PHYSIOGRAPHY OF NORTHWESTERN CHINA. 243 
Pumpelly wrote: 
That this deposit was formed in fresh water is shown by the presence of the shells 
found in the terrace of the Té-Hai. The uniform character of the loam in the different 
basins, and in all parts of the same basin, its great extent, and the fineness of the material 
of which it consists, are conditions which prove that it is not of local origin, or derived 
from the detritus of the neighboring shores, but that it was brought into the lakes by one 
or more large rivers, which must have drained an area of great extent. Now, throughout 
the region in question, the only rivers are those of the Yang-ho and Sankang-ho basin, 
and independently of the fact that these streams drain avery small area, the valley systems 
of these were almost entirely occupied by the lakes. Indeed, the only direction from which 
a river of importance could have come was from the west, in which case it could only have 
been the Huang-ho (Yellow river). Let us examine into the possibility of the existence 
of a communication of a valley of the Yellow river and the lake basins. 
The further discussion given by Pumpelly is an attempt to trace the 
possible changes in the river course, an attempt which, in the meager 
knowledge then available of the geography of China and of the physio- 
graphic processes by which streams may be diverted, is necessarily little 
more than suggestive, but which, nevertheless, indicates a bold grasp of 
some of the elements of the loess problem. Our own interpretation agrees 
with that of Pumpelly, in that we consider the formation under discussion 
to be a valley deposit, but differs from his in assigning to rivers the prin- 
cipal part in its extensive distribution. 
Von Richthofen, having observed the distribution of the loess more 
widely than Pumpelly was able to do, showed that the hypothesis of a 
lake formation was untenable on the ground that the loess occurs at such 
altitudes in the Wu-t’ai-shan and elsewhere in Shan-si, that no barrier 
could be conceived which might retain a body of water capable of accu- 
mulating the deposit. Pumpelly accepted this view.* 
Von Richthofen held that the mountains of China had gained the 
altitude which they now have before the loess was laid down. He says: 
We reach, in fact, the surprising result that the loess, in its vertical distribution, 
is independent of altitude above sea, and, with the exception of individual dividing moun- 
tain ranges, is found everywhere where a foundation for it occurs—provided that it has 
not been eroded or covered by alluvium. Now it can be proved that since the time of 
its formation there have been only slight relative changes of level in North China. In 
general at the time of its development, the surface forms of the region were nearly the 
same as now; the general elevation was, however, higher than at present, and the coast 
line was shoved farther out in the sea. The loess differs, therefore, from all other formations 
of like magnitude, in the remarkable fact that it was laid down in those relative altitudes 
* Relations of Secular Rock Disintegration to Loess, Glacial Drift, and Rock Basins. American 
Journal Science and Arts, vol. xvi, February, 1879. 
