Drift of the North German Lowland.—Salishury. 297 
cognizance of the facts which are established by observation, and 
in their stead to start from premises which have nothing to do 
with the problem in hand. The result is that mathematics, by 
very painstaking methods, sometimes reaches results which are 
altogether without value for the explanation of the real relations 
of ‘things:” (p. 62.) 
Stria. One of the striking differences between the glacial 
phenomena of Germany and America is the paucity of striz in 
the former country. The ice there invaded territory whose 
formations belong largely to the Cretaceous, Eocene and Neocene 
periods. They are unindurated and therefore not adapted to the 
reception and retention of striz. These formations contributed 
generously to the drift, and were finally deeply buried by it, so 
that rock exposures are relatively rare. The strong contrast be- 
tween the two countries in the matter of strizcan hardly be more 
forcibly illustrated than by indicating that within the space of ten 
pages the striae of each known locality in Germany are not only 
mentioned, but discussed, as well as such other phenomena of 
glaciation,— planation, polishing, roches moutonnées, ete.,— as 
are intimately connected with striz. Since striz on bed rock, and 
their accompaniments were at the outset regarded as the most 
convincing proof of an ice sheet, and since the surface inferior 
to the drift in Germany is rarely exposed, and since these ex- 
posures are rarely of such material as to exhibit strive, planation, 
ete., it is not strange that the glacier hypothesis did not find so 
ready acceptance in Germany as in our own country. 
Til mainly subglacial. The till of Germany Dr. Wahnschatfe 
regards as almost wholly subglacial. While admitting the possi- 
bility of superglacial till, he does not regard it as having any 
considerable development in Germany. In this respect Dr. Walhn- 
schatfe’s opinion is sharply in contrast with that of some Ameri- 
‘an geologists, who hold to the idea of very considerable thick- 
nesses of superglacial till overlying the subglacial, and in con- 
sonance with the view of other American geologists who believe 
that superglacial material has but relatively slight development in 
our country, The reasons assigned (pp. 82-3) by Dr. Wahn- 
schatfe for classifying essentially all the till as subglacial, would 
not be of force as applied to material transferred from a sub- 
glacial to a superglacial position, if such transference takes place, 
And such transference is assumed to be possible (p. 86). The 
