8 o The Loess of the Rhine and the Danube . [January, 
the level of the river, and Dr. Sandberger informed me that 
it goes down to at least 50 feet below it. Here, then, the 
valley must have been excavated below its present depth to 
allow of the deposition of the gravel which preceded that of 
the loess. Near Basel, as I have shown in Fig. 1, the older 
gravel rests directly against the steep slopes of the rocks 
bounding the valley, proving again that the latter had been 
excavated long before the deposition of the loess commenced. 
At Mosbach the gravels, containing an older fauna than that 
of the loess, though above the level of the river, are yet 
several hundred feet below the altitude the loess attains to, 
and that the latter has all been deposited since, is proved by 
it everywhere containing a younger fauna. The Mosbach 
gravels belong to the time of Rhinoceros etruscus , the loess to 
that of R. tichorinus. 
These faCts are very strongly in favour of the pre-diluvial 
origin of the great valleys, and there are others still more diffi- 
cult to explain on any other theory. As already mentioned, the 
loess extends far up the flanks of the recent volcanic cones of 
the Lower Eifel, and at Mahlsberg attains an elevation of 600 
feet above the Rhine. The most ardent advocate of the 
theory that the loess has been left by the river whilst it ran at 
higher levels will not, I think, suggest that the volcanic 
cones have been carved out by it, and yet excepting on that 
supposition their theory falls to the ground. Another most 
serious objection to it is that it requires that the whole of 
the great valleys of the Danube and the Rhine have been 
excavated in one comparatively short period, namely, that 
of the mammoth and woolly rhinoceros. The upholders of 
the theory may say — “ Not excavated, but re-excavated 
through the gravels and clays that were deposited in them 
in Miocene times but the loess extends far higher up the 
sides of the valleys than we have any evidence that the 
Miocene deposits ever reached to. 
In the whole of the long Pliocene period it would appear 
that the land was above the level of the ocean, and we are 
to suppose, on the theory against which I am contending, 
that the rivers did not then wear down their channels, but 
waited for the mammoth period before they commenced 
doing so. Both in the valleys of the Danube and the Rhine 
the Pliocene epoch is unrepresented by fossil remains. I 
asked Prof. Suess what was the meaning of this great 
hiatus ? and he replied that during Pliocene times the rivers 
were re-excavating their channels through the Miocene ac- 
cumulations, and that periods of destruction are not periods 
of deposition in the same areas. At first, the new river 
