THE LOESS-DEPOSITS OF NORTHERN CHINA. 245 



some others, of its stratification, and from this a proof of its origin as 

 a marine deposit. 



But, since attention was first directed to this formation by Mr. 

 Pumpelly, in 1864, its structure has been more carefully examined by 

 other geologists, whose hypotheses are pretty generally discarded for 

 that of Baron von Richthofen. This gentleman, who may be consid- 

 ered facile princeps among foreign geologists who have visited China, 

 argues that these apparent layers of loess are due to external condi- 

 tions, as of rocks and debris sliding from surrounding hill-sides upon 

 the loess-dust as it sifted into the basin or valley, thus interrupting the 

 homogeneity of the gradually rising deposit. In the sides of gorges 

 near the mountains are seen layers of coarse debris which, in going 

 toward the valley-bottom, become finer, while the layers themselves 

 are thinner and separated by an increasing vertical distance ; along 

 these rubble-beds are numerous calcareous concretions which stand 

 upright. These are, then, the terrace-forming layers which, by their 

 resistance to the action of water, cause the broken chasms and step- 

 like contour of the loess regions. Each bank does, indeed, cleave ver- 

 tically, sometimes since the erosion works from below leaving an 

 overhanging bank ; but, meeting with this horizontal layer of marl- 

 stones, the abrasion is interrupted, and a ledge is made. Falling clods 

 upon such spaces are gradually spread over their surfaces by natural 

 action, converting them into rich fields. When seen from a height in 

 good seasons, these systems of terraces present an endless succession 

 of green fields and growing crops ; viewed from the deep cut of some 

 stream or road-bed, the traveler sees nothing but yellow walls of loam 

 and dusty tiers of loess-ridges. As may be readily imagined, a coun- 

 try of this nature exhibits many landscapes of unrivaled picturesque- 

 ness, especially when lofty crags, which some variation in the water- 

 course has left as giant guardsmen of fertile river-valleys, stand out 

 in bold relief against the green background of neighboring hills and a 

 fruitful alluvial bottom, or when an opening of some ascending pass 

 allows the eye to range over leagues of sharp-cut ridges and teeming 

 crops, the work of the careful cultivator. 



The extreme ease with which loess is cut away tends at times to se- 

 riously embarrass traffic. Dust made by the cart-wheels on a highway 

 is taken up by strong winds during the dry season and blown over the 

 surrounding lands, much after the manner in which it was origioally 

 deposited here. This action, continued over centuries, and assisted by 

 occasional deluges of rain, which find a ready channel in the road-bed, 

 has ^hollowed the country routes into depressions of often fifty or a 

 hundred feet, where the passenger may ride for miles without obtain- 

 ing a glimpse of field or landscape. Lieutenant Kreitner, of the 

 Szechenyi exploring expedition (whose pleasant article on Thibet ap- 

 peared in " The Popular Science Monthly " for August, 1882) illus- 

 trates, by a personal experience when in Shansi, the difficulty and dan- 



