J. W. Judd — On Volcanos, 7 



of considerable but varying elevation, the bold spurs of the Bakony 

 Wald coming down to its northern shores ; while the alluvial flats of 

 great extent on its banks, and the beaches at some elevation above 

 its surface, testify to the former considerably greater extent of the 

 lake. 



Let us now inquire what evidence is afforded to the geologist, 

 who studies its features, concerning the mode of origin of the 

 great depression in the earth's surface in which Lake Balaton lies. 



With respect to that agency which is so confidently appealed to 

 by several Scotch geologists as having originated the greater portion 

 of the rock-basins, in which lakes lie, — namely, the alleged power of 

 a glacier to excavate a depression in the earth's surface, — it will OTilj 

 be necessary to mention certain facts concerning the position and 

 features of Lake Balaton, to demonstrate the utter futility, at all 

 events in this case, of any such mode of explanation. Not only does 

 the district exhibit none of the usual evidences of powerful ice- 

 erosion, but it is quite impossible to conceive how such action could 

 have taken place here. The hills of the Bakony Wald, lying on the 

 north of the lake, are certainly not of sufficient extent and elevation 

 to have constituted the gathering ground of a great glacier, and the 

 only possible source of such an agent must therefore be sought in 

 the more distant Alps. Assuming for one moment that there existed 

 during the Glacial Period an ice-river of sufficient dimensions to have 

 extended from the Eastern Alps to Lake Balaton (though of this no 

 proof has, so far as I am aware, been ever adduced) — such a glacier 

 would naturally have followed the valley of the Mur or that of the 

 Eaab, in neither of which do great lakes exist, and could not have 

 originated Lake Balaton, which lies on the plateau separating the 

 basins of these two rivers. For an Alpine glacier to have exca- 

 vated the bed of Lake Balaton, it must have been able with a very 

 slight initial descent — the Eastern spurs of the Alps having a com- 

 paratively small elevation — to traverse a nearly level plain 100 

 miles in width, to have then surmounted a group of hills some 30 

 miles broad and from 1000 to 1200 feet in elevation, and after all 

 this expenditure of force to have retained sufficient energy to dig in 

 the midst of solid rocks a basin of vast extent. In short. Lake 

 Balaton lies exactly in that position which is of all others the least 

 favourable that it is possible to conceive for the action of the sup- 

 posed excavating power of a glacier from the Eastern Alps ; while 

 the points at which the erosive action of such a glacier would natur- 

 ally operate with greatest effect exhibit no traces whatever of the 

 formation of rock-basins. 



But in the case of Lake Balaton there is opportunely furnished to 

 the geologist a means of applying to the theory of ice-erosion a crucial 

 test. 



Eight in tlie midst of the lake, and almost dividing it into two 

 portions, rises the peninsula (once an island) of Tilianj^ ; this is a 

 mass of considerable elevation, composed for the most part of loose 

 basaltic tuffs, and evidently constituting the relics of an old volcanic 

 cone. 



