( nv2 ) 



i'ivei'-dihn inin and according lo the antlior himself have come from 

 tiie uppcr-slialiim (p. 94 — 95). 



5'^'. "Boulder-claj and bonldci'-sand are fonnd Jointly or the 

 latlcr alone without liiis being expressed in the form of the surface." 



I cannot subscribe to this. My examination has not yet led to an 

 established opinion, but in some places I can decidedly conclude 

 from (he relief whether we have to do with boulder-sand or with 

 clay. 1 take for example the already mentioned hill near Gasselte, 

 whicii runs nearly in the longitudinal direction of the Hondsrug. At 

 the top we have a thick clay-bed there, which towards the sides 

 passes into a thimier layei-, at the deepest places altogether consisting 

 of boulder-sand. Further observations in this direction are of course 

 absolutely necessary before formulating this rule in general. 



Taking all this into consideration, I am of o})inion that, from the 

 live mentioned reasons, it does not follow that the boulder-sand cannot 

 be washed out from the clay. In my opinion the author has not 

 taken either of the two ways in which this problem can possibly 

 be solved : 



1"^ the comparative mechanical analysis of boulder-sand and bonl- 

 der-clay ; 



2"^' the study of the general petrographical nature and the charac- 

 teristics of the surface of the enclosed stones. Nothing has been said 

 about this, whereas it seems to me that only in this way it might 

 pi'rhaps be proved whether that is to be looked upon as inner- 

 giacial-moraine and not as washed out gronnd-moraine. 



Taking all this together it gives sullicient proof that the superficial 

 structure of the Houdsrug does not corresj>oud with Dubois's opinion. 

 The direction of the glacial tlow dei-ived from this opinion is not 

 supported by anything, apart from the piece of quartzite about which 

 I have little to say. In my opinioji oidy one observation like this 

 has but very little value ; a greatei' number of course woidd be of 

 great importance. 



Moreover as regards the possibility of a deviation of the direction 

 of the Scandinavian glacial tlow owing to that of Scotland, I wish 

 to make the following remark : 



Not without some surprise have 1 noticed that Dubois represents the 

 glacial tlow from Sweden as moving first in a South-tveiite?'» direction 

 to reach our country over Denmark, though one of the principal 

 results of the examination of our boulders by K. Martin, van Calkkh 

 and SciiROEDKR van der Kolk is that the glacial tlow which has 

 produced the glacial diluvium in the North of the Netherlands has 



