J. W. Judd — On Volcanos, 11 



character and equal in extent occur in otlier districts^ though in a 

 manner which renders their effects less capable of detection by us, — 

 are we not justified in accepting such movements as capable of 

 explaining the formation of lake-basins in all cases, rather than 

 in having recourse to a purely hypothetical cause ? 



And if this mode of viewing the subject be a legitimate one, what 

 reason can be adduced for doubting that those great disturbing 

 forces — which, during and subsequently to the Oligocene and 

 Miocene periods, have given rise to such startling results in the 

 contortion and even in the inversion of the rocks of the Alps, but 

 which at the same time have produced only inconsiderable effects in 

 the areas immediately surrounding them — must have originated, in 

 different parts of the great lines of drainage descending from those 

 mountains, such inequalities of movement as could not fail to result 

 in the formation of lake-basins ? Now it is a most striking and 

 significant circumstance that a careful study of the deposits that 

 were formed immediately around the Alpine System during the periods 

 of most violent movement leads, to the conclusion that, near the 

 limits of the disturbed and unaffected areas, lakes were constantly 

 being formed and filled up with sediments. Nor have we the 

 smallest grounds for inferring that such movements have altogether 

 ceased, and could have played no part in the origination of the 

 existing lakes in similar positions ; but, on the contrary, even the 

 stoutest advocates of the glacial origin of these lakes admit that con- 

 siderable movements must have taken place, both in the Alps and 

 elsewhere, during and subsequently to the Glacial Period. 



This is the view of the mode of origin of the great Alpine lakes 

 which was maintained by the late Sir Charles Lyell, and which has 

 been supported by the critical examination of a number of special 

 examples by the Eev. T. G. Bonney. And the same opinion con- 

 cerning the formation of these lakes is held by the distinguished 

 geologists of Germany, Switzerland, France and Italy, who during 

 the last thirty years have made such splendid additions to our know- 

 ledge of Alpine geology ; with but one solitary exception, we believe, 

 all the geologists who have especially devoted themselves to the study 

 of these regions have rejected the hypothesis of the glacier-erosion 

 of the lake-basins as both unnecessary and inadequate. 



Of the various facts which have been adduced as lending support to 

 the doctrine of the erosion of lake-basins by ice, the only one which can 

 be said to afford a presumption in its favour is the abundance of 

 lakes in districts which have been recently subjected to glacial 

 erosion. But this fact, as was shown by the late Sir Charles Tjyell, 

 is capable of another and very simple explanation, without calling 

 in the agency of so problematical a cause as the excavating power 

 of ice. A very large proportion of the lakes and lakelets, found in 

 glaciated districts, are in reality formed through the arrest of drain- 

 age by the peculiar and often seemingly capricious modes of accumu- 

 lation of moraine matter. The smaller number of true rock- basins 

 which remain, after eliminating the moraine lakes, appear indeed to 

 owe their existence also to the action of glaciers, but in a very dif- 



