1866.] G0DWIN-ATJ8TEN BELGIAN TERTIABIES. 251 



their equivalents, the peat-growths. However, there may stiU be 

 a great range between these extreme periods. 



In like manner the Loss overlies the gravel beds in which the frag- 

 mentary remains of the great Pachyderm fauna occur. 



Both the Campine sands and the Loss are subsequent accumula- 

 tions to the Ardennes quartz pebbles ; but the occurrence of these 

 pebbles at the base of both does not necessarily connect them with 

 either, but it suggests that these two accumulations must be nearly 

 of the same age ; and such, it seems, was M. Dumont's latest view. 



The presence of quartz pebbles in the detrital beds at Fort 4 sup- 

 plies another link to the chronology. 



To what extent the surface of Belgium was submerged during the 

 Glacial Period cannot easily be determined, owing to the thick 

 coverings of subsequent date. Antwerp probably marks very nearly 

 its marginal line ; and this agrees very well with the range of the 

 true "Boulder Formation" with northern rocks extending from 

 Amheim to Groningen and into Hanover. If the fine sands (Zand 

 diluvium) which in North Holland form the overlying portions of the 

 Boulder-formation, be connected with the Campine sands of South 

 Holland and Belgium, they present a line parallel vdth that of the 

 Boulder- coast ; and then, as all their characters would indicate, they 

 might be the blown sands from the marginal beds of that period, 

 and of that stage of it when the Northern Hemisphere began to re- 

 emerge — a process which took place from south to north. 



4. Loss. — During our visit we came upon good illustrations of the 

 superficial layer known in Belgium as the " Limon de Hisbaye." 



It occurs at considerable elevations to the north of the Sambre 

 and Meuse, along the line from Liege to Namur and north of 

 Charleroi ; but it does not rise to corresponding elevations on the 

 south of those rivers, on which side, though of great thickness, it is 

 at low levels. During the excursion of 1852 we saw a thick ac- 

 cumulation, with JSuccinea ohlonga and Pupce, at Audregnies ; and 

 this year I saw good sections of it, both above Namnr and about 

 Gembloux. From Liege westwards the Loss may generally be sepa- 

 rated from any beds it may overlie by the presence of a seam of 

 quartz pebbles. 



The land-shells cited above are not commonly met with, but they 

 increase in frequency towards the line of the Ardennes. The Loss in 

 its arrangement, when in great masses, shows that it has been de- 

 posited by water. The " Sable de Campine " and the " Limon de 

 Hisbaye " form, as was long since said by M. Omalius, the " man- 

 teau de la Belgique." The two accumulations have never been 

 noticed to overlap, they rather pass into one another, along a line 

 from west to east, the sands being to the north and the fresh-water 

 Loss to the south. The opinion of M. Dumont, that they were 

 somewhat synchronous, has been alluded to. 



5. Polder Mud.— The Polders, or brackish- water mud-flats of 

 the low coast of Belgium and Holland reach up on either side of the 

 Scheldt as far as Antwerp. This is the most recent sedimentary 

 formation we saw, consisting of blue mud, as may be seen in the 



T-2 



