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ORIGIN OF THE GRITS OF KALTCHEDANSK. 
Tertiary Millstones of Kaltchedansk . — Having satisfied ourselves of the existence 
in this part of Siberia of a palaeozoic succession from a metamorphic axis, which 
had been broken up by porphyry and other intrusive rocks, we next wished to 
ascertain the nature of a deposit, which we had heard of as yielding the finest mill- 
stones of the region, and also some traces of coaly matter. We accordingly re- 
embarked and descended the Issetz to the village of Volchof, where the river begins 
to quit the plateaux and wander in the wide plains of Siberia. 
From Bayanova to Volchof (the village represented in the lithograph facing 
p. 358), the cliffs are essentially composed of porphyry, which occurs both in 
vertical and laminated masses, and also in bosses which peer out irregularly at 
intervals, the former conveying to us the idea of having, like the schaalstein, 
been formed contemporaneously with the palajozoic rocks, the others being of 
the age of the greenstones and porphyries which have thrown up the Ural chain. 
The hills of Krasnoi-gora on the left bank of the stream, about 150 feet high, 
offered us a clear section of the porphyries, and also of the millstone grit of which we 
were in search, and at once taught the origin, age and structure of all the strata 
which cover the adjacent plateau of Kaltchedansk ; as shown in this woodcut. 
52 . 
Grit and clay with brown coal. 
These grits are, in fact, part of what we believe may prove to be wide-spread ter- 
tiary accumulations in Siberia, and they owe their peculiar character to having been 
derived from the quartzose, porphyritic and other intrusive rocks on which they 
rest, and out of whose materials they have been entirely composed. Thus, some of 
these courses consist of white and greyish clays, arising from the decomposed 
felspar — often by no means a bad potter’s clay, in which leaves and remains of 
wood have occasionally been transmuted into a poor brown coal, with which small 
portions of amber are here and there associated. 
The grits which occupy the highest part, range from the banks of the Issetz into 
an arid plateau, and to the north side of the high road to Tobolsk, are cut into 
by a number of shallow pits (twenty to thirty feet deep), the beds being everywhere 
perfectly horizontal. The extracted blocks of millstone cover the surface for 
