(1) Huang-t'w referring to all deposits, whether Aeolian or fluvial. 
(2) Loess, the pure zolian or sub-aerial deposit. 
(3) Shao-t'u, that substance, which resembles Loess, but contains a certain 
proportion of clay. 
The last usually contains more carbonate of lime than the second,* and 
generally occurs at the bottom of the deep ravines in the Huang-t'u formations. 
So far as I have been able to gather, the lime nodules mentioned by various 
writers occur in the Shao-t’u. The origin of the latter is difficult to determine, t 
but it is believed by some to be the result of decomposed Felspathic rock. 
For want of any other name, I call the sedimentary beds of Shensi “the 
Shensi formation,” but the exact relationship between this and the Shansi 
formation I cannot define, though it certainly resembles the formation between 
Chiao-ch’éng Shan and the Huang Ho. 
The country in the immediate vicinity of T’ai-yiian Fu, our starting- 
point, has been investigated by the members of the Carnegie Expedition, so 
that I will commence drawing on my note book at the western bank of the 
Fén Ho. In the preparation of this Chapter I have had frequent recourse to 
“Research in China”; the line of march followed by the authors of that 
work was from Pao-ting Fu in Chihli westward to Wu-t’ai Shan in Shansi; 
thence southward through the middle of Shansi as far as T’ung-kuan Hsien, 
just beyond its south-western border; and from this point westward again in 
exploration of the Ch’in-ling range and the country south of the Wei Ho in 
Shensi. 
After continuing westward from T’ai-yiian Fu, in Shansi, to Yii-lin Fu, in 
Northern Shensi, our own route lay in a direction roughly parallel to that of 
the Carnegie Expedition, extending as it did from North to South down the 
middle of Shensi. The Carnegie Expedition did not enter Kansu at all, and 
the country we traversed seems to have been visited by no geologist. We 
thus had the opportunity of seeing a mountainous country, namely the Chiao- 
ch’éng Shan, dividing the Fén Ho from the Yellow River, the existence of 
which seems to have been unsuspected by Richthofen, and only guessed at by 
the members of the Carnegie Expedition. Both parties apparently confined 
themselves to the valley of the Fén Ho, and formed their opinions of what 
lay to the westward from what they saw of the small range of mountains 
forming the north-western boundary of that valley. 
Richthofen speaks of the country between the Fén Ho and the Yellow 
* The loess has a large proportion of clay, but disseminated and not separated as appears to be the case with the Shao-t's. 
t The CaO, CO, of the calcareous nodules is probably derived from the upper beds by water action, 
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