THE GLACIAL PERIOD. 245 



" wind-stream deltas " which extend as lofty sand-ranges from 

 each pass in the mountains eastward far out on the desert. 1 If 

 we except the dunes of our coast-regions, the only considerable 

 areas of wind-driven sand which occur in Europe are those of 

 Olkucz, Schiewier, and Ozenstockau in Poland, around which 

 stretches a seemingly boundless wilderness of shifting sand. 

 During storms this sandy plain appears like a tumbling and 

 rolling sea, the sand-hills rising and dipping like the waves of 

 the ocean. 2 These sands are part of the Northern Drift, and 

 were deposited by the flood-waters descending from the mer de 

 glace at the time of its retreat. Occasionally, also, in the 

 Eussian Steppes patches of drifting sand appear, and doubtless 

 there are many other sandy tracts in Europe which might drift 

 under the action of the wind were they not fixed by vegetation. 

 But these expanses of sand have not been transported by wind 

 from one part of the Continent to another. Most of them are 

 flood-deposits of the Glacial Period, while others represent the 

 lake-bottoms and sea-beds of Tertiary times. They are, in short, 

 proofs rather of former humidity than aridity. 



2. The geographical distribution of the loss is incomprehen- 

 sible on the supposition that it owes its accumulation to the 

 action of wind. Why should it occur so commonly in the 

 valleys, and die off upon the plateaux ? And why, as Dr. 

 Jentzsch has asked, 3 should it be wanting in the Erzgebirge, the 

 Thuringerwald, and other hilly districts of Middle Germany, 

 while the regions on either side are more or less thickly covered 

 with it ? The same geologist refers to the occurrence of that 

 narrow zone of loss which fringes the southern borders of the 

 Northern Drift in Northern Germany, and in places attains 

 a considerable thickness ; and he asks how it is possible to 

 believe that dust-storms could have worked only within that 

 narrow zone. In point of fact the distribution of loss in Europe 

 bears no relation whatever to the track of prevalent winds. On 



1 Arner. Jour, of Science and Arts, vol. xvii. (1879), p. 139. 



2 Naumann's Geognosie, Bd. ii. p. 1173. 



3 Verh. der k.-k. geol. Reichs. (1877), Bd. xxvii. p. 254. 



