304 Dr. W. F. Sume — Notes on Russian Geology — 



probable. Under these circumstances tbe prime cause operating, 

 according to Sir H. Howorth, in the production of Loess and Bh.ck 

 Earth appears entirely inadequate. At the same time, Sir Henry is 

 to be thanked for the number of facts which he has brought together 

 after undoubtedly long and careful reading, though the interpretations 

 he has put upon them may frequently be open to much adverse 

 criticism. 



The second theory, that of Baron von Eichthofen, is set forth 

 clearly in the same volume as the above (pp. 293-305), and further 

 study of his views, there brought together in a small compass, only 

 serves to strengthen my belief in the great value of his contribution 

 to this subject. 



It is not necessary here to repeat how completely the vast majority 

 of the conclusions formulated by him with regard to the Loess have 

 been proved to be applicable to the sandy clay of S. Eussia. 

 Further, wherever we find unbroken land-shells, and remains of 

 a typical steppe fauna, there the presence of Loess will have, in 

 all probability, to be attributed to the action of wind. 



Baron von Eichthofen points out that there are two great classes 

 of places where the dust of continents will rest permanently, and 

 continue to accumulate through ages : 



" The first includes the central regions of continents, where the 

 water has no drainage towards the sea, but is collected in inland 

 basins, from whence it gradually disappears by evaporation," (For 

 further details see p. 298.) 



" The second comprises such regions as the prairies, savannas, 

 llanos, pampas, and steppes, where there is an alternation of a dry 

 and a rainy season. Where this occurs the amount of dust put 

 in motion and distributed through atmospheric agency can reach 

 enormous proportions." Such conditions are in a measure prevalent 

 in S. Eussia, where a very dry summer frequently succeeds the long 

 winter snows, and an autumnal rainy period follows the summer 

 droughts. 



As regards the original glacial origin of the Loess advocated by 

 me. Baron von Eichthofen fully agrees in regarding it as partly 

 resulting from glacial trituration. Indeed, he came to the conclusion 

 (" China," voL ii. p. 748) that the time of the deposition of the Loess 

 as a steppe formation in Central Asia coincides with the Glacial era 

 in Europe, and in Germany it appears to have been formed after 

 the first, and before (or during) the second glaciation. 



Practically, then, the differences between the views held by Baron 

 von Eichthofen, and those which I have been led to adopt, are 

 reduced to a minimum. Indeed, one cannot but be struck with the 

 keen appreciation of every point of importance shown by him in his 

 classical treatises. In my previous paper I failed to comprehend 

 how fully he had discussed the subject in its various bearings, and 

 desire here to tender an apology for my unwitting misrepresentation. 



Subsequent to the publication of my paper in the Geol. Mag. 

 December, 1892, Prof. Dokoutchaiefi" of St. Petersburg published 

 a note in the Bulletin Soc. Geol. Beige, January, 1893, on the Loess 



