1859.] murcmson — north highlands. 239 



that, with the exception of rare and insulated cases, as in the slate- 

 quarries of Easdale, Ballyhulish, <fcc, on the west coast, there is 

 scarcely a trace of true slaty cleavage throughout the vast masses of 

 the crystalline stratified rocks of the Highlands. Deeply lamenting 

 that my able and zealous friend the late Mr. D. Sharpe should, after 

 a hasty survey, have been led to express tho broad views on cleavage 

 which are printed in the ' Philosophical Transactions*,' I was for some 

 time im willing to advert to a subject on which I held opinions so very 

 much opposed to his own ; but now that I find Prof. Ramsay, who 

 is so well acquainted with the slaty rocks of North Wales, completely 

 agreeing with the views which Prof. Sedgwick and myself long ago 

 expressed, I can no longer forbear from pointing out what I am 

 compelled to consider an error. In fact, there can be no sort of 

 doubt that the different stratified masses of the Highlands have 

 resulted from successive depositions of mineral matter, which, though 

 subsequently much metamorphosed and also traversod by numerous 

 joints, have in the rarest cases only assumed a time slaty cleavage. 



Conclusion. — I may now rovert to the main object of this memoir, 

 the establishment of a clear order of succession among the oldest rocks 

 of the North-western Highlands. And here I have the satisfaction to 

 reiterate that not only Prof. Ramsay, who accompanied me, but 

 akso Prof. Harkness, who has since visited the north-western region 

 to satisfy doubts in his own mind, have both come to the conclusion 

 that my general views (as laid down in the map, PI. XII. vol. xv.) are 

 correct. 



On a point of such great stratigraphical importance, I cannot avoid 

 quoting the very words of Prof. Harkness, who, after visiting the 

 west of Sutherland, wrote to me thus : — " The gneiss which occupies 

 the western portion of Sutherland is of a character so unlike that 

 which forms the more eastern mountains of this country, that litho- 

 logical characters alone would almost justify the conclusion that 

 it appertains to a difforent geological epoch. Its strike is, as you 

 have shown, at variance with that of the newer gneiss where this 

 latter is in contact with the quartz-rocks and limestones forming the 

 Lower Silurians. 



" At many localities where the surface allows of the relation of 

 the upper gneiss and its immediately underlying deposits to be seen. 

 there is undoubted evidence of B perfect sequence ami conformity of 

 the strata which appertain to the apper quartz-rook and limestone 

 and the overlying flaggy gneiss : and this latter, in some districts 

 remote from the quartzites and lime-tones, presents the same uniform 

 dip with the rocks on which it reposes, as seen in Ben Hope and the 

 extensive oounl rj to the 8.E. 



" All the circumstances in connexion with this flaglike gneiss provi 

 it to be B member, superior in position, but intimately allied, of the 

 Lower Silurian- of the N.W. of Scotland. The mode in which the 



felspar-rook is found in relation to this gneiss at ESriboll indicates 

 thai no great line of dislocation separates the npper quartzites and 



■ Vol. axlii p, (4fi 

 VOL. X\I. — PAW I. I 



