidently attain in places con- 

 siderable thickness and importance ; but both the order of succession 

 of beds and the degree of development of the whole mass exhibit 

 most wonderful diversities within very short distances. 



Around Loch Arienas, under three of the great outlying patches 

 of basalt that lie on the north side of that lake and the arm of the 

 sea called Loch Teachdaish, and again near the head of Loch Aline 

 and at the base of the cliffs of Ardtornish, we everywhere find the 

 variegated sandstones and marls, the calcareo-siliceous rocks, the 

 coarse conglomerates and breccias, so characteristic of this series of 

 deposits. At Ardtornish Towers is a rather deep quarry in the 

 coarse and conglomeratic sandstone of pink and greenish tint, al- 

 most wholly made up of quartz pebbles. This quarry is remarkable 

 as having afforded the only traces of fossils of the Hebridean 

 Poikilitic strata; and these are, as we have seen, of the most imper- 

 fect character. The conglomeratic sandstones of Ardtornish Towers, 

 of which some 50 or 60 feet are exposed, though the bottom is not 

 reached, are covered by beds of red and white clays and sands, with 

 masses and layers of concretionary limestone, strikingly similar in 

 character to the cherty rock of Stotfield. 



It would be of little service to give details of the numerous small 

 exposures of these very variable strata. Suffice it to say that every- 

 where in Morvern we find the general order of succession to be (from 

 above downwards) : — 



(1) Red, green, grey, and variegated sands and sandy marls. 



(2) Concretionary limestones, sometimes of considerable thickness. 



(3) Eed marls and some sandy beds. 



(4) Coarse conglomerates, grits, and sandstones, with breccias at the base. 



We may further remark that the thickness of these several 

 members is most inconstant, the total varying from a few feet only 

 in Beinn-y-Hattan to about 200 feet near Kinloch Aline, and 400 

 or 500 feet at the Innimore of Ardtornish. 



Wherever the Poikilitic series is complete in Morvern it is covered 



