Vol. 58. | SUBALPINE FRANCE AND SWITZERLAND. 469 
the bed of the Limmat Valley, as indeed was proved by the 
difficulties of distinguishing them at Hongg and Baden. It had 
once been much more extensive, the isolated patches on the map 
having been, in many cases at least, formerly continuous. 
Postscript to Discussion. 
[The AurHor, in regretting his unavoidable absence, and thanking 
Prof. Bonney for his kindness in more fully explaining the subject 
of the paper to the meeting, observes that, no doubt, during the 
long inter-Glacial (Upper Pleistocene) Period which followed upon 
the first glaciation, erosion and denudation on the one hand, 
and deposition on the other, went on part passu, the plateau- 
gravel being thus, by re-transport, gradually carried farther out 
and deposited in the lowland valleys as these were being deepened. 
In that sense, the Glacial, Glacio-Fluviatile, and inter-Glacial gravels, 
deposited in the interval between two glaciations, may be said to 
form groups, rather than constitute one single formation. With 
regard to Prof. Bonney’s view that the present Zurich lake-basin 
may have been formed after, and not before, the second glaciation, 
there are, in the Author’s view, various reasons for and against 
it; he proposes to revert to the very complex question.of the age 
of the Subalpine lake-basins in a future paper. 
In reply to the Rev. EK. Hill’s inquiry as to the age of the 
deflection of the River Sihl (by a moraine-wall) from its original 
outlet into the Linth (or Zurich Lake) Valley, the Author holds 
that the present Sihl Valley, running parallel to the present lake 
from the point of deflection to its junction with the Limmat below 
Zurich, is post-Glacial, and affords an instructive instance of the 
remarkable erosive power of a comparatively small river, which has 
already cut its new bed in moraine, gravel, and Molasse to a depth 
of more than 100 metres, and is chiefly responsible for the rapid 
denudation of the Uetli range. 
In reply to Mr. Monckton’s and Prof. Sollas’s remarks, the 
Author observes that if the evidence adduced by him of the 
existence of a Subalpine Molasse-plateau at the advent of the first 
glaciation is correct, the Limmat Valley could not have been filled 
with ice at the time when the Uetli Deckenschotter was deposited. 
He agrees with Prof. Bonney that the moraine underlying the 
Uetliberg Deckenschotter does not point to the presence of a large 
body of ice, such as the glaciers of the second or maximum glaciation 
which filled the then excavated valleys and, passing in many 
places over the Deckenschotter-cliffs, left large masses of moraine 
overlying the same.’ 
With reference to the views of Swiss geologists on the subject of 
1 As, for example, in Northern Switzerland on Albis, Heitersberg (depth of 
overlying moraine = 150 to 300 feet), Bruggerberg, Siggenberg, Mount Irschel, 
and Berg, near Rheinfelden ; and in the Rhone Valley generally, throughout 
its whole length from Lausanne to Lyons. 
ey. G9, No, 2351. DK 
