90 PROCEEDINGS OF 1HE GEOLOGICAL SOCIETY. [May 1 894,. 



illustration of the physical relations of the strata cannot fail to call 

 to our minds some of the efforts of previous authors, who, without 

 the key, were vainly endeavouring to explain on ordinary strati- 

 graphical principles the remarkable phenomena along the line of 

 chief disturbance. It is claimed for Prof. Lapworth, and perhaps 

 not unjustly, that he, working with tools forged by himself, has 

 given the key to the geology of two great provinces of Scotland. 1 

 At least in this district we may allow that he materially assisted in 

 opening the eyes of the officers of the Survey and others to the possi- 

 bilities of the case, and that the former have not been slow to profit 

 by his teaching. Nine years have now elapsed since the close of the 

 Highland Controversy, and the interval has been one of steady pro- 

 gress in recognizing the true, but nevertheless extraordinary, struc- 

 ture of the country. Well indeed might Prof. Lapworth comment 

 on the descriptive character of this portion of Messrs. Peach and 

 Home's paper, whilst allowing that the general conclusions arrived 

 at were very similar to those which he had himself indicated. Such 

 sections are, to a certain extent, astounding, yet they do occur. 



The subject of Thrust-planes has been pretty well grasped by this 

 time, and some people have been looking for them where probably 

 they do not exist. The three chief thrust-planes of this region in 

 order from west to east are — (1) the Glencoul Thrust; (2) the 

 Ben More Thrust ; (3) the Moine Thrust. A series of horizontal 

 sections drawn across the general strike of the district exhibits the 

 effects of one or more of these in combination with the results of 

 minor thrusts. Nothing but the most intimate acquaintance with 

 each particular rock could ever have enabled the authors to put 

 together the pieces of such an extraordinary jumble, though when 

 once the idea is grasped there seems to be a certain amount of 

 system in the displacements. One of the more northern sections,, 

 about five miles in length, exhibits the wonderful manner in which 

 a swirl of the Cambrian beds, from quartzite to dolomite all told, is 

 caught up, as a kind of iulay, into the flanks of the Archsean gneiss. 

 It was the re-appearance of this Archaean gneiss, far to the eastward 

 of its accepted position, which so puzzled the older geologists, often 

 figuring as the ' igneous rock' of Murchison or the ' Logan rock' of 

 Heddle. Such, within certain limits, is the structure of Coniveall, 

 the southern peak of Ben More of Assynt. This structure, at the 

 Stack of Glencoul, is further complicated by an outlier of the eastern 

 or Moine Schists, brought forward several miles to the westward of 



1 Bertrand, op. cit. p. 121. 



