92 Reports and Proceedings—Geological Society of London. 
2. ‘On the Origin of Valley-Lakes, mainly with reference to the 
Lakes of the Northern Alps.” By the Rev. A. Irving, B.A., B.Sc. 
The author, having given reasons for considering this question still 
an open one, proceeded to criticize Prof. Ramsay’s theory as it was 
expounded by him in 1862. The defects in Prof. Ramsay’s argument 
are, he considers :—(1) the non-recognition of the fact that many lakes 
in the Northern Alps lie in longitudinal valleys; (2) the omission, in 
the discussion of the relation of valleys to lines of fracture, of the 
consideration of anticlinal lines of fracture, which can be shown to be 
very common in the Alps; (3) the illogical inference from conditions 
existing in crystalline metamorphosed rocks as to what could or could not 
appear in the stratified sedimentary deposits of the Alps, among which the 
Alpine lakes chiefly occur; (4) the rejection of the hypothesis of swbs7- 
dence on the mere ground of the number of instances. The author 
proceeded to show that the lakes of the Northern Alps are found, as a 
rule, just among those strata where subsidence would be most likely to 
occur. In this way it was shown that we are not shut up, by Prof. 
Ramsay’s reasoning, to the hypothesis of glacial excavation. 
Further, other agencies than those discussed by Prof. Ramsay may 
have co-operated to form lakes, such as :-— 
(a) Alterations in the relative levels of different parts of a floor of a 
valley, connected with movements of parts of a mountain-system on a 
large scale. The effects of (1) lines of flexure crossing older lines of 
valley-erosion, (2) of lateral thrusts closing in a valley (partly), were | 
here considered. 
(b) Upthrust of the more yielding strata (as in the “creeps” of 
coal-mines) by resolution of torces due to pressure of the mountain- 
masses at the side of a valley. 
(ec) The dead weight of the huge glaciers which filled the Alpine 
valleys, and crushed in the floor, in places where extensive under-ground 
erosion had gone on in preglacial times. 
(d) The partial damming up of valleys, (1) by diluvial detritus, (2) 
by moraines, (3) by Bergstirze (recently investigated by Prof. Heim of 
Ziirich). 
(e) Faults. 
(f) Chemical solution, by Alpine waters derived from the melting of 
the snow, which has undergone long exposure to the atmosphere. 
It was shown that the very situation of the great majority of the 
lakes of the Northern Alps is distinctly favourable to the operation of 
one or more of these agencies. ‘lhe Konigsee was mentioned as a 
special instance of subsidence; the Achensee of a lake lying in a faulted 
line of dislocation; L. Alleghe and L. Derborence as lakes formed by 
Bergstiirze during the last century ; the prehistoric delta of the Arve 
as the most conspicuous instance in the Alps of the partial damming-up 
of a valley by diluvial detritus; the guondam Lake of Reutte as an 
instance connected with violent inversion of strata; and the ancient 
lakes of the Grodner and Oetz Thals as instances of the action of 
moraines. 
The common fact of observation that lakes are more numerous in 
glaciated than in non-glaciated countries, the author thought, was 
partly explained by some of the foregoing principles, partly by the 
