Prof. OC. Lapworth—The Secret of the Highlands. 121 
where the rocks of this remarkable zone come out in force upon the 
shore-line, and where, as a consequence, the stratigraphist might 
expect a more than ordinary abundance of serviceable rock-exposures. 
And, finally, as the keener disputants in the Highland controversy 
have already published their views as to the physical structure of 
this area, I should have the advantage of working alone, and drawing 
my own unfettered conclusions. 
The final results of my investigations in the Durness-Hriboll 
region during August last seem to me to indicate most distinctly 
the probable truth of the theory which has long appeared to myself 
to be the only possible solution of the Highland difficulty. I believe 
that we have in the so-called metamorphic Silurian region of the 
Highlands of Seotland a portion of an old mountain system, formed 
of a complex of rock formations of very different geological ages. 
These have been crushed and crumpled together by excessive lateral 
pressure, locally inverted, profoundly dislocated, and partially meta- 
morphosed. This mountain range, or plexus of ranges, which must 
have been originally of the general type of those of the Alps or 
Alleghanies, is of such vast geological antiquity, that all its 
superior portions have long since been removed by denudation, so 
that, as a general rule, only its interior and most complicated 
portions are preserved by us. In the area partly worked out by - 
myself, the stratigraphical phenomena are identical in character 
with those developed by Rogers, Suess, Heim, and Brégger in extra- 
British mountain regions. They appear to me to account so naturally 
for the diverse views hitherto published by those who have person- 
ally studied the stratigraphy of the North-west Highlands, and to 
indicate so clearly the common ground of accord upon which all 
parties may eventually meet, that I am emboldened to give them in 
outline in this place, in anticipation of a more detailed paper upon the 
subject, which I hope to publish elsewhere. It is for those who 
are interested in this great geological problem to test for themselves 
the truth of these conclusions, by their consonance with their own’ 
discoveries, or to point out those difficulties which at present stand 
in the way of their provisional adoption. 
I.—Apparent structure of the Durness-Eriboll region. (See Fig. 1.’) 
At first sight it would appear that the rocks of the Durness- 
Hriboll region are easily grouped, and that they are arranged with 
remarkable geological simplicity. 
(A.) Lowest of all lies an enormous formation of massive gneisses 
with coarse folia of quartz, felspar, and hornblende (and more 
rarely mica). These gneisses are almost vertical, and have a steady 
N.W. and §.E. strike. They form the basal or fundamental gneiss 
of some authorities, the Hebridian, Lewisian, or Laurentian of others. 
(B.) Upon the eroded edges of the Hebridian gneiss rest uncon- 
formably the basal beds of a second formation, the strata of which 
have a very gentle inclination, and strike, as a whole, to the north- 
1 The illustrative Figures will appear in the second part of this paper. 
