[2] Schmidt, Ec.  Geol.  Helvetiae, vol. ix., No. 4.

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and leaving the underlying gneisses rising through the remains of Permian, Triassic, and Jurassic sediments; while to the north the great limestone mountains and further north still, the Prealpes, carved from the remains of the recumbent folds, now stand with almost as little resemblance to the vanished mountains as the memories of the past have to its former intense reality.

These views as to the origin of the Alps, which are shared at the present day by so many distinguished geologists, had their origin in the labours of many now gone; dating back to Studer; finding their inspiration in the work of Heim, Suess, and Marcel Bertrand; and their consummation in that of Lugeon, Schardt, Rothpletz, Schmidt, and many others.  Nor must it be forgotten that nearer home, somewhat similar phenomena, necessarily on a smaller scale, were recognised by Lapworth, twenty-six years ago, in his work on the structure of the Scottish Highlands.

An important tectonic principle underlies the development of the phenomena we have just been reviewing.  The uppermost of the superimposed recumbent folds is more extended in its development than those which lie beneath.  Passing downwards from the highest of the folds, they are found to be less and less extended both in the northerly and in the southerly direction, speaking of the special case—­the Alps—­now before us.  This feature might be described somewhat differently.  We might say that those folds which had their roots farther

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to the south were the most drawn-out towards the north:  or again we might say that the synclinal or deep-seated part of the fold has lagged behind the anticlinal or what was originally the highest part of the fold, in the advance of the latter to the north.  The anticline has advanced relatively to the syncline.  To this law one exception only is observed in the Swiss Alps; the sheet of the Breche (Byecciendecke) falls short, in its northerly extension, of the underlying fold, which extends to form the Prealpes.

Contemplating such a generalised section as Professor Schmidt’s, or, indeed, more particular sections, such as those in the Mont Blanc Massif by Marcel Bertrand,[1] of the Dent de Morcles, Diablerets, Wildhorn, and Massif de la Breche by Lugeon,[2] or finally Termier’s section of the Pelvoux Massif,[3] one is reminded of the breaking of waves on a sloping beach.  The wave, retarded at its base, is carried forward above by its momentum, and finally spreads far up on the strand; and if it could there remain, the succeeding wave must necessarily find itself superimposed upon the first.  But no effects of inertia, no kinetic effects, may be called to our aid in explaining the formation of mountains.  Some geologists have accordingly supposed that in order to account for

[1] Marcel Bertrand, Cong.  Geol.  Internat., 1900, Guide Geol., xiii. a, p. 41.