242 RESEARCH IN CHINA. 
narrow one within exact limits. It is a broad one, sufficing to place in 
true relative sequence a stage of development reached by different areas 
in different degrees within longer or shorter time, but a stage reached by 
all essentially contemporaneously within the limits we can now set for the 
beginning and end of the epoch. 
The T’ang-hién epoch began with an elevation, which resulted in 
general dissection of the still older and more aged features of the Pei-t’ai 
surface. It ended with the initiation of those changes of level and climate 
which occasioned the deposition of the Huang-t’u formation; that is, when 
the degradation in the region under discussion gave place to aggradation. 
And with the close of the T’ang-hién stage began the Hin-chéu stage. 
4 
HIN-CHOU STAGE. 
The Hin-chéu stage differs from the two preceding ones in being 
an epoch of aggradation within the provinces of Chi-li and Shan-si. The 
principal fact was the accumulation of the earlier deposits of the Huang-t’u 
formation. We must distinguish the stage of earlier deposits, at least 
theoretically, in classification, because the Huang-t’u has been forming 
since the beginning of the Hin-chéu epoch and is forming now. ‘Therefore 
the Huang-t’u period covers all the time since that beginning, but the 
Hin-chéu epoch does not. It was closed by warping, to which the major 
orographic features of northern China are due, and that warping initiated 
the latest epoch, which we call the Fon-ho. The Huang-t’u period is, 
therefore, equal to and coincident in time with the Hin-chéu and Foén-ho 
epochs together. 
The accumulation of the Huang-t’u formation can be discussed only 
as a phase of the loess problem of China, a problem which has been involved 
in much misconception because the physiographic conditions of the Hin- 
chéu stage were not understood, and because the characteristics of the 
Huang-t’u formation present difficult questions for solution. If the inter- 
pretation of the physiographic history, which leads to the recognition of the 
Hin-chéu stage of mature topography, be correct, we have gained a point 
of view from which to discuss the unusual character of the Huang-t’u. Let 
us glance at the earlier conceptions of its development. 
Earlier theories of Chinese loess —Pumpelly described the loess or 
Huang-t’u formation as a lake or terrace deposit.* He attributed the 
formations of the lake basins to the dislocation of the plateau of North 
China, and traced a former connection between the valleys in which he 
observed the loess and the present course of the Yellow river. 

* Smithsonian Contributions to Knowledge, vol. xv, pp. 39-45. 
