PLEISTOCENE LOAMY DEPOSITS. 165 



waters either of the sea or of violent inundations and dibdcles. 

 In his opinion only glacier-ice could have produced the peculiar 

 contour to which he refers. The limon biefeux, he concludes, is 

 a true glacier-mud which has heen formed underneath ice and 

 left lying upon the surface at the time when the glaciers or ice- 

 sheet melted away. It is essentially of local origin, and in its 

 composition always reflects the character of the strata in the 

 immediate neighbourhood of which it occurs. The limon biefeux 

 of Picardy, according to M. de Mercey, corresponds to the yellow 

 clay with stones and blocks which M. Dupont has described as 

 covering certain regions in Belgium. The overlying brick-clay 

 he would assign, as already mentioned, to the subsequent 

 action of water, etc., washing, sifting, and re-arranging the mate- 

 rials of the limon bitfeux. 



M. de Mercey's views have been controverted at considerable 

 length by M. E. d'Acy, 1 who maintains that both the lower and 

 the upper loams of the north of France are the result of a 

 great diluvial cataclysm, as M. Belgrand has maintained, 2 and 

 that this cataclysm took place in Pleistocene times and after the 

 valleys had been excavated. He appears to me to have shown 

 that Mercey's contention that the limon biefeux is of the nature 

 of a moraine profonde or subglacial mud is hardly well sup- 

 ported, but he has not satisfactorily disposed of the evidence 

 which, as M. de Mercey has indicated, goes to prove that the 

 limon biefeux was accumulated under cold conditions of climate. 

 But to this point I will return in the sequel. 



An entirely novel view of the origin of loss has been ad- 

 vanced by Baron Bichthofen, and amply illustrated in his great 

 work on China. A deposit similar in all respects to the Rhenish 

 and Danubian loss covers vast areas in that country. It differs 

 from the loss of Europe only in its greater vertical and hori- 

 zontal extent. Bichthofen describes it as forming cliffs or bluffs 

 on the Yellow Biver, which in some places rise to a height of 



1 Le Limon des Plateaux du Nord de la France et les silex travailUs qu'il ren- 

 ferme (1878). 



2 La Seine, L Le Bassin Parisien aux Ages Anteliistoriques, p. 216 ; Compt. 

 Bend. Congr. Intern..d'Anthrop., etc., Bruxelles (1872), p. 131. 



