( 99) 
1 M. in length. Estimating the air spaces between the stones heaped 
up at '/,, we find about */,, of the volume of the boulder-sand bed 
to have consisted in stones. Between pit XV and XVI a similar 
1 
24 
estimate, from a surface of 484 M’., leads to for that proportion. 
What an enormous thickness of boulder-clay, which in this region 
is particularly poor in stones, must have been washed out to leave 
all these stones! 
ged The boulder-sand contains very little flint, the boulder-clay very 
much, everywhere. Flint is the kind of rock most frequently occurring 
in the clay (Odoorn, Zwinderen, Nieuw-Amsterdam, Mirdummer-Klit, 
Nicolaasga, Steenwijkerwold, Wieringhen etc.) 
4th Even the deepest and evidently not washed out parts of the 
boulder-sand, which rest immediately on the Rhine-sand, are as a rule 
poor in clay. 
5th Boulder-clay and boulder-sand are found jointly or the latter 
alone without this being expressed in the form of the surface. 
That the Hondsrug cannot be a terminal moraine, as has been 
supposed by some geologists, follows sufficiently from the description 
of its structure as given above. 
It neither can owe its’ origin to an upward folding or pressing 
of the underground, perpendicular to the direction of the motion of 
the pleistocene land-ice; for how then to account ‘for the deposition 
of boulder-clay parallel to the Hondsrug ridge? 
The distribution of the boulder-clay in our north-eastern provinces 
is so, that there can hardly be any doubt that from the beginning 
it has been very unequal and the boulder-clay has been laid down 
parallel with the actual Hondsrug ridge. 
Can it perhaps by its weight have pressed upward the Rhine-sand, 
when the soil was still totally drenched with melting-water? This 
apparently has not been possible. The specific weight of a well 
compressed sample of that Rhine-sand from the Hondsrug, quite 
drenched with water, is 2.05. If now that of the boulder-clay had 
even attained the high value of 2.5, it would require a bed of 
boulder-clay of a thickness of 20 M. to cause an uplifting of 5 M., 
as is the average height of the Hondsrug above the surrounding 
'/, of that 
region. In reality the thickness is most probably only * 
supposed value. 
Other causes must have been in action to bring about this elevation 
of the Hondsrug, but causes which nevertheless were not inconsistent 
with the deposition of the boulder-clay parallel to that ridge. 
These causes may be found in what CHAMBERLIN, RUSSELL, SALISBURY, 
VON Drrycarskr and already Nansen have taught us regarding the 
