342 S. V. Wood — Origin of the Loess. 



mergence, which reached the elevation at which it is traceable in 

 the South of England, should not have extended some way over the 

 North-west of France ; and indeed gravels occur there which appear 

 referable to this, though, as is the case with the South of England, 

 the action of the waves during emergence have removed all but a 

 few patches of such gravel which now remain to show its original 

 outspread on this sea-bottom. 



Over the portion of France, therefore, where this submergence 

 extended, the area beneath the line of it would be destitute of this 

 atmospheric formation of the major glaciation, in the same way that 

 the corresponding part of England is ; but the similar formation 

 resulting from the agency in question during the minor glaciation 

 would occur there ; and this I take to be the limon, or brick-earth, 

 which covers the lower chalk plateaux of Picardy, and which wrap- 

 ping over the Picardy valley slopes is the same, M. de Mercey 

 says,^ as covers the Cyrena gravel of the Somme Valley, and buries 

 the old Picardy shore-line, that is to say, the shingle and cliff" of 

 Sangatte, near Calais, thus corresponding with the material under 

 which the ancient cliffs of Brighton, Isle of Wight Foreland, Port- 

 land, and Sili Bay in Glamorganshire are buried, which, like the 

 Picardy limon, is full of angular fragments of flint in the chalk 

 districts, and of other stone elsewhere, due to the shattering effect of 

 intense frost acting on the moisture which penetrates even solid flint. 



The Loess seems to occur throughout all that part of the Northern 

 hemisphere which falls within those latitudes which must have had 

 an Arctic climate during the Glacial period, and through that part 

 only ; the molluscan remains which it has yielded being those of 

 land-shells alone. The land-ice from the moraine of which most of 

 the Glacial clays have originated, and which protected the land sur- 

 face from the agency in question, was confined to those regions, such 

 as Scandinavia, Ireland, Scotland, and the Northern part of England, 

 where, though the mountains were of small altitude, they were close 

 to the source of the snow — the Sea, or to those more inland regions 

 where the greater mass and elevation of the mountains caused the 

 fall of greater volumes of snow than the summer sun could remove, 

 and which therefore invaded and overwhelmed the low grounds. 

 Bej'ond these regions, and embracing by far the larger part of the 

 Europeo-Asiatic continent, were those where the snowfall was less 

 than the summer sun could remove, and consequently no land ice ; 

 and here, under the intense Siberian-like climate of the time, the 

 action in question went on. In North America the Loess extends 

 apparently over the region drained by the Mississippi and its 

 numerous tributaries, and sets in where the evidences of the 

 land ice, which seems to have filled the whole of St. Lawrence and 



1 Bulletin de la Societe Linneenne dii JSTord de la France, p. 303, As M. de 

 Mercey describes this limon as reaching from nearly the bottoms of the valleys in 

 Picardy to elevations of more than 200 metres, and on the plateaux as attaining a 

 thickness of 30 metres, I infer that part of it, like the clay with flints in England, 

 originated chiefly during the major glaciation on that part of the chalk with flints 

 which was above the Line of submergence during some part at least of the period of 

 ■ this glaciation. 



