292 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



The tripartite arrangement of the Ehine diluvium, Nos. 1, 2, and 

 3, can be followed southward as they rise inland, the middle bed 

 consisting of fine sand, loam, and peat beds. It is thus evidently the 

 equivalent of the Tegelen stage, and the upper Ehine diluvium cor- 

 responds to the chief terrace, which is confirmed by its position 

 immediately beneath the marine beds of the Eem zone. Its fluvio- 

 glacial origin is shown even here by bowlders of granite and other 

 rocks of northern origin, and also, according to P. Tesch (30) by the 

 large quantities of feldspar crystals, orthoclase, and microcline which 

 can only have resulted from the disintegration of granite rocks. 



The fluvio-glacial origin of the lower Rhine diluvium, first main- 

 tained by Dubois, is more doubtful, for erratics of northern origin 

 are extremely rare in it, though Lorie found pebbles of northern 

 granite in a boring at Utrecht at 10-i and 151 meters, and in a bor- 

 ing at Gorkum at 117 meters below sea level. Tesch concludes that 

 the gravels are really fluvio-glacial, containing a considerable amount 

 of northern material, but the ice edge lay some distance off, and the 

 granite mostly became disintegrated into quartz and feldspar before 

 coming to rest in the Rhine-Meuse delta. 



SUMMARY, 



The succession of events in Holland may now be outlined with 

 considerable confidence as follows : 



Preglacial. — In preglacial times the Rhine, like the rivers of north 

 Germany, cut its bed below present sea level, indicating elevation 

 above the present. At the beginning of the first glacial period the 

 land began to sink. 



First glacial period. — Lower gravel diluvium of Rhine, and grav- 

 els of Rhine-Meuse delta, with occasional bowlders rarely erratics 

 of northern material, but a considerable amount of feldspar, prob- 

 ably northern. The ice must have lain some distance off to the north- 

 east, but owing probably to a relative elevation of Scandinavia, the 

 thaw-water channel ran across the mouth of the Rhine-Meuse delta. 



First interglacial period. — A slight elevation, combined with a de- 

 crease in the amount of water brought down by the two rivers, al- 

 lowed the formation of the plant-bearing clays of Tegelen, and their 

 equivalents at Wylerberg and in the clays and peats of the middle 

 division of the Rhine diluvium. Farther upstream the formation 

 of the older gravel terraces ceased and the rivers eroded their valleys 

 somewhat. 



Second glacial. — The land ice reached the Rhine Valley, and 

 formed the terminal moraines and ground moraine of the maximum 

 glaciation of Holland. The land sank again slightly, and the gravels 

 of the chief terrace and of the upper coarse Rhine diluvium were de- 



