THE GORGE OF THE AAR AND ITS TEACHINGS 143 



APPENDIX 



An American critic of this article, in Science (N. S., 

 vol. iv., No. 95), declares that my " derogatory references 

 to the explanation of lakes by subsidence or deformation 

 seems hardly candid in face of the facts reported by many 

 Swiss geologists." And he concludes thus : " The citation 

 of the essays by Lincoln and Tarr concerning the Finger 

 Lakes of New York, and the silence concerning such essays 

 as Aeppli's on Lake Zurich, give Wallace's essay an air of 

 special pleading." 



Finding it stated in Professor James Geikie's recent 

 work on "Earth Sculpture" (1898) that he does not 

 know of any valley-lake that has been shown to be 

 formed by earth-movements, and as he is one of the 

 highest authorities on everything connected with glaciers, 

 I requested his judgment as to the special case relied on 

 by my American critic, that of Lake Zurich, as investi- 

 gated by Aeppli. His reply, which I am kindly permitted 

 to quote, is as follows : — 



" It is quite true that geologists have often stated their 

 belief that the great Alpine lakes are due to deformation, 

 but it is seldom that any evidence of deformation is 

 adduced. Yet if the belief were well founded it should 

 not be difficult, by means of maps and accurately drawn 

 sections, to show that it is so. According to Professor 

 Heim, the older quaternary deposits along the base of the 

 Alps, in the region occupied by Lakes Constance and 

 Zurich, have been affected by a flat geo-anticline (about 

 300 — 400 metres in height). If this broad fold had any 

 effect in deforming the valley-bottoms, Ave should expect 

 tectonic hollows to appear in these just above {i.e., higher 

 up the valleys than) the flat swelling. But, as Professor 

 Penck has pointed out, both Lake Constance and Lake 

 Zurich extend right across the geo-anticline — the latter 

 lake attaining its greatest depth near the back of the 

 broad arch. That the valley of the Linth has been dis- 

 turbed by crustal movement in early Pleistocene times is 



