1862.] EAMSAY GLACIAL OEIGIN OF LAKES. 189 



and others ? To answer this with precision, it wiU be necessary, first, 

 to examine several other hypotheses that by some may be thought 

 sufficient to account for them. 



It is well known that after the close of the Miocene epoch the 

 rocks of the Alps were much disturbed, — a circumstance proved by 

 the contortion of the Miocene strata, as for instance in the neigh- 

 bourhood of Lucerne, where, on the E-igi (and in other conglomeratic 

 mountains on the same strike), the strata are considered by the best 

 Swiss geologists to be repeatedly folded and fairly inverted, so that 

 the basement-beds form the top of the mountain instead of its 

 bottom, thus, by reversal of dip, plunging under the Eocene and Cre- 

 taceous strata of the mountains further south. The whole, as shown 

 by the rapid truncated foldings and the escarpments of the hills, has 

 since been much denuded, the denudation being of a kind and amount 

 that, to effect it, proves the lapse of a long period of time. Wit- 

 ness the outliers of Miocene strata in the upland valleys of the Jura. 

 Among these disturbed and denuded strata of Miocene and of older 

 dates, the Lakes of Geneva, Thun, Brienz, Lucerne, Zurich, Constance, 

 the "Wallen See, and the great lakes of North Italy lie. A knowledge 

 of the stratigraphical structure of the Alps, in my opinion, proves 

 that these lakes do not he among the strata in basins merely pro- 

 duced by disturbance of the rocks, but in hollows due to denuding 

 agencies that operated long after the comphcated foldings of the 

 Miocene and other strata were produced. 



First, none of these lakes lie in simple synclinal troughs. It is 

 the rarest thing in nature to find an anticlinal or a synclinal curve 

 from which some of the upper strata have not been removed by 

 denudation. I never yet saw a synclinal curve of which it can be 

 proved that the uppermost stratum in the basin is the highest layer 

 of the formation that was originally deposited over the area before 

 the curving and denudation of the country took place. The only 

 approach to this may possibly be in the upper valleys of the Jura, 

 where a part of the Miocene beds lie in basins separated by second- 

 ary anticlinally curved strata, the tops of the anticlinal bends having 

 been removed by denudation ; but these cases are surrounded with 

 difficulties. The lake-hollows in the Alps are, however, encircled by 

 rocks, the strikes, dips, and contortions of which often exhibit denu- 

 dation on an immense scale ; and in no case is it possible to affirm, 

 here we have a synclinal hoUow of which the original uppermost 

 beds remain. If these beds have disappeared to a great extent, then 

 it is evident that denudation has followed disturbance. The frag- 

 mentary state of the uppermost Miocene strata of the lowlands of 

 Switzerland proves this denudation. Again, if it be argued that in 

 the lake-areas these denudations have been produced by the waters of 

 the lakes, it is replied that, though waves may form cliifs, neither 

 running nor still water can scoop out deep trough-shaped hollows. 



Secondly, the same kind of argument applies to areas of mere 

 watery erosion by rivers. Eunning water may scoop out a sloping 

 valley or gorge, but (excepting little swallow-holes) it cannot form 

 and deepen a profound hollow, so as to leave a rocky barrier all 



