igoS.] 



THE PHYSICS OF THE EARTH. 233 



mergut, and of Upper Austria, to which corresponds on the south side the 

 Monti Lessini, near Verona, the mountains of Recoaro, those of the Sette 

 Comuni, and the considerable masses crowned by the summits of the Grappa, 

 the Col. Vicentino, the Monte Cavallo, the Monte Alatajur, and Monte 

 Nanos. Where, as in the case above mentioned, the secondary ranges of 

 the Alps rise to a greater altitude, and are completely separated from the 

 neighbouring portions of the central chain, it is impossible not to distinguish 

 them as distinct groups ; but the outermost ranges, which rarely rise above 

 the forest zone, are in all cases regarded as appendages of the adjoining 

 groups. These outer ranges are called in German Voralpen, and in Italian 

 Prealpi." (Ency. Brit., p. 623.) 



Again on page 620, this author remarks : 



" In every mountain system geographers are disposed to regard the 

 watershed, or boundary dividing the waters flowing towards the opposite 

 sides of the range, as marking the main chain ; and this usage is often 

 justified by the fact that the highest peaks lie on, or very near, the boundary 

 so defined. In applying this term in the case of the Alps, there are, however, 

 difficulties arising from their great extent and the number of their branches 

 and ramifications. Many of the loftiest groups lie altogether on one side of 

 that which we call the main chain, and at the eastern extremity, where all 

 drainage is ultimately borne to the Black Sea, we must be partly guided by 

 geological considerations in deciding which of several ranges deserves to 

 be considered pre-eminent." (Vol. I., p. 620.) 



Sir Archibald Geikie's discussion of the origin of the Alps, in 

 the article " Geology," Encyclopedia Britannica (pp. 2)72>'Z7A-)f bears 

 on the problem now before us: 



" The Alps, on the contrary, present an instructive example of the kind 

 of scenery that arises where a mass of high ground has resulted from the 

 intense corrugation and upheaval of a complicated series of stratified and 

 crystalline rocks, subsequently for a vast period carved by rain, frost, springs 

 and glaciers. We see how, on the outer flanks of those mountains among 

 the ridges of the Jura, the strata begin to undulate in long wave-like ridges, 

 and how, as we enter the main chain, the undulations assume a more gigantic 

 tumultuous character, until, along the central heights, the mountains lift 

 themselves towards the sky like the storm-swept crests of vast earth billows. 

 The whole aspect of the ground suggests intense commotion. Where the 

 strata appear along the clifi^s or slopes they may often be seen twisted and 

 crumpled on the most gigantic scale. Out of this complicated mass of 

 material the sub-aerial forces have been ceaselessly at work since its first 

 elevation. They have cut valleys, sometimes along the original depressions, 

 sometimes down the slopes. They have eroded lake-basins, dug out corries 

 or cirques, notched and furrowed the ridges, splintered the crests, and have 

 left no part of the original surface unmodified. But they have not effaced 

 all traces of the convulsions by which the Alps were upheaved." 



