713 
also plentifully on the Kama and around Ufa; and on the Asiatic 
side of the Ural mountain it occupies an extensive district near 
Kamensk, in lat. 56°, and another between Miask and Sviask. Its 
northern and southern limits in Siberia were not ascertained, but it 
was found in the Baschir country on both flanks of the southern 
Ural, and in the steppes of the Kirghis, Between Orenburg and 
the mouth of the Volga it is wanting, the surface of the district 
consisting of marine detritus, containing shells of species which 
now exist in the Caspian: it appears to be equally wanting south 
of Tzaritzin on the Volga (lat. 48° 40’), as well as in the steppes of 
the Kalmucks, occurring in only very limited patches along the Sea 
of Azof, or south of the granitic steppes. It abounds, however, to 
the north of that steppe, over a vast area, in broad valleys, on slopes 
and plateaux, and at all levels to the height of 400 feet ; also on rocks 
of all ages, even overlapping the southern skirts of the great north- 
ern drift. It invariably constitutes the surface-soil, and is composed 
of black particles mixed with grains of sand, the former being so 
fine as to rise into the air even under the pressure of a horse’s feet 
on the turf which covers it. 
One of the marked features of all the alluvia of Russia charac- 
terises also the Tchornoi Zem. Wherever it occurs on plateaux or 
slopes, it is cut into by the ravines, called ‘ avrachs” or “ baltas,” 
produced in the first instance by fissures formed during droughts, 
and widened as well as deepened subsequently by debacles arising 
from the melting of the thick falls of snow. 
This black earth constitutes the finest soil in Russia, both for 
grass and wheat, and after yielding many crops in succession, it re- 
quires only a year or two of fallow to regain its fertility ; the pea- 
sants, moreover, have prejudices against the use of manures, and Mr. 
Murchison believes that these feelings are strengthened by the na- 
tural productiveness of the soil. 
2. Chemical Composition.—Ananalysis of aportion of the Tchornoi 
Zem, made by Mr. R. Phillips, Chemist to the Museum of Economic 
Geology, yielded in 100 parts, 69:8 silica, 13°5 alumina, 1:6 lime, 
7- oxide of iron, 6:4 vegetable matter, and traces of humic acid, 
sulphuric and chlorine*. The black earth does not therefore differ, 
. * Since the paper was read the author has been favoured with an ana- 
lysis by M. Payen, the celebrated French agricultural chemist. The follow- 
ing statement is a translation of part of M. Payen’s communication :— 
Tatants 6°95 combustible organic matter. Alumina... 9°04 
£ ah jo incombustible f Soluble in Oxide of iron 5°62 
Pst oit matter. boiling hy- L y3.75 Lime ..... 0°82 
drochloric Magnesia . 0°98 
acid. Alkaline } 1:21 
Chlorides 
Insoluble Silica... 71°56 
Feed ra staat) pack 
tic acid. Magnesia. 0°24 
The combustible organic matter indicated the presence, in 100 parts of the 
original earth, of water 4°81, azote 2°45, or together 7°26. The volume of 
the azote, M. Payen states, is remarkable. 
