December 1, 1897.] 



KNOWLEDGE. 



283 



lands, have softened the former contours of the country ; 

 at present they are rapidly becoming eroded, producing 

 locally a series of ravines." 



Away across the great Siberian steppes, and into the 

 heart of China,* where the continental uniformity has 

 impressed itself on the character of a people, the decay of 

 the older structural features is levelling up the country, 

 and is producing, here a cultivated plain, here a mere 

 desert of shifting sand-dunes. Whether the winds or the 

 rivers are engaged in distributing the material, the result 

 is inevitably the same. The heart of our continent is 

 becoming shorn of all its salient features, and the form 



stones of comparatively recent age.* These are now 

 laid hold of by the wind, and furnish material for the 

 sand-blast that attacks all the projecting masses in the 

 country. The bluffs of older rock that still survive are 

 being eaten into and deeply scored by the denuding wind ; 

 while the great range between the temperature of day 

 and night assists in the destruction of their surfaces, by 

 alternate expansions and contractions. The result is that 

 the desert is filling up, and is overflowing into Egypt at 

 its eastern end. The deposits consist in this case, as M. 

 Holland says, of " ae-rial alluvium, the formation of which 

 is contemporaneous and is going on beneath our eyes."! 



Fig. 1. — Slope of the Scbwarzliorn, summit of the Fliiela Pass, Switzerkncl, showing biir::il of original features in 

 cones of fletritus. (From a pliotograph by Sigrist-Herder. Davos-Platz ) 



of its surface is approximating towards that of the 

 primfEval earth. 



The burial of normal landscapes under the action of 

 the wind is well exemplified in the Sahara. Prof. Walther 

 believes that granites have contributed the sands of this 

 great desert, while Zittel points to the sandstones of 

 Devonian age that fringe the area on the south. ' In 

 any case, the present dry conditions were probably pre- 

 ceded by far wetter ones, under which huge fans of 

 alluvium were formed, providing a series of loose sand- 



We can here only refer to the " Loss " of Centra 

 Europe, covering much of the country from the Rhine to 

 the East of Russia— a fine clayey deposit, brought down 

 by flooded streams and spread out uniformly by the wind ; 

 to the enormous stretches of modern river-gravel in the 

 valley of the Garonne or of the RhAne ; and to the Alpine 

 debris poured out into Bavaria (Fig. 3), or into Italy, from 

 Turin to the Adriatic. In every continent, from the 

 basin of Australia to the plateaux of the United States, 

 from the feet of the Central Asian ranges to the I63s-filled 



* See Ton Eichthofen, " China," £d. I., p. 56, et<;. 

 t See Sakolow, "DieDiinen," 189i, p. 195. 



* G. KoUand, "Sur les grandes Dunes de sable du Sahara," Bull. 

 Sot: giol. de France, Ser. 3, Tome X. (1881-2), p. 38. 

 t Op. ciL, p. 35. 



