IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 379 



Page 

 VI. Metamorpiiism resulting from the Post-Lower-Silurian Movements. 



1. Metamorphism of Arcbsean rocks 429 



2. „ of Cambrian strata 431 



8. „ of Silurian series 433 



4^ ^^ of the igneous rocks intrusive in the Cambrian and 



Silurian strata 434 



5. Succession of strata above the Moine Thrust-plane 435 



6. Denudation of the land surface before the time of the Old Eed 



Sandstone 438 



Index to Sections. 



1. Gneiss. \ . , 3. Basal quartzite. "l 

 1'. Basic dykes. J ^^^^«^^^- 3'. Igneous rocks in | 



2. Cambrian strata. basal quartzite. 

 2'. Igneous rocks intrusive in Cam- 4, Pipe-rock. | 



brian and Silurian formations. 4'. Igneous rocks in )- Silurian. 



" pipe-rock." 



5. Fucoid beds. 



6. Serpulite-grit. 



7. Limestone. J 



8. 1 Sheared gneiss 10. Eastern schists above Moine 



9. J (" Green Schist"). Thrust. 



Black lines = Thrusts. 1 1 1, Minor Thrusts. T T, Major and maximum Thrusts, 

 T\ Glencoul Thrust. T^, Ben-More Thrust. T^, Moine Thrust. 



Inteodtjction. 



In iN'ovember 1884 a brief notice or report was published of the 

 results of the work of the Geological Survey in Sutherland*. The 

 object of that report was mainly to announce that the detailed 

 mapping of the region had convinced us that the views entertained 

 by our former chief, Sir Eoderick Murchison, were no longer 

 tenable. It was then intended that an official Eeport should soon 

 be published, embodying the details of the survey work and con- 

 taining a full digest of all that had previously been done by other 

 observers. But the complicated structure of the region and the 

 necessity of continuing the mapping southward along the great 

 line of disturbance have hitherto delayed the publication of this 

 Eeport. It is felt, however, that instead of further postponement 

 until the conditions of official puiblication are fulfilled, it will be of 

 advantage to publish a 7'esume of the chief results which the Survey 

 has up to the present time obtained, and hence the present com- 

 munication is laid before the Society. 



Previous Liteeature. 



In fulfilment of the promise made in the preliminary notice 

 above referred to, we now offer an outline of the work of previous 

 observers, chiefly with the view of showing how far our own 

 labours have been forestalled by theirs. 



In 1819 MaccuUoch described a remarkable development of red 

 sandstone, quartz-rocks, and limestones among the gneiss and 

 schists of the North-west Highlands and Islands. He maintained 

 * ' Nature,' vol. xxxi. p. 29, Nov. 1884. 



