Prof. Baron F. Eichthofcn — On the Origin of the Loess. 301 



formed by tlie same process of long-continued subaerial deposition 

 of dust on steppes as that of the eastern continent, and the argu- 

 ments which I had applied to this appeared to me to be no less 

 valid for the Loess regions of North and South America. 



The Loess-covered portions of Europe extend, as is well known, 

 from the Pj'renees, the Alps, and the Balkan in the south to 

 Belgium, the North German plains and Poland in the north, and 

 from southern France in the west to bej'ond the limits of the 

 continent in the east. Every portion of this entire I'egion must 

 have had the character of a steppe during a sufficient length of 

 time to allow the deposit to be formed in at least such thickness 

 as we 'Observe at present. This thickness increases on an average 

 as we proceed from north-west to south-east. It appears that, 

 while east of the Alps the beginning of the steppe era may have 

 been of earlier date, it commenced in Galicia, Germany and France 

 during, or shortly after, the time of most extensive glaciation, and 

 that one or the other kind of steppe was formed on the ground of 

 the moraines as they were gradually laid bare by the retiring of the 

 lowland glaciers. When Europe had its north-western limit beyond 

 the present bathymetrical line of one hundred fathoms, and the 

 summit line of the Alps was at greater elevation than at present, 

 a continental climate must have prevailed such as is the prime 

 condition for the formation of steppes, and it is probable that these 

 had then their widest extent in a north-westerly direction. It would 

 lead me too far now to explain why it appears that the conditions 

 of climate, vegetation and animal life prevailing north of the Alps, 

 after having gone through a stage resembling that of the tundras, 

 must have been intermediate in character between those existing 

 at the present time in Siberia and those prevailing in Southern 

 Russia, while various evidence goes to show that farther south- 

 east, in the Hungarian and Eoumanian basins, there was no drainage 

 to the sea, and the steppes of these countries resembled those of the 

 drainless regions of Asia. 



Gradually, when, with the renewed intrusion of the sea upon the 

 land, the continental climate of Central Europe was converted into an 

 oceanic climate, the change progressing slowly in the direction from 

 north-west to south-east, the growth of the Loess ceased in the 

 north-west, while it still continued in the south-east. Even now 

 the soil is growing where it is covered by vegetation and sheltered 

 from erosion. But the process is extremely slow and, with the 

 exception of Southern Russia, is no longer regional, places of 

 subaerial deposition being scattered among others of erosion. 



At the same time when I published these arguments regarding the 

 mode of origin of the Loess of Europe, Dr. Nehring, of Wolfen- 

 biittel, came in the course of his admirable researches on the bones 

 found in the Loess of Northern Germany to the well-known result, 

 that the mammals which lived there at the time of the formation 

 of that earth were identical with, or nearly related to, those which 

 are living now on the steppes of Arctic regions, as well as in Siberia 

 and Central Asia, and he concluded, that Germany must then have 



