Frof. Baron F. Richthofen—On the Origin of the Loess. 295 



arguments against it would, at least in part, be well founded ; but I 

 consider it not improbable that he would not have started the con- 

 troversy if he had taken the trouble to make himself acquainted 

 with the subject against which it is directed. 



Will you allow me, therefore, to offer to the readers of Mr, 

 Ho worth's article a short explanation of the views at which I arrived 

 regarding the mode of origin of the Loess when I was gazing daily 

 at its astounding deposits and grotesque features in the Chinese 

 provinces of Honan and Shansi, views which I found not only 

 corroborated during my further travels throughout all Northern 

 China and in the Mongolian Steppes, but which, on the strength of 

 comparative study, I was afterwards able to apply with equal force 

 to Tibet, the region of Khotan and Yarkand, and great portions of 

 south-western Asia, as well as to all Loess-covered regions of 

 Europe, and of the continents of North and South America. 



Any theory which undertakes to deal with the problem of the 

 origin of the Loess must give a valid explanation of the following 

 characteristic peculiarities of it, viz. : 



1st. The petrographical, stratigraphical, and faunistic diiference of 

 the Loess from all accumulations of inorganic matter which have 

 been deposited previously and subsequently to its formation, and are 

 preserved to this day. 



2nd. The nearly perfect homogeneousness of composition and 

 structure, which the Loess preserves throughout all the regions in 

 which it is found on the continents of Europe and Asia ; it offers 

 in this respect a remarkable contrast to all sediments proved to be 

 deposited from water within the last geological epochs, excepting 

 those of the deep sea, which are here out of the question. 



3rd, The independence of the distribution of the Loess from the 

 amount of altitude above sea-level. In China it ranges from a few 

 feet to about 8000 feet above the sea,^ and farther west it rises 

 probably to much greater altitudes. In Europe it is known at all 

 elevations up to about 5000 feet, at which it occurs in the Carpathians. 



4th. The peculiar shape of every large body of Loess, as it is 

 recognized where erosion has cut gorges through it down to the 

 underlying ground without obliterating the original features of the 

 deposit. These are different according to the hilly or level character 

 of the subjacent ground. In hilly regions the Loess, if little 

 developed, fills up depressions between every pair of lower ridges, 

 and in each of them presents a concave surface ; but where it attains 

 greater thickness, it spreads over the lower hills, and conceals the 

 inequalities of the ground. Its concave surface extends then over 

 the entire area separating two higher ranges, in such a manner as 

 to make the line of profile resemble the curve that would be 

 produced by a rope stretched loosely between the two ranges. 



1 I met with it in China, in 1870, only at an altitude of 6000 feet, and this 

 figure is given by Mr. Howorth (p. 76) erroneously as an observation of Mr. 

 Kiugsmill ; in 1871 I found thick deposits of Loess at an elevation of 7000 feet in 

 Southern Mongolia, and of 8000 feet on the Wu-tai-shan range in the province of 

 Shansi. 



