NICOL SOUTHERN GEAMPIANS. 197 



A similar relation occurs at the extreme north-east termination of 

 the chain between Stonehaven and Aberdeen, in the section on the 

 sea-coast described by me in a paper formerly read to the Society*. 

 Referring to it for further details, I shall now make a few general 

 remarks on the sections described. 



14. Relation of the Old Red Sandstone. — The first point I would 

 notice is the relation of the Old Red Sandstone to the primary or 

 metamorphic strata. Some years ago I showed that in Cantyre the 

 Eed Sandstone rests conformably on the mica-slate t, and has, in part 

 at least, been elevated along with it. It is therefore not improbable 

 that these deposits are among the oldest unaltered red conglomerates, 

 and distinct from other red sandstones that rest on them. On the 

 mainland from Loch Lomond to Stonehaven the sandstones are sepa- 

 rated from the slates by a great line of fault ; and I do not remember 

 any place where the sandstones are seen resting immediately on the 

 older rocks. "Very often, as in the Comrie section, a great intrusion 

 of trap intervenes, and, though less marked in other localities, a 

 band of igneous rock might probably be traced almost continuously 

 from sea to sea. Near the line of junction the sandstone has been 

 forced up at a high angle, and dips away from the primary strata. 

 It is often a hard, coarse conglomerate, but mixed with finer beds, 

 and in many places forms a range of lower hills skirting the great 

 Grampian chain. The position of the sandstone implies that the 

 strata forming the primary mountains on the north have not merely 

 been elevated, but have undergone a great lateral expansion, or push- 

 ing out to the south-east %. 



15. Clay-slate and Mica-slate. — The relation of the clay-slate to 

 the mica-slate is more complex and difficult of explanation. In Can- 

 tyre clay-slate does not appear, having, as it were, been split off from 

 the mica-slate by the granite -eruption of Goatfell, in Arran. Further 

 north-east, as formerly stated, the two formations run side by side 

 along the whole southern base of the Grampians. But in Bute and 

 on the Garelochboth formations dip S.E., and the clay-slate rests on 

 the mica-slate almost or altogether conformably, and at low or 

 moderate angles. On Loch Lomond the two formations are nearly 

 vertical, but both have still a southerly inclination, so that the clay- 

 slate continues to rest on the mica- slate. At Callander both forma- 

 tions dip north, and now the clay-slate apparently below the mica- 

 slate. At Comrie the two formations are unconformable, and both, 

 perhaps from the intrusion of the syenite, have a strike oblique to 

 their ordinary course. At Dunkeld, Blairgowrie, and other places, to 

 Stonehaven, the clay- slate again dips north, towards, and apparently 

 under, the mica-slate. There is thus a most remarkable anomaly 

 in the two portions of the chain. The clay-slate, which at the 

 western extremity covers the mica-slate, and is thus the newer for- 

 mation, is at the eastern end covered by it, and is there apparently 



* Quart. Journ. Geol. Soc. vol. xi. (1855) p. 544. 



t Nicol, on Geology of Cantyre, Quart. Journ. Geol. Soc. vol. viii. (1852) 

 p. 410. 



X Nicol, on Eastern Grampians, Quart. Journ. Geol. Soc. (1858) vol. xi. p. 549. 



