TRANSACTIONS OF SECTION C. 1011 
strata in the Jura do to the intense crumplings of those of the Alps; and these in 
turn pass insensibly into the slightly undulating or horizontal strata of the southern 
half of this island. 
We may perhaps add another comparison between the existing mountain-chain 
of Southern Europe and the ‘ basal wreck’ of Northern Europe, one which I find 
has been already suggested by Professor Bonney. The Miocene Conglomerates, 
which in the Rigi and other flanking mountain masses of the Alpine chain are 
found piled to the depth of many thousands of feet, seem to be exactly represented 
in its prototype by the vast masses of the * Old-Red’ Conglomerate. 
Vast as were the three series of movements to which I have been referring, I 
believe that the Scandinavian and Highland rocks bear the impress of a still 
rvander series of disturbances than either of these—one at the same time of older 
date and far more universal in its effects. 
Many writers have treated of the great divisional planes, almost everywhere 
conspicuous in the Highland rock-masses, as being necessarily coincident with planes 
of sedimentation. It is manifest, indeed, that the tracing of sequences and uncon- 
formities among such rocks must proceed upon the assumption that the planes of 
foliation and stratification are coincident. Murchison and Geikie so fully recog- 
nised the fact that this proposition lay at the very root of their arguments con- 
cerning a Highland succession, that they added a supplement to their paper to 
illustrate and enforce it. 
It must not be forgotten, however, that the truth of this proposition has not 
only been doubted, but has been stoutly contested by many of the most profound 
thinkers on geological questions. 
As long ago as 1822, Professor Henslow, in a very remarkable paper, showed 
that the rocks of Anglesea are traversed by a system of divisional planes, which 
intersect the bedding at a very high angle, and must have been produced long sub- 
sequently to the latter; and in 1835 Professor Sedgwick extended the observations 
and enforced the arguments of Henslow. 
At an even earlier date, Poulett Scrope had shown, by his study of viscous Javas, 
that the planes along which crystalline action takes place are determined by 
pressure and strain; and he insisted that the foliation of metamorphic masses was 
a phenomenon strictly analogous to the banding of rhyolitic lavas. 
Charles Darwin, the pupil of Henslow and the friend of Poulett Scrope—whose 
Jabours in the geological field would perhaps have met with fuller recognition had 
they not been overshadowed by his still greater achievements in the world of 
biological thought—strongly maintained the truth of these views. He added the 
important observation that, in the South-American continent, the planes of foliation 
are seen everywhere, over enormous areas, to be parallel to those of cleavage ; and 
_that these latter are of secondary origin and due to lateral pressure, the observa- 
tions of Sharpe and the experiments of Sorby have convincingly demonstrated. 
That the schists and gneisses of our Highlands and of Scandinavia have resulted 
from crystallising forces, acting upon strata of sandstone, clay and limestone, or 
upon igneous materials constituting laya-currents, or intrusive sheets, dykes, and 
bosses, I see every reason for believing. That these re-crystallised and highly- 
foliated masses in the great majority of cases maintain their original positions and 
relations, or indeed anything approaching their original positions and relations, I 
greatly doubt; and my doubt on this point has increased the more I have studied 
the Highland rocks. 
Thin bands of quartzite may be the rolled-out representatives of massive beds 
of sandstone or conglomerate ; wide-spreading schists may consist of the crystallised 
materials of clays and shales, crumpled, pleated, and kneaded together in endless 
conyolutions; vast sheets of gneiss may have originally been intrusive bosses of 
granite or thick strata of arkose. How, then, are we to apply the ordinary principles 
that regulate questions concerning dip and strike, and unconformity in the case of 
sedimentary deposits, to highly-altered rocks like these ? 
The observations of Jukes, Allport, and Phillips on some of the simpler and more 
easily explicable examples of the production of foliation in rocks require to be 
cautiously extended, by patient study in the field and in the laboratory, to cases of 
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