( -^29 ) 



But when ^ve compare the descriptions of Prof, van Calker with 

 those of the terminal- and bottom moraines of other countries, it appears 

 doubtful whether even that part of Groningen examined by van 

 Calker, notwithstanding its "tremendous accumulation of stones and 

 large boulders", deserves the name of terminal moraine, and may not 

 in fact rather be considered as a bottom-moraine^). It can only have 

 been the shape and direction of the Hondsrug and the presence of 

 the numerous erratics found at its surface, which induced Prof, van 

 Calker and others to regard this steep ridge of the Drenthe plateau 

 as a terminal moraine. Of its internal structure, except for the portion 

 which terminates in Groningen, no notice had beeii taken. 



However in 1891, Lorie, after his exploration of the high peat- 

 moss of Schoonoord, already expressed the opinion that those who 

 had really visited and explored the Hondsrug were not justified in 

 calling it a terminal moraine. He considers it to be the border of the 

 Drenthe plateau, slightly folded back by the moving ice-sheet '). 



A few years ago I had several opportunities of visiting those parts 

 and making the exploration alluded to by Lorie. To me it became 

 quite evident that the Hondsrug in Drenthe is not a terminal moraine. 

 Its geological structure, which I investigated more closely over the 

 Southern half of its length in Drenthe and but partially over its 

 Northern half, entirely refutes this interpretation. I found its nucleus 

 not composed of morainic material, but to be of fluviatile orighi and 

 to consist of Rhenish Diluvium^) At the same time I also observed 

 that this fluviatile nucleus — although but slightly — was distinctly 

 vaulted. The second problem therefore to be solved, was to find the 

 cause of this vaulting, about which I could not agree with Lorie, 

 wiio ascribes it to the motion of land-ice from the North-East. I 

 could not admit the possibility of the ice-sheet folding the soil 

 without perceptibly disturbing the nucleus of the fold, for the 

 contortions do not enter deeply into this nucleus; its stratification 

 has, in general, been well preserved. Basing my deductions on the 

 phenomena observed in the ice-sheet of Greenland, to which the 

 diluvial land-ice may be most^aptly compared, 1 proposed several 

 possibilities which might account for this peculiarity. I suggested 

 the possibility of the ice having moved in the longitudinal direction 



1) F. J. P. VAN Calker, De ontwikkeling onzer kennis van den Groninger Houds- 

 rug gedurende de laatste eeuw. Bijdragen tot de kennis van de provincie Groningen, 

 etc. p. 217. Groningen. 1901. 



2) Handelingen van het Derde Nedcrl. Natuur- en Geneeskundig Congres, 1891. 

 pp. 347 and 349. 



3) These Proceedings, V, p. 93— lU. 



30* 



