Vol. 58.] IN SUBALPINE FRANCE AND SWITZERLAND. 467 
and that the rise of temperature corresponding to that subsidence 
would not be more than 2° Cent. or 3°6° Fahr., which is about 
equal to the difference between the present mean Subalpine 
temperature north and south of the Alps,’ for example between 
Zurich and Lugano (9° and 11° Cent. respectively), and would 
be insufficient to affect materially the conditions under which a 
general advance of the ice might take place. Whether the zonal 
subsidence, and, with it, the formation of the present lake-basins, 
must be assigned to the first or second inter-Glacial Period, or to a 
yet later date, 1is still an open question with which I propose to deal 
in a future paper. 
(5) So far as the immediate scope of the present paper is con- 
cerned, | hope to have shown conclusively that the pre-Glacial 
existence of the principal river-valleys and lake-basins of Subalpine 
France and Switzerland, in their present form and depth, can no 
longer be maintained in face of the evidence of the extensive 
Molasse-plateaux upon which the fluviatile products of the Pliocene 
glaciation were deposited. Equally untenable appears, in face of 
that evidence, the view that the Rhone-Valley conglomerate known 
as ‘alluvion ancienne’ is either pre-Glacial or Quaternary. Deposits 
of such Pliocene Glacio-Fluviatile alluvia abound in the whole region 
between the Jura and the Cevennes above Lyons, in tbe Rhone 
Valley below Lyons, between the Dauphinese Alps and the Cevennes, 
in the Valley of the Po and elsewhere at the base of the Alps; and 
it may safely be averred that the more they are studied, the more 
will the formerly accepted views with regard to their character 
and origin, and to the contour of Alpine and Subalpine valleys 
towards the end of Tertiary times, come to be modified. 
Discussion. 
' Prof. Bonney expressed his regret at the absence of the Author, 
for the paper required a more detailed explanation than could be 
conveyed by an abstract, necessarily condensed. So, as he knew the 
ground, he would venture to state to the Fellows, in a slightly 
different form, the problem which this paper attempted to solve,— 
a problem which, in the speaker’s opinion, was one of the most 
difficult presented by the later geology of the Alps. Having done 
this, he said that the hypothesis, though rather startling in the 
magnitude of the denudation assigned to a single interval in the 
glaciation of the Alps, did remove some difficulties which hitherto 
had been most perplexing. But he thought it possible that some 
of the patches of Deckenschotter might be newer than others, and 
that denudation and deposition might have gone on para passu prior 
to the second advance of the ice. If any part of the Hongg gravel 
* Or the difference between the present mean temperature of districts on the 
same side of the Alps: for example Geneva, Bale, and Lucerne (9°5° Cent.), Berne 
(8°3° Cent.), and St. Gall (7°5° Cent.). 
