GLACIAL GEOLOGY. 225 



glacial epoch rest here and there upon loess, and he confirms Penck's 

 observations in South Bavaria that this remarkable formation never 

 overlies the morainic accumulations of the latest glacial epoch. Ac- 

 cording to Penck and Briickner therefore the loess is of interglacial age. 

 There can be little doubt, however, that loess does not belong to any one 

 particular horizon. Wahnschaffe* and others have shown that through- 

 out wide areas in north Germany it is the equivalent in age of the 

 " Upper Diluvium," while Schumachert points out that in the Rhine 

 valley it occurs on two separate and distinct horizons. Professor 

 Andrese has likewise shown that there is an upper and lower loss in 

 Alsace, each characterized by its own special fauna.J 



There is still considerable difference of opinion as to the mode of 

 formation of this remarkable accumulation. By many it is considered 

 to be an aqueous deposit; others, following Richthofeu, are of opinion 

 that it is a wind-blown accumulation, while some incline to the belief 

 that it is partly the one and partly the other. Nor do the upholders 

 of these various hypotheses agree amongst themselves as to the pre- 

 cise manner in which water or wind has worked to produce the ob- 

 served results. Thus, amongst the supporters of the aqueous origin of 

 the loess, we tind this attributed to the action of heavy rains washing- 

 over and re-arranging the material of the bowlder clays.§ Many, again, 

 have held it probable that loess is simply the finest loam distributed over 

 the low grounds by the tiood waters that escaped from the northern 

 inland ice and the mers de glace of the Alpine lauds of central Europe. 

 Another suggestion is that much of the material of the loess may have 

 been derived from the denudation of the bowlder clays by flood water 

 during the closing stages of the last cold period. It is pointed out that 

 in some regions at least the loess is underlaid by a layer of erratics, which 

 are believed to be the residue of the denuded bowlder clay. We are re- 

 minded by Kiockmannll and Wahnschaffe^] that the inland ice must have 

 acted as a great dam, and that the wide areas in Germany, etc., would 

 be flooded, partly by water derived from the melting inland ice and 

 partly by waters flowing north from the hilly tracts of middle Germany. 

 In the great basins thus formed there would be a commingling of fine 

 silt material derived from north and south, which would necessarily 

 come to form a deposit having much the same character throughout. 



From what I have myself seen of the loess in various parts of Ger- 

 many, and from all that I have gathered from reading and in conver- 

 sation with those who have worked over loess-covered regions I incline 



* Abhandl. z. tjeolog. Specialkarte v. Preusaen, etc., Bd. vil, Heft 1 : Zeiischr. d. deutsch. 

 gcolog. GeseUsch., 1885, p. 904; 1886, p. 367. 



\ Hygiciiisehe Topographic, von Strasaburg i. E., 1885. 



X Abhandl. z. geolog. Specialkarte v. Elsass-Lothringen, Bd. vii. Heft 2. 



^Laspeyren: ErlMuteruiigen z. gcolog. Specialkarte v. PrcuesHn, etc., lilatt Grtihzig, 

 Zorbig tind I'etersbcrg. 



II Klockmaun : Jahrh. d, k. premn. gcolog. Landesanstalt fiir 1883, p. 262. 



^ Wahnsch after Op. cit. aud Zeitschr. d. deutsch. geolog. Gc9., 1886, p. 367. 



H. Mis. 129 15 



