January 23, 190SJ 



NA TURE 



= /3 



pretation of the evidence had not the fascinating 

 simplicity of the other theory, and it was not whohy 

 riglit. The eastern and western gneisses are not 

 simply repetitions of the same series, and Murchison 

 was apparently right in his view that the upper 

 gneisses and schists are an independent and younger 

 series than the Lcwisian gneisses, which underlie the 

 Cambrian band to the west. Moreover, Nicol failed 

 to realise that the apparent bedding planes in the 

 eastern gneisses were not original, but secondary 

 structures due to earth movements. 



Murchison, with a theory attractive by its charm- 

 ing simplicity and far-reaching results, and right in 

 his recognition of the essential differences between the 

 eastern and western gneisses, swept his critic from 

 the field. Nicol, disheartened by the fate of views 



Nicol's researches " (p. 23), was not enough, al- 

 though it was supported by the work of Callaway 

 and Hudleston. In 1SS2-3 Prof. Lapworth mapped 

 in detail the classic sections on the shores of Loch 

 Eriboll ; he proved that the apparent sequence was 

 deceptive, and that the eastern gneisses were older 

 than the fossiliferous rocks, and had been placed 

 above them by earth movements; and it was his 

 crowning glory to recognise that many of the fine- 

 grained, shale-like rocks, which look like compara- 

 tively unaltered sediments, are the most intensely 

 altered rocks of the area; they consist, like ordinary 

 shales, of fragments of primary rocks, but instead of 

 having been formed by the usual agents of denudation 

 and deposition, they are due to crushing along planes 

 of earth movement. 



Unconformability of Cambrian quartzites on Tcrrido 



sandstone. Loih Coire Mhic FleaicbaV, 

 of the Controller of H.iM. Stationery Ofiic 



Rf produced with the aLthoriiy 



which he knew to be essentially correct, practically 

 gave up geological research, and went to his grave, 

 his geology despised and his conclusions rejected — by 

 all except his wife. In 1878, the year before Nicol's 

 death, the controversy was re-opened by that geo- 

 logical knight-errant. Dr. Hicks, who ran a tilt against 

 the Murchisonian theory. It survived his onslaught, 

 but two years later it received an almost fatal blow 

 from Prof. Bonney, who, by work near Loch Maree, 

 demonstrated that some of the rocks of the eastern 

 series were the old Lewisian gneiss brought up by 

 faults. The establishment of tfiis fact, which is de- 

 scribed in the memoir as " the first important advance 

 towards the solution of the problem of the succession 

 in the north-west Highlands since the publication of 



NO. 1995, ■^'OL. 77] 



The close of the controversy was now near at hand. 

 In 1883 Sir Archibald Geikie arranged for the detailed 

 mapping of the Loch Eriboll district by the Geological 

 Survey. The work was soon found to be far more 

 comple.K than had been e.xpected ; it was attacked with 

 invincible patience and thoroughness by the surveyors 

 under Peach and Home; the essential conclusions of 

 Nicol and Lapworth were confirmed, and it was 

 promptly announced in Nature that the Murchisonian 

 theory must be abandoned. In 18S8 a preliminary 

 report on the .Survey's investigations was published 

 bv the Geological Society, but it has taken another 

 nineteen years to extend the survey along the whole 

 of the overthrust line, and to prepare the materials 

 for publication. 



