Page:Popular Science Monthly Volume 24.djvu/260

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248
THE POPULAR SCIENCE MONTHLY.

of High Asia and the Tien Shan, whose streams have for ages transported the products of glacial attrition into Central Asia and North-western China. Again, he insists that Richthofen has not given importance enough to the parting planes, wrongly considered by his predecessors in the study of Chinese geology as planes of stratification. "These," he says, "account for the marginal layers of débris brought down from the mountains. And the continuous and more abundant growth of grasses at one plane would produce a modification 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 originator 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 application of this idea of loess-formation to the entire Europe-Asiatic Continent, 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 generalizations—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 definite anticipated ends. It is this fixed intent of Nature, rationally and hopefully pursued, which reveals the thought of the universe. The