1866.] GOD WIN- AUSTEN BELGIAN TERTI ARIES. 253 



pression of the line of the axis of the country, partly by the eleva- 

 tion of the district north of it (Brabant and Hesbaye) ; but had the 

 valley of the Mouse existed as it is now, at the time of the dispersion 

 of the Ardennes pebbles, or of the accumulation of the Loss, it must 

 necessarily have been choked by them ; but the very reverse is the 

 case, and that valley (which is a line of fracture) may be safely 

 pointed out as the line of one of the changes of relative level which 

 have happeued since the later Glacial Period. 



Should the supposition be correct as to the source of the Arden- 

 nais pebbles, the disintegration of the surface by which the pebbles 

 of the " Poudingue de Burnot" were set free along the slopes of the 

 Ardennes, must be referred to the period of greatest elevation, of 

 cold, and great river-courses ; the larger and coarser accumulations 

 connected with the line of the Meuse from Liege having been brought 

 down by the Ourte and the Amble ve. The quartz pebbles of the 

 line of the Meuse having come from the upper sources of the Lesse, 

 are of less size, inasmuch as the streams are smaller. 



In like manner the Loss was the deposit of the turbid waters which, 

 at the break up of every winter, periodically accumulated over the 

 low area (now part of Brabant and the Hesbaye) between the slopes 

 of the Condroz and the Dune sands from the coast. 



Viewed in this light, the Belgian area seems to offer some very 

 interesting illustrations of the varying conditions of the last great 

 Glacial Period. 



7. Sangatte Beach. — Before leaving the geological phenomena be- 

 longing to this period, I would briefly call attention to a few points 

 connected with the section of the coast from Sangatte, — a section of 

 very great interest, relative to which Mr. Prestwich has recently 

 given a second paper, and which we visited together. 



At the base of a vertical cliff of chalk there is a coarse shingle 

 beach, and a little in advance of it are horizontal sands, with a few 

 flint pebbles ; these are of marine origin, and the section corre- 

 sponds with that at the base of the subaerial beds at Eottingdean 

 and Brighton. 



Above the marine sand and shingle is a black band, occasionally 

 very strongly marked, the evidence of an old terrestrial surface. 

 The level of the old coast-line was very little above the present, but 

 subsequently there must have been a rise, to what extent cannot 

 here be determined ; but the subsequent accumulations all indicate 

 subaerial conditions. 



Above all are blown sands ; next below these, near Sangatte, is 

 an angular debris of flints, with blocks of ferruginous sandstone, fol- 

 lowing the coast-line ; layers of Loss succeed, with occasional flints, 

 also land shells. The thickness of the beds of sandy Loss and of 

 loam (as of the angular materials) increases in the direction of the 

 chalk hills, and at last the mass passes by alternations from earthy 

 Loss to chalky marl, and seams of chalk nodules; these become a 

 chalk rubble ; and angular blocks of chalk of considerable size, 

 have been accumulated against and at the foot of the old clifl", and' 

 above the marine beds. 



