308 Dr. W. F. Hume — Notes on Russian Geology — 



have noticed it not only in the Jitomir district, about a hundred 

 miles to the W. of Kieff, but also in passing from Eussia into 

 Austrian Poland. The last locality at which it was actually 

 observed by me was Jaroslavl, a town situated on the railway 

 between Cracow and the old city of Premysl. Beyond that point 

 Loess alone seemed to be the prevalent surface deposit. The first 

 point of importance is the close connection existing between the 

 Loess and the Black Earth. Murchison included both deposits 

 under the common term Tchernozem ; but this latter, in the truest 

 sense of the term, should be restricted to the upper strata, rich in 

 humus contents. Schmidt regards it as practically identical with 

 Loess (Zeits. Deutsch. Geol. Ges. vol. xxix. p. 830-31). Eichthofen 

 spates : " The black colour, which is proper to the uppermost layer 

 only, appears to result solely from the formation of vegetable mould, 

 the deeper portions showing the brown colour of the Loess, together 

 with its structure, although this appears to be less perfect than in 

 the former case." Personal observation has left no shadow of a 

 doubt on my mind as to the intimate connection between these two 

 types of deposit. Eeference has already been made as to the gradual 

 passage from pure Loess to Black Earth observed in a ravine at 

 Kharkov, and an example of the interlamination of the two at their 

 point of junction has been cited from Bielgorod. 



But these cases, developed on a small scale at the above localities, 

 may attain much greater proportions. Eepeatedly the dark brown 

 humus-bearing bed forms distinct lenticular patches (often 3 or 4 feet 

 in thickness at the centre and extending some little distance in a 

 horizontal direction) running through the yellow clay. 



The further and final stage is attained when the Black Earth 

 forms a distinctly marked stratum, actually overlain by a true Loess. 

 This is beautifully observed in the ravine near the railway station 

 at Kieff, where a thick layer of Black Earth is overlain by some 

 seven feet of Loess. 



But the inter-relationships of the two deposits are still further 

 brought out if a closer examination be made of the materials 

 composing them. Not only does Black Earth agree with Loess in 

 its superficial position, its existence at most varying level, its 

 occasionally purely local development, but it possesses the same 

 want of consistency when rubbed in the fingers. The chemical 

 composition is in most respects similar. Thus Loess may be said 

 to be composed of pure silica in the form of sand-grains, clays, 

 calcareous constituents (as concretions frequently), and oxide of 

 iron, acting as a colouring material. Compare with this the analysis 

 of Black Earth made by Mr. H. Phillips for Murchison's work : 



Silica 



Alumina 



Lime 



Oxide of Iron 



Organic Matter 



Traces of Organic Matter H2SO4, CI., etc. 



69-8 

 13-5 

 1-6 

 0-7 

 6-4 

 1-7 



