1 877.] The Loess of the Rhine and the Danube. 67 
hand will doubtless be elaborated in its details, and may 
perhaps here and there be somewhat modified. But we 
shall all feel that Alfred Russel Wallace is the architect 
whose designs we are carrying out. 
V, ON THE LOESS OF THE RHINE AND 
THE DANUBE. 
By Thomas Belt, F.G.S. 
t HE sides of the valleys of the Rhine and the Danube, 
as well as those of their tributaries, are covered with 
a yellowish grey calcareous clay up to a height of 
several hundred feet above the rivers. This clay is often of 
great depth, is unstratified, and contains land and fresh- 
water shells scattered throughout it. It also contains the 
bones and the stone implements of palaeolithic man, and 
the remains of the mammoth, the woolly rhinoceros, and 
other Mammalia. This clay has been named the Loess, 
and respecting its origin and its relation to the excavation 
of the great valleys there is much difference of opinion. 
Sir Charles Lyell, in commencing an able summary of the 
faCts respecting the distribution of this deposit, states that 
skilful geologists peculiarly well acquainted with the physical 
geography of Europe have styled the loess the most difficult 
geological problem.* It is certainly curious to contrast the 
ease with which some philosophers map out the world 
in former geological periods, showing with confidence which 
areas have been beneath the sea and which remained dry 
land, with the difficulty that is experienced in getting any 
idea of what was the condition of the continents during the 
formation of the latest deposits, after man had penetrated 
into Europe, and all the species of animals and plants now 
living had come into existence. And yet, until we under- 
stand the youngest of the geological formations, it is almost 
idle to speculate on the more ancient conditions of the 
earth’s surface. Whilst, for instance, it is held by many 
that much of northern Europe and America was depressed 
below the level of the sea in post-tertiary times, and rose 
* Antiquity of Man, 4th edition, p. 372. 
