388 C. CALLAWAY ON THE NEWEK GKEISSIC 



brecciated, and a fault evidently intervenes. A little further west 

 marble appears not far from quartzite, and again near the high road ; 

 but in neither case are the rocks in contact. Near the farm of Loyne, 

 on the north side of the river, marble dipping north-east is over]ain 

 by igneous rock ; and 100 yards to the west is dolomite with a low 

 easterly dip. Round Ledbeg, marble, quartzite, and dolomite occur in 

 several patches ; but, so far as I have seen, there is always a break 

 between the marble and the other rocks. On the slopes to the west the 

 marble displays Eozoonic structure (No. 106, p. 419), first observed 

 by Prof. Heddle. Quartzite is close at hand ; but here again there is no 

 visible connexion. The marble of Ledbeg is usually a nearly pure 

 calcium carbonate. 



Now, if the marble is simply the dolomite altered (for any cal- 

 careous rock of the Assynt series except dolomite is out of the 

 question), it is very remarkable that the two rocks should be often 

 seen in proximity, and yet that there should be no evidence of a 

 passage between them. Great masses of igneous rock, culminating 

 in Cnoc-na-Strone, lie close at hand ; and smaller intrusions are here 

 and there visible in contact with the marble ; but patches of dolomite 

 within a few yards remain unaltered. Such facts are to me incon- 

 ceivable on the supposition that the marble and the dolomite are of 

 the same age. <=> 



We must next consider the relations between the Loch Ailsh 

 limestones and the rocks which bound their western margin. If the 

 limestones belong to the Assynt series, an unbroken succession must 

 be proved between them and the beds below. 



Working toward the south-east from Altnagalagach, we come, at 

 about 2| miles from the inn, to quartzite dipping at a low angle to 

 E.S.E. Fifty yards further on is dark-green gneiss with the same dip, 

 overlain in conformable succession by siliceous flaggy beds, quartzite, 

 dolomitic limestone of the Loch Ailsh type, and quartzite. This 

 section is on the strike of the Loch Ailsh limestone, and it displays 

 thin-bedded gneiss beloiv dolomite, confirming the view that the 

 limestone is in the Eastern Gneiss. 



We next run a section parallel to the last at about half a mile to 

 the north-east. Starting from Loch a' Mheallian, we leave behind us 

 the great igneous mass to the north of Loch Borrolan ; and descending 

 the slope to the south-east, we reach a small exposure of granitoid 

 Hebridean gneiss (No. 79, p. 416), without distinct foliation. Then 

 we come abruptly upon the marble and dolomite, which are continued 

 with a steady south-easterly dip as far as the road to Loch Ailsh, and 

 just beyond, in the slopes of Cnoc Chaorinie, are interstratified with 

 Caledonian. 



On the west bank of the Oykel, south of Kinloch Ailsh, the 

 Quartzite* of the Assynt series, which slopes down from Scounan, is 

 seen with its normal south-easterly dip ; and on the opposite bank 

 there are a few feet of the Brown Elags (Nos. 103, 104, p. 418) over- 

 lain by quartzite. The Loch Ailsh limestone appears in force a short 

 distance to the south-east. Further north, the igneous rock soon 

 cuts out the quartzite, and then the limestone itself. 



