116 PEOCEEDn^GS OF TKE GEOLOGICAL SOCIETY. [Jline 9, 



Easdale, and, so far as I noted them, apparently corresponding 



both in mineral character and relative age. One group were grey 



claystones, running nearly W.S.W. and intersected by other veins 



of dark greenstone, occasionally amygdaloidal, with a N.W. direction 



(N. 48° "W.). In this place both sets of veins intersect liassic 



strata containing characteristic Ammonites and Gryphcece, and are 



thus shown to be of more recent date than these deposits. It thus 



appears that, subsequent to the Jurassic period, this region of 



Scotland has been rent by two distinct sets of fissures, one nearly 



parallel to the stratification, the other at right angles to the first 



and also to the bedding of the rock. Considering the trap-rocks of 



Airdnamurchan, Mull, and Lorn as one mass, the second line is 



nearly parallel to its longer axis, and also to the Sound of Mull; 



but I am inclined to regard these veins as more recent than the 



great body of overlying trap in this region. In truth, one of the 



most striking facts forced on the geologist in examining this portion 



of Scotland, is the conviction of the very recent date of many of the 



great convulsions by which its present physical outline has been 



produced. Thus, the mountain-cliiF (1200 to 1500 feet high) forming 



the coast of Morven, between Ardtomish and the Linnhe Loch, 



consists half of the old gneiss, half of liassic strata and recent 



trap, brought side by side with each other along an enormous fault, 



and now smoothed down into one uniform mass. 



Conclusion. — In conclusion, it might be expected that I should 

 notice the probable age, and equivalents in other parts of the country, 

 of the slate-rocks. They are, however, such a mere fragment, so 

 broken up, and so unconnected with other stratified deposits, that 

 little more than conjecture could be ofiered. I have been in the 

 habit of identifying these slates with the band of clay-slate on the 

 southern margin of the Grampians, which I have long considered to 

 be the equivalent of the Lower Silurian slates of the south of Scot- 

 land. At present I am rather disposed to regard the Easdale and 

 Oban slates as a higher and more recent deposit than the slates of 

 Bimam and Dunkeld, although, as stated above, both the obscure 

 traces of organic remains and the mineral character of the rocks 

 might lead us to identify them with the Skiddaw slates of Professor 

 Sedgwick, and thus with some of the lowest beds of the Palseozoic 

 series. Near Oban they are covered unconformably by great masses 

 of conglomerate and red sandstone, in their turn overlaid by trap ; 

 but the age of these beds is, perhaps, even more uncertain than that 

 of the slates. They are usually classed as Old Red Sandstone, on 

 the same ground that all the red sandstones and conglomerates of 

 Scotland have been put into this category, but, it seems to me, 

 without any good reason*. To discuss the age of these rocks would, 

 however, lead into questions involving the structure of the whole 

 north and west of Scotland, and thus quite beyond the object of the 

 present communication. 



* In my recent Greological Map of Scotland, I have classed these beds as 

 being probably Trias, — the commencement of the Mesozoic series of the west 

 coast. — J. N., January 1859. 



