464 Reports and Proceedings—British Association— 
The geographical distribution of the aqueous deposits which are 
associated with the stony clays is somewhat similar. They are very 
sparingly developed in districts where the Boulder-clays are thin. 
Thus they are either wanting, or only occur sporadically in thin 
irregular beds, in the high grounds of Northern Europe generally. 
Further south, however, they gradually acquire more importance 
until in the peripheral regions of the drift-covered tracts they come 
to equal and eventually to surpass the Boulder-clays in prominence. 
These latter, in fact, at last cease to appear, and the whole bulk of 
the “diluvium ” along the southern margin of the drift area appears 
to consist of aqueous accumulations alone. 
The explanations of these facts advanced by German geologists 
are quite in accordance with the views which have long been held 
by glacialists elsewhere, and have been tersely summed up by Dr. 
Jentzsch.' The northern regions, he says, were the feeding-grounds 
of the inland ice. In those regions melting was at a minimum, while 
the grinding action of the ice was most effective. Here, therefore, 
erosion reached its maximum—ground-moraine or Boulder-clay being 
unable to accumulate to any thickness. Further south melting 
greatly increased, while ground-moraine at the same time tended to 
accumulate—the conjoint action of glacier-ice and sub-Glacial water 
resulting in the complex drifts of the peripheral area. In the 
disposition and appearance of the aqueous deposits of the “ diluvium ” 
we have evidence of an extensive sub-Glacial water-circulation— 
glacier-mills that gave rise to ‘giants’ kettles’”’—chains of sub- 
glacial lakes in which fine clays gathered—streams and rivers that 
flowed in tunnels under the ice, and whose courses were paved with 
sand and gravel. Nowhere do German geologists find any evidence 
of marine action. On the contrary, the dove-tailing and interosculation 
of Boulder-clay with aqueous deposits are explained by the relation 
of the ice to the surface over which it flowed. Throughout the 
peripheral area it did not rest so continuously upon the ground as 
was the case in the inner region of maximum erosion. In many 
places it was tunnelled by rapid streams and rivers, and here and 
there it arched over sub-Glacial lakes, so that accumulation of ground- 
moraine proceeded side by side with the formation of aqueous sedi- 
ments. Much of that ground-moraine is of the usual tough and 
hard-pressed character, but here and there it is somewhat less 
coherent and even silt-like. Now a study of the ground-moraines 
of modern glaciers affords us a reasonable explanation of such 
differences. Dr. Briickner? has shown that in many places the 
ground-moraine of Alpine glaciers is included in the bottom of the 
ice itself. The ground-moraine, he says, frequently appears as an 
ice-stratum abundantly impregnated with silt and rock-fragments— 
it is like a conglomerate or breccia which has ice for its binding 
material. When this ground-moraine melts out of the ice—no 
running water being present—it forms a layer of unstratified silt or 
1 Jahrb. d. kénigl. preuss. geologischen Landesanstalt fiir 1884, p. 438. 
2 Die Vergletscherung des Salzachgebietes, etc.: Geographische Abhandlungen 
herausgegeben y. A. Penck, band i. hett 1. 
