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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Feb. 6, 



the north-western regions of Scotland probably extended south- 

 wards across the mountainous tracts to the south of the Caledonian 

 Canal. But this application of the classification of the rocks of the 

 north-west was based on general observations only of earlier years; 

 and a more exact survey was called for before it could be held as 

 proved that the great mass of the Scottish Highlands displayed the 

 same order of succession as had been demonstrated to exist in the 

 north-western tracts. 



It was also necessary to trace the development of the Sutherland- 

 shire series to the south-west, through Eoss-shire, so as to complete 

 the base-line from which the rest of the Highlands should be worked 

 out in detail. 



For this purpose we devoted two months of the last summer to an 

 examination of the Eoss-shire district and the region southwards to 

 the Highland border, including the islands of Lewis, Skye, Islay, and 

 Jura. The results of this survey, completely confirming our previous 

 views, are laid before the Society in the present memoir. 



I. Eange of the Laurentian or Older Gneiss in the Hebrides 

 and North-Western Highlands. 



Lewis and Harris. — As announced in previous memoirs, the 

 greatest spread of the Older or Laurentian Gneiss is seen in the Long 

 Island of the Hebrides, by much the larger portion of which is called 

 " the Lewis*," the lesser or southern part being " the Harris." 



In both these tracts the mineralogical character of this older 

 gneiss, and its numerous contortions, have been so well described by 

 Macculloch, that little remains to be said on those heads by others. 

 That author has, however, omitted to state that the usual and 

 dominant direction of the strata is transverse to the elongated form 

 of this island ; for, whilst the geographical axis of the whole, as seen 

 in any map, is from X.N.E. to S.S.W., the normal strike of the beds 

 of gneiss is from S.E. to X."W., or across the island. The traveller 

 who has not much time at his disposal may convince himself of this 

 fact in a few hours by examining the rocks which rise up to the 

 west of the Port of Stornoway. If he should have sailed from the 

 opposite mainland, and have there observed that on the shores of 

 Lochs Maree, Gairloeh, and Torridon the Laurentian gneiss has a 

 persistent strike from N.W. to S.E., with dips to the N.E. and S.W., 

 he will find precisely the same phenomena in the Lewis. 



"Whether he examines the various points of rock — so well exposed 

 in the pleasure-grounds of Stomoway Castle, and particularly those 

 which have been cut through by Sir James Matheson on the banks 

 of the torrential river Creed, or the sea-clifls of the headlands on 

 the east — or should cross the peat-covered moors, to the western 

 shores and the interior, to Morsgail or to Soval, or even should 

 extend his researches into the Harris beyond Athline, — he every- 

 where meets with the same phenomenon of a prevalent strike from 



* Pronounced " Lews." 



