474 
NATURE 
° 4 
[ Sept. 17, 1885 
deeply by gigantic earth-throes, or sealed up under massive 
lava-streams. 
Down to post-glacial times Scotland, and what are now its 
outlying islands, remained united with Scandinavia. I need not 
remind you how, during the glacial period, they were the scene 
of a similar succession of events ; while from their then far more 
elevated mountain summits streams of glacier-ice flowed down 
and relieved the mantle of snow which enveloped them. 
But at a very recent geological period, and indeed since the 
adpearance of man in this part of our globe, the separation of 
the two areas, so long united, was brought about. In the district 
now constituting the North Sea, which separates the two countries, 
great faults, originating in the Tertiary epoch, appear to have let 
down wide tracts of the softer Secondary strata among the harder 
crystalline rock-masses. The numerous changes of level, of which 
we find such abundant evidence around the shores of this sea, 
facilitated the wearing away of the whole of these softer 
Secondary deposits, except the slight fringes that remain along 
the shores of Sutherland, Ross, and Cromarty, on the one hand, 
and the isolated patches forming Scania, Jutland, and the sur- 
rounding islands on the other. Little could the Vikings, as they 
sailed over this shallow sea, have imagined that their predecessors 
in these regions were able to roam on foot from Norroway to 
Suderey ! 
It is almost impossible to over-estimate the effects produced 
by the several denudations to which Scandinavia and the Scottish 
Highlands have been successively subjected. In that which 
occurred during the later Tertiary periods, almost every portion 
of the non-crystalline rocks that rose above the sea-level was 
either entirely removed or converted into level plains, which, 
covered with drift deposits, now form districts like Scania and 
Denmark. Where, as in the great central valley of Scotland, 
hard volcanic masses are associated with the softer sedimentary 
rocks, the former are left rising as picturesque crags, standing 
boldly up above the general level, while the latter are worn 
down and buried under drift. In the west of Scotland a chain 
of volcanic mountains, with summits towering to the height of 
from ten to fifteen thousand feet, have been reduced by this same 
denudation to basal-wrecks, the highest portions of which attain 
to but little more than 3,000 feet above the sea-level ! 
During the grea* elevation and denudation which marked the 
Neocomian period, thousands of feet of strata must have been 
removed over wide areas, as is proved by the wonderful overlap 
of the Cretaceous beds on all the older strata. 
Of the enormous sub-aérial waste which went on in these 
Northern Alps during the Newer Palzeozoic periods we have 
impressive evidence in the vast masses of the Old Red Sandstone 
and Carboniferous rocks—themselves only a series of fragments 
that have survived the later denudations—for these rocks are 
built up of the materials derived from our Northern Alps. 
The Torridon Sandstone is the monument, and a very striking 
monument too, of another and still earlier period of enormous 
denudation. The thousands of feet of conglomerate and sand- 
stone of which it is made up consist of the disintegrated crystals 
of granites and gneisses that have been swept away. 
When we penetrate towards the axis of this eroded mountain- 
chain, the proofs of the magnitude of these denudations become 
even more striking and impressive. Here we see, towering aloft, 
the ruined buttresses of vast roc’sy arches, that when complete 
must have risen miles above the present surface ; there we find, 
lying side by side, rock-masses that could only have been brought 
together by displacements of tens of thousands of feet; yet so 
complete has been the planing down of the surface since, that it 
requires the most careful study even to detect the almost obli- 
terated traces of these grand movements. The Alps and the 
Himalayas, durinz their elevation, have suffered enormous waste 
and denudation ; but if the elevation were to cease and the waste 
to go on till these magnificent mountain-chains were reduced to 
masses of diminutive peaks, ranging from 2,000 to 8,000 feet in 
height, we should then have the counterpart of this stupendous 
ruin of the mountain-chain of the north. 
The history of the series of successive movements to which 
the rock-masses of our Highlands have been subjected is one 
well worthy of the most attentive study. When the evidence 
bearing upon the subject is carefully sifted and weighed, we 
become convinced of the fact that many of these movements— 
including some on a prodigious scale—must have taken place 
during what we are commonly accustomed to regard as com- 
paratively recent geological periods. 
On the eastern coast of Sutherland, a mass of Secondary 
rocks, including several thousands of feet of Triassic, Rheetic, 
and Jurassic strata, has been let down by a gigantic fault, so as 
to be placed in juxtaposition with the Old Red Sandstone and 
the crystalline rocks. Now, taking the very lowest estimates of 
the thicknesses of the several strata affected, the vertical “‘throw’’ 
of this fault must have exceeded a mile! It may not improbably,. 
indeed, have been at least double or treble that amount! Yet 
this great dislocation was certainly produced at a later date than 
the Upper-Jurassic period, for rocks of that age are found to be 
affected by it. 
Along the coasts of the Black Isle, strata of Middle and 
Upper Jurassic age are similarly found faulted against the ‘* Old 
Red” and the crystalline rocks. 
On the other side of the North Sea, in Ando, one of the 
Lofoten Isles, a patch of Lower-Oolite strata, consisting of 
marine and estuarine strata, and including beds of coal like that 
of Brora, is found let down by gigantic faults into the very heart 
of the crystalline rocks of the district. In Scania, the whole of 
the Secondary rock-masses owe their preservation in the same 
way to a plexus of tremendous faults, by which they have been 
entangled among the harder rocks. ‘These faults have affected 
not only the Jurassic strata, but even the very youngest members 
of the Cretaceous series. 
Nor are we without evidence that some of the great faults are 
of post-Cretaceous age, in this country, for in the Western High- 
lands displacements of several thousands of feet have been detected, 
which affect not only the Upper Cretace us, but also the Older 
Tertiary rocks. 
The effects produced by these great dis’ ocations, which have 
a generally parallel direction in our Highlaids, from north-east 
to south-west, are of the most startling character. Great strips 
of Triassic and Old Red Sandstone strata, like those of Elgin, 
and Turriff, and Yomintoul, and of the line of the Caledonian 
Canal, are found let down among the crystalline rocks by these 
gigantic faults. 
The great central valley of Scotland itself consists of masses 
of Newer Paleozoic strata, faulted down between the harder 
Archean and Lower Palaeozoic rocks, which form the High- 
lands on the one hand, and the Borderland on the other. 
The evidences of the existence of these great faults were 
collected by many of the older Scottish geologists, like Lan- 
dale, Bald, Chalmers, Milne-Hoem, and Nicol; and the 
accurate mapping of the country by the officers of the 
Geological Survey has, on the whole, tended to confirm their 
results. With regard to the age of these great dislocations of 
Central Scotland, it can only be certazndy affirmed that they are 
of more recent date than the youngest Carboniferous strata ; but 
I have long believed that, like many similar dislocations both in 
our own Highlands and in Scandinavia, they are really post- 
Cretaceous. 
Less difficulty perhaps will be found in accepting this appa- 
rently startling conclusion, when we remember that a complicated 
series of fractures injected by the lavas of the Great Tertiary 
volcanic foci of the West, extend right across the Highlands, 
the central valley, and the Borderlands of Scotland, and even 
traverse the whole series of the Secondary rocks in the North of 
England. 
The indications of the tremenlous manifestations of subter- 
ranean energy, to which these great dislocations owe their 
origin, are sometimes of a very striking kind. For hundreds of 
yards on either side of the faults, the two sets of strata are found 
bent and crumpled, and not unfrequently crushed into the finest 
dust (‘‘fault-rock”’). In the case of the great Sutherland-fault, 
to which I have previously alluded, we have a beautiful illustra- 
tion of the way in which mineral veins may originate along such 
lines of fissure, for in the interstices of the granite of the Ord, 
where it has been broken up along this certainly post-Jurassic, 
and probably Tertiary fault, fluor-spar and pyrites have been 
deposited in large quantities. ‘ 
It is impossible to study the tremendous movements and dis- 
locations, and the enormous amount of denudation which have 
taken place in the Highlands and surrounding districts during 
Tertiary times, without being convinced that all the existing 
surface-features of the country must date from a comparatively 
recent period, The vast movements which have placed soft and 
hard masses in opposition along certain parallel lines—generally 
ranging in a north-east and south-west direction—and the denu- 
dation which has worn away the former, while it has left the 
latter standing in relief, must, I believe, both be referred to the 
Tertiary period ; though the disposition of rock-masses brought 
