998 REPORT—1885. 
‘ Upper Quartzite ’ and the ‘ Upper Limestone’ of that author were proved to have 
no real existence.} 
5. What so many authors had taken for a conformable upward succession of 
this older Palzozoic formation into overlying schist and gneiss, was asserted by 
Nicol to be an altogether fallacious appearance, due to the thrusting of the crystal- 
line rocks over the sedimentary ones by great overthrow-faults. 
6. The relations between these crystalline and sedimentary strata in the Scottish 
Highlands were shown to be precisely similar to those which are constantly pro- 
duced by lateral pressure in all great mountain-chains, and consist of sharp foldings, 
inversions, and faulting on the very grandest scale. Examples of overthrow-faults, 
similar to those of the Scottish Highlands, were instanced by Nicol as occurring in 
the Alps.? 
We cannot perhaps better illustrate the position maintained by Nicol in this 
remarkable paper than by quoting the following passage :—‘ Until some rational 
theory is produced of the mode in which an overlying formation, hundreds of square 
miles in extent and thousands of feet in thickness, can have been metamorphosed, 
whilst the underlying formation of equal thickness and scarcely less in extent has 
escaped, we shall be justified in admitting inversions and extrusion’ (7.¢., of older 
masses on younger, as he explains his meaning to be) ‘equal to those of the 
Alps.’$ 
The only serious error into which Nicol fell—and after all it is a very incon- 
siderable one judged in comparison with his undoubtedly great achievements—was 
that of attaching too much importance to the influence of igneous intrusions in 
connection with the tremendous inversions and overthrow-faults to which he so 
clearly showed that these Highland rocks have been subjected. We now know 
that many of these supposed intrusive masses, though really of igneous origin in all 
probability, were of older date than the Paleozoic rocks in the midst of which they 
le; and that they were brought into their present positions, not by intrusion in a 
liquid state, but by complicated faulting. It must be remembered that these 
‘ granulites,’ as Nicol very justly called them,‘ for they present a wonderful analogy 
with the typical rocks of Saxony which are known by that name, have long been 
regarded by geologists as among the most difficult and perplexing of rocks to ex- 
plain the origin of, though the recent researches of Dr. Lehmann haye now done 
something towards the solution of the problem. 
Calmly reviewing, in the light of our present knowledge, the grand work accom- 
plished single-handed by Nicol, I have no hesitation in asserting that when this 
Association met here twenty-six years ago, he had already mastered the great High- 
land problem in all its essential details, and that his results were distinctly pro- 
claimed during the meetings of this Section. 
If, then, Nicol had so fully solved this great problem of Highland geology 
twenty-six years ago, how is it, may not unreasonably be asked, that we have 
waited so long for the justice of these views to be admitted ? 
A variety of circumstances have contributed to bring about this unfortunate 
result. Murchison was at the time too old and infirm to examine in careful detail 
the wild districts where these rock-masses are exhibited. Hence Nicol’s oft-repeated 
invitations to view the sections in his company remained unheeded, and we find 
the great geologist of Aberdeen writing in 1866 his concluding plaintive words in 
this memorable discussion: ‘I must express my most sincere regret that my illus- 
trious opponent—from whom only the most thorough conviction that my views are 
well founded, and that the question was one on which it became a teacher of 
geology in Scotland to give no uncertain utterances, could haye compelled me to 
differ—has never found it convenient to meet me again in the North. Iam con- 
vinced that we agree in so many essential points, that a few hours together in the 
field would bring us nearer in opinion than whole yolumes of controversy.” 
The phalanx of eminent geological authorities opposed to the views of Nicol, 
Quart. Journ, Geol, Soc. vol. xvii. (1861), pp. 98, 108, 109, &c. 
Ibid. pp. 108, 109, 110. 8 Thid. p. 110. 
Ibid. p. 89. 5 Geology of the North of Scotland, p. 96. 
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