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494 T. BELT ON THE STEPPES OF SIBERIA.
that west of the meridian of Samarova the blocks lie exposed
on the surface, whilst eastward they are completely covered by the
great deposit of clay; two thousand miles to the eastward of this
point, at Yakutsk, he states that the strata of the steppes con-
sist of loam, fine sand, and magnetic sand. In the deepest parts
twigs and leaves of trees are found

the alluvial plain of the Lena
also consists of similar deposits and the spoils of willow-banks.
" Everywhere," he says, " throughout these immense alluvial deposits
there are now lying the bones of antediluvian quadrupeds along
with vegetable remains." At Pavlodav I obtained teeth of the
Mammoth and Rhinoceros tichorinus from M. Hermann Paulson,
who had made a large collection of the bones of Mammalia from the
banks of the Irtisch. He told me they were exposed in sections of
the steppe-sands after freshets in the spring, when portions of the
banks were carried away

this information agrees with the position
of the mammalian remains assigned by the traveller Pallas, who
states that they do not occur in the marshes or low lands, but in
the precipices of the river-banks, in what I have called the steppe-
sands. It is interesting to find that they are found in the same
position as the Cyrena fluminalis. Further to the north, around the
coast of the Polar sea, within the Arctic circle, the carcasses of
mammoths have been found along with marine shells, proving, I
think, a small rise of the coast since they were deposited.
2. Theory of the Origin of the Steppes.
It is an interesting question, and one not easily answered, what
spread out these vast level sheets of sand and loam over the whole
northern base of Asia ? For weeks, as I was driven over them and
saw day after day the sun rise on a level horizon and set again on
the far-stretching plains, I puzzled myself with it. I ultimately
arrived at a solution which, I believe, meets all the requirements of
the case

and to obtain its acceptance by geologists, I think it will
be best to describe the steps by which I was led to it.
I soon saw that the plains had no relation to the present river-
system

the rivers simply cut through them

and there are no
defined river-basins, bounded by rocks of greater age, B in which they
might have been deposited. My next idea was that the sands must
be marine

and I find that this is the explanation of their formation
given by the celebrated geologist Prof. Bernhard von Cotta, who
visited the Altai in 1868. He states that the absence of the entire
series of rocks between the Permian and the Diluvial leads to the
conclusion that during the whole of this long period the region was
dry land, and that during the Diluvial period it was covered with
water up to the foot of the mountains. He says " at this time an
ocean, extending from the' Glacial Sea to the Ural, the Altai and the
Caspian and Black Seas, seems to have been a boundary between
Europe and the south and east of Asia. The absence of traces of
glaciers, and, indeed, generally of any vestiges of a glacial period,
such as are so frequently observed in Europe, may be accounted