CHAP. IX ANCIENT GLACIAL EPOCHS 179 



and forty-five feet thick ! The granite is red, and of a 

 peculiar kind which cannot be matched anywhere in the 

 Alps, or indeed elsewhere. Similar erratics have also been 

 found in beds of the same age in the Carpathians and in 

 the Apennines, indicating probably an extensive inland 

 European sea into which glaciers descended from the sur- 

 rounding mountains, depositing these erratics, and cooling 

 the water so as to destroy the mollusca and other organisms 

 which had previously inhabited it. It is to be observed 

 that wherever these erratics occur they are always in the 

 vicinity of great mountain ranges ; and although these 

 can be proved to have been in great part elevated during 

 the Tertiary period, we must also remember that they 

 must have been since very much lowered by denudation, of 

 the amount of which, the enormously thick Eocene and 

 Miocene beds now forming portions of them is in some 

 degree a measure as well as a proof. It is not therefore at 

 all improbable that during some part of the Tertiary j)eriod 

 these mountains may have been far higher than they 

 are now, and this we know might be sufficient for the pro- 

 duction of glaciers descending to the sea-level, even were 

 the climate of the lowlands somewhat warmer than at 

 present.^ 



The Weight of the Negative Evidence. — But when we 

 proceed to examine the Tertiary deposits of other parts of 



^ Prof. J. "\V. Jiidd says : "In the case of the Alps I know of no glacial 

 phenomena which are not capable of being explained, like those of New 

 Zealand, by a great extension of the area of the tracts above the snow-line 

 which would collect more ample supplies for the glaciers protruded into 

 surrounding plains. And when we survey the gi'and panoramas of ridges, 

 pinnacles, and peaks produced for the most part by sub-aerial action, we 

 may well be prepared to admit that before the intervening ravines and 

 valleys were excavated, the glaciers shed from the elevated plateaux must 

 have been of vastly greater magnitude than at present," (Contributions 

 to the Study of A-'olcanoes, Geological Magazine, 1876, p. 536.) Professor 

 Judd applies these remarks to the last as Avell as to previous glacial periods 

 in the Alps ; but surely there has been no such extensive alteration and 

 lowering of the surface of the country since the erratic blocks were de- 

 posited on the Jura and the great moraines formed in North Italy, as this 

 theory would imply. We can hardly suppose wide areas to have been 

 lowered thousands of feet by denudation, and yet have left other adjacent 

 areas apparently untouched ; and it is even very doubtful whether such 

 an extension of the snow-fields would alone suffice for the effects which were 

 certainly produced. 



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