Vol. 58. ] GLACIER-LAKES IN THE CLEVELAND HILLS. 477 
must also be made to the fjord-muds so well described by Rink and 
others, for these muds, though accumulated under tidal conditions, 
must have many features in common with the deposits of glacier- 
lakes. © 
The study of lacustrine formations other than those of glacier- 
lakes is also germane to the present enquiry, for the differences 
will be only in the details, and especially in two of them—the 
amount and character of the mud, and the presence and character 
of included organic remains. Reference may therefore be made to 
the extensive literature of limnology, and especially to Prof. F. 
A. Forel’s monograph ‘Le Léman’ vol. i (1892) pp. 101-1389; 
Dr. H. R. Mill’s valuable description of the English Lakes’; and 
Mr. Upham’s monograph on Lake Agassiz.” 
The Lake of Geneva, which differs from the largest of British 
Pleistocene lakes chiefly in the absence of any direct contact with 
the glaciers that feed it, might be taken as a typical area of 
lacustrine accumulation, and a general description of its floor- 
deposits will be helpful to our understanding of the general 
conditions of deposition. 
At the point where the Rhone debouches into the lake, near 
Villeneuve and Bouverie, the river casts down its great load of 
shingle, and is gradually pushing its mouth forward into the lake. 
Beyond the gravel, finer materials are cast down within a short 
distance of the mouth of the river; and beyond this again the fine 
glacier-mud, with which the Rhone is so heavily charged, is wafted 
on and laid down over a wide area as a deposit of impalpable mud 
of exceeding fineness. The seasonal and diurnal augmentations of 
volume which affect the Rhone, must carry sediments of a different 
grade out to the regions of finest sediment, and so it might be 
anticipated that the fine clays would show interlaminations of 
coarser material. Interlaminations of materials differing more in 
colour than in texture must also occur. The bed of the Lake of 
Geneva is not sufficiently well exposed to enable me to support 
these generalities by actual cbservation, but fine laminated muds 
have been found in the exploration of lake-dwellings in seasons 
of exceptional dryness, when the lake-levels were lowered. 
If the Lake of Geneva were held up by an ice-dam, as the Mirjelen 
See is, we might expect to find stony clays, resembling those of the 
Marjelen See, and perhaps actual moraine, accumulating near the ice; 
while farther away laminated clays might be expected to prevail, 
and to contain occasional stones, large and small, which had been 
rafted out by bergs breaking off from the ice-front or by shore-ice. 
Such sporadic boulders and pebbles do occur sparsely in some of 
the Warps of Yorkshire. 
Some means of distinguishing, however, between the flood-alluvium 
of rivers and these lacustrine deposits seems to be a desideratum, 
and as the result of the examination of a large number of sections 
of river-silt in the magnificent exposures opened in the excavation 
' Geogr. Journ. vol. iv (1894) p. 237. 
* Monogr, U.S. Geol. Surv. vol. xxv (1896). 
