A. Geikie—Crystalline Rocks of the Scottish Highlands. 11 
been such a fruitful subject of discussion. It was 
injunction to the officers now intrusted with the detailed survey 
of the region to divest themselves of any prepossessions in 
favor of published views and to map the actual facts in entire 
disregard of theory. ‘By the close of this last season the struc- 
ture of the Hriboll area had likewise been traced upon the six- 
inch maps, and I then went north to inspect the work. From 
time to time during the summer, reports had been made to me 
of the progress of the survey, but, though from the published 
descriptions of the tract, I was aware that its structure must be 
singularly complicated, and although apprised of the conclu- 
sions to which the surveyors, step by step, and almost against 
their will, had been driven, I was hardly prepared for the 
extraordinary geological structure which the ground itself pre- 
sented, or for the great change necessitated in the interpretation 
of the sections as given by Murchison. 
No one cursorily visiting the ground could form any notion 
of its extraordinary complication, which could only be satisfac- 
torily unravelled by patient detailed mapping such as had never 
yet been bestowed upon it. With every desire to follow the 
interpretation of my late chief, I criticised minutely each detail 
of the work upon the ground; but I found the evidence alto- 
gether overwhelming against the upward succession which 
Murchison believed to exist in Eriboll from the base of the 
Silurian strata into an upper conformable series of schists and 
gneisses. The nature of this evidence will be best understood 
from the subjoined report, which, at my request, Messrs. Peach 
and Horne have prepared. As the question of the succession 
of the rocks in the Northwest Highlands is still under discussion, 
I think it right to take the earliest opportunity of making this 
public declaration. It would require more space than can be 
fore, no further allusion is made at present. : 
he most remarkable features in the Eriboll area are the 
prodigious terrestrial displacements, to which there is certainly 
no parallel in Britain. Beginning with gentle foldings of the 
S, We trace these becoming increasingly steeper on their 
