Drift of the North German Lowland.—Salishury. 303 
constitutes ‘upper till’ (oberer Geschiebemergel), so the wpper- 
most layer of sand, if it overlie the uppermost layer of second 
glacial till, or if it be the stratigraphic equivalent of that which 
overlies the uppermost layer of second glacial till, is ‘‘upper 
sand” (oberer Sand), All second glacial sands which lie between 
beds of second glacial till,or below the lowest of them,are classed 
with first glacial and inter-glacial sand, as ‘‘lower sand” (witerer 
Sand). The infelicity of this classification and nomenclature is 
alluded to by Dr. Wahnschaffe, although it has been found to be 
a classification which is serviceable in mapping. Interpretations 
have changed since the existing nomenclature was adopted, but 
the nomenclature has not changed to correspond with the newer 
interpretations. 
The ‘‘upper bowlder-bearing sand” often immediately overlies 
a layer of bowlderless, stratified sand, whose proper stratigraphic 
position is said to be beneath the «‘upper till.”” This stratified sand 
is not understood to be ‘‘upper sand.” Because of this strati- 
graphic relationship, the bowlder-bearing sand at the surface is 
looked upon as the remnant of a layer of ‘‘upper till” which has 
escaped removal at the hands of glacio-natant and post-glacial 
waters, while the finer clayey parts of the till were carried away. 
In this case therefore the ‘‘upper sand” is a remnant of the 
‘upper till” and is really its equivalent. We do not understand 
that the uppermost bed of till, lying below ‘:upper sand,” but 
separated from it by a bed of stratified sand, whose stratigraphi- 
cal position is below the ‘‘upper till,” would be classed as ‘‘upper 
till,” even though it be the uppermost existing bed of second 
glacial till. The idea that the ‘‘upper sand’’-is aresidue of ‘‘up- 
per till,’ formed as indicated, seems to be a prevalent one. — It is 
in this category that Dr. Wahnschaffe places the bowlder-bearing 
sand which covers the ‘‘Luneburger Heide.” As already indicated 
the reasons given for such reference (p. 96) do not appear to me 
to be conclusive. Indeed none of the reasons assigned for be- 
lieving that the ice, in its second invasion, crossed the Elbe in 
western Germany, seem to me to carry conviction. 
Dr. Wahnschaffe, as well as other German glacialists, recog- 
nizes the fact that within the formations of second glacial age 
there may be, and in many cases are, several beds of till separated 
from each other by layers of sand and gravel. While American 
glacialists are fully agreed with Dr. Wahnschatfe that several 
