﻿1861.] 



MTTRCHISOX AND GEIKIE HIGHLANDS. 



201 



hills. The same dip continues hy Kyle Rhea along the south-eastern 

 shore of the island, which is traversed by numerous N.W. and S.E. 

 dykes of greenstone. The same reddish tint is here observable that 

 was noticed in the description of the Balmacarra flagstones. The 

 cause is the same in this case also ; the red colour is a mere crust 

 owing to the oxidation of some of the component minerals ; while the 

 rock, when broken, is grey or white within. 



At Isle Oronsay, as at Balmacarra, we found a gradation from these 

 flagstones into the upper gneissose or schistose series. These schists 

 have a south-easterly dip, but are much crumpled in places. Near 



Pig. 16. — Section in Sleat, from near Ord to Knock. 



Knock. 



b f d 



b. Cambrian sandstone, d. Gneissose and schistose rocks, f. Fault. 



Knock a good section is obtained from the shore inland, showing the 

 curving of these strata, and about halfway between Knock and Ord 

 they are seen to graduate as usual into a lower series of quartzose 

 flaggy beds. 



2. Structure of the country between ilie Atlantic and the line of the 

 Great Glen. — Having traced the southward prolongation of the 

 quartz-rocks and limestones in Skye, until they are lost beneath the 

 waters of the Atlantic, we now give the results of several traverses 

 of the region to the east of these rocks, in order to show the cha- 

 racter of the upper gneissose series of deposits and the geological 

 structure of this part of Scotland. In former memoirs upon the 

 rocks of Sutherland, reference was made to the great apparent thick- 

 ness of the flaggy schistose strata which there overlie the upper lime- 

 stone and form the central and eastern portions of that county. The 

 thickness was indeed so great as to compel the belief that many 

 folds must necessarily exist, even although in most of the observable 

 sections the rocks continued to plunge towards the south-east. But 

 the data were wanting on which to speculate as to the character and 

 amount of such folds. This summer, however, we were fortunate 

 enough to obtain some illustrative sections which showed how de- 

 ceptive this steady south-easterly dip might really be, and how pro- 

 bable it was that, even where no change in the direction of inclina- 

 tion could be traced, the strata might nevertheless be repeated upon 

 themselves again and again. ~ 



Loch Broom to Oontin. — One of us continued the section from Loch 

 Broom across the wild uplands of the Dirry More to the Old Bed 

 Sandstone of the east coast, where it ascends the River Conon to 

 Contra. The amount of alluvium along the valleys rendered the 

 greater part of this traverse unsatisfactory ; but enough was ob- 

 served to justify the belief that when this region is properly mapped 

 it will be found to contain many anticlinal and synclinal folds as 

 well as local contortions of the strata. The flaggy and gneissose 



