﻿1861.] 



HARKNESS HIGHLANDS AND N. IRELAND. 



267 



ment of the rocks seen between this locality and Appin. At Port 

 Appin thick masses of quartz-rocks are seen, which are greatly con- 

 torted, having a prevailing S.E. dip. These are succeeded con- 

 formably by dark slates ; and the arrangement here represents the 

 N.W. end of the Ardsheal section. 



The limestone islands which occur in Loch Linnhe exhibit cal- 

 careous strata in great development. In Sheep's Island these lime- 

 stones are much contorted, and very nearly perpendicular, but with 

 a predominant S.E. dip. Judging from this, we might be induced to 

 infer that the strata here pass under the quartz-rocks of Port Appin ; 

 and if this be the case, they represent a zone of calcareous rocks 

 altogether different from that previously alluded to, and, under such 

 circumstances, they must be regarded as the equivalents of the thick 

 limestones of Assynt. But perhaps it may be premature to arrive at 

 this conclusion without more evidence than that at present afforded 

 by the sections on this coast. 



The sections which the districts lying N.W. of the area of quartz- 

 rocks and limestones already referred to exhibit show, with probably 

 the exception of the islands in Loch Linnhe, a sequence of stratified 

 deposits very nearly allied to that which the region S. of this zone 

 manifests. Quartz-rocks at the base, succeeded conformably by 

 limestones, and these by gneissose or dark slaty rocks, make up the 

 stratified beds N.W- of the zone of " quartz-rocks and limestones " 

 which extend from Jura to the K.E. coast of Scotland. The rocks 

 in the areas separated by this zone represent each other in arrange- 

 ment and almost in mineral nature, — the only difference being in the 

 character of the highest member, which occurs as a blackish slate 

 on the west coast, while toAvards the south-east its equivalent has a 

 gneissose aspect. This conclusion, as to similarity in age and position 

 among the deposits south of the Caledonian Canal, supposes the ex- 

 istence of a great line of fault traversing tbe Grampians in a S.W. 

 and N.E. direction ; and tbis line of fault — parallel to the great 

 S.W. and N.E. fault along the southern margin of this range of 

 mountains separating the metamorphic rocks on the N.W. from the 

 Old Eed Sandstone series on the S.E., extending from sea to sea — is 

 well seen in Glen Lyon along the northern edge of the quartz-rocks. 

 On the N. of this line of fault we have a great downthrow, the 

 higher beds of the series (the gneissose rocks) being again repeated ; 

 and as we approach the N.W. coast of Argyllshire, we have the 

 lower members (the limestones and quartz-rock) again brought to 

 the surface by the agency of plutonic masses. 



With reference to the relations which these quartz-rocks, lime- 

 stones, and gneissose strata, constituting so much of the great mass 

 of the Grampians, bear to other rocks of a similar nature in the 

 N.W. and N. of Scotland, I cannot better illustrate this than by 

 referring to Sir Roderick Murchison's " Section across Locbs Eriboll 

 and Hope*." In this section the upper quartz-rocks, upper lime- 

 stone, micaceous and quartzose flagstones, and micaceous and gneissose 

 flagstones represent the series of strata which form the Grampians S. 

 * Quart. Journ. Greol. Soc, vol. xvi. p. 226. 



