Prof. James Geikie’s Address. , 471. 
from the northern inland ice and the mers de glace of the Alpine 
lands of Central Hurope. Another suggestion is that much of the 
material of the loss may have been derived from the denudation of 
the Boulder-clays by flood-water, during the closing stages of the 
last cold period. It is pointed out that in some regions at least the 
léss is underlaid by a layer of erratics, which are believed to be 
the residue of the denuded Boulder-clay. We are reminded by 
Klockmann! and Wahnschaffe*® that the inland ice must have acted 
as a great dam, and that wide areas in Germany, etc., would be 
flooded, partly by water derived from the melting inland ice, and 
partly by waters flowing north from the hilly tracts of Middle 
Germany. In the great basins thus formed there would be a com- 
mingling of fine silt-material derived from north and south, which 
_ would necessarily come to form a deposit having much the same 
character throughout. 
From what I have myself seen of the léss in various parts of 
Germany, and from all that I have gathered from reading and in 
conversation with those who have worked over ldss-covered regions, 
I incline to the opinion that loss is for the most part of aqueous 
origin. In many cases this can be demonstrated, as by the occurrence 
of bedding and the intercalation of layers of stones, sand, gravel, ete., 
in the deposit; again, by the not infrequent appearance of fresh- 
water shells; but, perhaps, chiefly by the remarkable uniformity of 
character which the léss itself displays. It seems to me reasonable 
also to believe that the flood-waters of Glacial times must needs have 
been highly charged with finely-divided sediment, and that such 
sediment would be spread over wide regions in the low grounds— 
in the slack-waters of the great rivers and in the innumerable 
temporary lakes which occupied, or partly occupied, many of the 
valleys and depressions of the land. There are different kinds of 
loss or léss-like deposits, however, and all need not have been formed 
in the same way. Probably some may have been derived, as Wahn- 
schaffe has suggested, from the denudation of Boulder-clay. Possibly, 
also, some léss may owe its origin to the action of rain upon the 
stony clays, producing what we in this country would call “ rain- 
wash.” There are other accumulations, however, which no aqueous 
theory will satisfactorily explain. Under this category comes much 
of the so-called Bergléss, with its. abundant land-shells, and its 
generally unstratified character. It seems likely that such loss is 
simply the result of subaerial action, and owes its origin to rain, 
frost, and wind acting upon the superficial formations, and rearranging 
their finer-grained constituents. And it is quite possible that the 
upper portion of much of the loss of the lower grounds may have 
been reworked in the same way. But I confess I cannot yet find 
in the facts adduced by German geologists any evidence of a dry-as- 
dust epoch having obtained in Hurope during any stage of the 
Pleistocene period. The geographical position of our continent 
seems to me to forbid the possibility of such climatic conditions, 
1 Klockmann: Jahrb. d. k. preuss, geol. Landesanstalt fiir 1883, p. 262. 
* Wahnschaffe : up. cit. and Zeitschr. d, deutsch, geol. Ges, 1886, p. 367. 
