﻿1861.] 



MCBCHISOX — HIGHLANDS. 



229 



is not to be seen between Eriboll House and the summit of the ridge. 

 The section is compiled from some disturbed beds which he observed 

 in a ravine at a certain distance on the strike of the formations, and 

 he thus introduces, beneath the real and visible section, in which all 

 the strata of the escarpment of the ridge are seen to dip to the E.S.E., 

 an ideal subterranean complication. In doing this he commingles 

 the existence of a great fault with a stupendous underground twist 

 of the fundamental gneiss, which rock is not seen nearer to this spot 

 than five or six miles, and which at that distance has a strike en- 

 tirely discordant to the quartz-rocks there lying upon it. Yet this 

 deep-seated granitic and hornblendic gneiss has, it is suggested, not 

 only changed its direction, and been thrown up conformably on the 

 quartz-rock and limestone with a south-easterly dip, but has also 

 been transformed into a micaceous and chloritic schist, wholly 

 unlike any portion of the old gneiss ! 



My conviction therefore remains unaltered, that, excepting local 

 and partial disturbances, and the irregular intrusion of igneous rocks, 

 the order above Eriboll House is absolutely that which has been 

 published by myself and witnessed by my associates*. It demon- 

 strates, in short, a true ascending order and transition from quartz- 

 rocks and limestone below, into superior micaceous and chloritic 

 schists (upper gneiss), as first indeed observed thirty-three years ago 

 by Professor Sedgwick and myself at this very spot. 



Secondly, Professor jSTicol has brought forward sections across 

 the strata at points where they are much broken and affected by 

 local intrusion of igneous rocks (notably figs. 3, 4, and 6, pp. 88, 

 89, 93), in order to show that the intrusive rocks occupy such a place 

 as to indicate a line of great dislocation along which the older gneiss 

 has been heaved up to the surface. But this view has been shown, 

 in former memoirs as well as in the present communication, to be 

 unfounded, inasmuch as similar igneous rocks (felspar-rocks, por- 

 phyries, and syenites) re-occur at various horizons in the series of 

 crystalline rocks, and do not invalidate the general ascending order, 

 or change the general conformity of the strata. 



Thirdly, at Assynt (see fig. 8, p. 96), the ascending section 

 from the Loch, as given by Professor Nicol, is made to terminate 

 with a limestone above the quartz-rocks ; it being held by him that 

 there is no quartz-rock above the limestone, except such as is brought 

 into that position from beneatli by upcast-faults. Now, in my own 

 section of the same localityt, an upper quartz-rock is shown to lie 

 conformably upon, and to succeed regularly to, the limestone ; and 

 in confirmation of the accuracy of this fact, and of the clear proofs 

 of a passage upwards from that limestone into a superior quartz-rock, 

 I have not only the testimony of Professors Ramsay and Harkness, 

 as previously cited, but that of Mr. Geikie, who, unaccompanied by 

 me, visited the same spot last summer, and saw unmistakeably clear 



* In fact, if Prof. Nicol's section be viewed as respects the portion of the strata 

 which can alone be seen, it is almost identical with my own. (See Prof. Hark- 

 ness's section, Quart. Journ. Geol. Soc. Aug. 1859, to 1 , xvi. p. 231, fig. 9.) 



t Quart. Journ. Geol. Soc. Aug. 1859, vol, xvi. p. 217, fig. 3. 

 VOL. XVII. — PART I. E 



