Presidential Address to Geological Section. 457 



of Wales by Murchison.i The discovery of the Olenellus fauna, indicating 

 the lowest division of the Cambrian system, in the quartzite-limestone 

 series by the Geological Survey in 1891 ^ demonstrated the Pre-Cambrian 

 age of the Torridon Sandstone. In view of that discovery, which proves 

 the great antiquity of the Torridonian sediments, it is impossible to climb 

 those picturesque mountains in Assynt or Applecross without being 

 impressed with the unaltered character of these deposits. Yet it can be 

 shown that under the influence of Post-Cambrian movements they approach 

 the type of crystalline schists. 



Before proceeding to the consideration of the Durness series of quartzites 

 and limestones and their relations to the Eastern Schists, brief reference 

 must be made to the controversy between Murchisou and Nicol regarding 

 the sequence of the strata. 



The detailed mapping of the belt between Eriboll and Skye by the 

 Geological Survey has completely confirmed Nicol's conclusions (1) that 

 the limestone is the highest member of the Durness series ; (2) that the 

 so-called ' Upper Quartzite' and ' Upper Limestone' of Murchisou's sections 

 ai'e merely the repetition of the lower quartzite and limestone due to faults 

 or folds ; (3) that there is no conformable sequence from the quartzites 

 and limestones into the overlying schists and gneiss ; (4) that the line of 

 junction is a line of fault indicated by proofs of fracture and contortion of 

 the strata. It is true that in the course of his investigations Nicol's views 

 underwent a process of evolution, and that even in the form in which he 

 ultimately presented them he did not grasp the whole truth. AVe now 

 know that he was in error when he regarded portions of the Archajan 

 gneiss, occurring in the displaced masses, as igneous rocks intruded during 

 the earth-movements, and that he failed to realize the evidence bearing on 

 dynamic metamorphism resulting from these movements. But I do not 

 doubt that the verdict of the impartial historian will be that Nicol dis- 

 played the qualities of a great stratigraphist in grappling with the tectonics 

 of one of the most complicated mountain chains in Europe. 



The period now under review embraces the reopening of that controversy 

 in 1878 by Dr. Hicks, and its close in 1884 after the publication of the 

 "Eeport on the Geology of the North- West of Sutherland " by the Geo- 

 logical Survey.^ The Survey work has confirmed Professor Bonney's 

 identification of the Lewisian gneiss and Torridon Sandstone in Glen 

 Logan, Kinlochewe,* brought into that position by a reversed fault ; and 

 Dr. Callaway's conclusions regarding overthrust faulting at Loch Broom, 

 in Assynt and in Glencoul.^ Special reference must be made to the 

 remarkable series of papers by Professor Lapworth on "The Secret of the 

 Highlands," in which he demonstrated the accuracy of Nicol's main con- 

 clusions, and pointed out that the stratigraphical phenomena are but the 

 Qounterpart of those in the Alps as described by Heim.'^ His researches, 

 moreover, led him to a departure from Professor Nicol's views regarding 

 the age, composition, and mode of formation of the Eastern Schists, for in 

 the paper which he communicated to the Geologists' Association in 1884 

 he announced that their present foliated and mineralogical characters had 

 been developed by the crust-movements which operated in that region 

 since the time of the Durness quartzites and limestones.' Allusion must 



1 Ibid., vol. XV, p. 353. 

 ^ Ibid., vol. xlviii, p. 227. 

 3 Nature, vol. xxxi, p. 29, November, 1884. 

 * Quart. Jouru. Geol. See, vol. xxxvi, p. 93. 

 ^ Ibid., vol. xxxix, p. 416. 



8 Geol. Mag., Dec. II, Vol. X (1883), pp. 120, 193, 337. 

 ' Proc. Geol. Assoc, vol. viii, p. 438 ; Geol. Mag., Dec. Ill, Vol. II (1885), 

 p. 97. 



