248 THE POPULAR SCIENCE MONTHLY, 



of High Asia and the Tien Shan, whose streams have for ages trans- 

 ported the products of glacial attrition into Central Asia and North- 

 western China. Again, he insists that Richthofen has not given im- 

 portance enough to the parting planes, wrongly considered by his 

 predecessors in the study of Chinese geology as planes of stratifi- 

 cation. " These,'' he says, " account for the marginal layers of debris 

 brought down from the mountains. And the continuous and more 

 abundant growth of grasses at one plane would produce a modifica- 

 tion of the soil structurally and chemically, which superincumbent 

 accumulations could never efface. It should seem probable that we 

 have herein, also, the explanation of the calcareous concretions which 

 abound along these planes ; for the greater amount of carbonic acid 

 generated by the slow decay of this vegetation would, by forming a 

 bicarbonate, give to the lime the mobility necessary to produce the 

 concretions." 



It is hardly within the scope of this article to do more than present 

 in brief outline an exposition of the loess-theory that has made its 

 orginator already celebrated throughout Germany. Nor can we follow 

 Baron von Richthofen further into the extension of his postulate, where- 

 in one is scarcely surprised at finding a plausible and attractive appli- 

 cation of this idea of loess-formation to the entire Europe-Asiatic Con- 

 tinent, to the pampas of the South and prairies of the North American 

 world. While the three or four northwestern provinces of China 

 exhibit undoubtedly the strangest and most picturesque features of 

 this formation, its influence upon the climate of Central Asia, the 

 reactionary effect of this upon the surface configuration of the steppe- 

 lands, and thus on the historical and ethnographical development of 

 the cradle of the human race, are but some of the legitimate generali- 

 zations if not necessary results coming from this interesting phase 

 of nature. 



- 



THE NATURAL SETTING OF CRYSTALS. 



By J. B. CHOATE. 



THE study of natural history has of late years been largely directed 

 to the observation of laws according to which the development 

 of the individual species and genus takes place. Although the vital 

 principle which determines the growth and the nature of the animal 

 or plant eludes the search of shrewd and practiced observers, yet the 

 modes in which that principle manifests itself are in many cases pretty 

 well understood. In numberless instances we have been shown the 

 purpose with which Nature works on unceasingly toward certain defi- 

 nite anticipated ends. It is this fixed intent of Nature, rationally and 

 hopefully pursued, which reveals the thought of the universe. The 



