vered and exposed to the action
of the atmosphere, while farther down it may yield very good coal.
It is probable besides that the layers of shale, which often
surround the coal seams, have in this case been mistaken for the
true coal. For those who are inexperienced in coal-mining to make
such a mistake is the rule and not the exception. ]

[Footnote 209: In order not to write without due examination about
figures which have been written about a thousand times before, I
have, with the help of Petermann's map of North and Middle Asia in
Stieler's Hand-Atlas, calculated the extent of the areas of the
Siberian rivers, and found them to be:--

Square Geographical
kilometres. square miles.
River area of the Ob (with the Tas) 3,445,000 62,560
River area of the Yenisej 2,712,000 49,250
River area of the Lena 2,395,000 43,500

Of these areas 4,966,000 square kilometres, or about 90,000
geographical square miles, lie south of 60 deg. N.L. ]

[Footnote 210: For the northern hemisphere it is the general rule
that where rivers flow through loose, earthy strata in a direction
deviating considerably from that of the parallels of latitude, the
right bank, when one stands facing the mouth of the river, is high,
and the left low. The cause of this is the globular form of the
earth and its rotation, which gives rivers flowing north a tendency
towards the east, and to rivers flowing south a tendency to the west
This tendency is resisted by the bank, but it is gradually eaten
into and washed away by degrees, so that the river bed, in the
course of thousands of years, is shifted in the direction indicated. ]

[Footnote 211: As specimens of the sub-fossil mollusc fauna of the
_tundra_ some of the common species are delineated on the opposite
page. These are:--1. _Mya arenaria_, Lin. 2/3 of natural size. 2.
_Mya truncata_, Lin. var. _Uddevallensis_, Forbes. 2/3 3. _Saxicava
pholadis_, Lin. 2/3. 4. _Tellina lata_, Gmel. 2/3 5. _Cardium
ciliatum_, Fabr. 2/3. 6. _Leda pernula_, Muell. var. _buccata_,
Steenstr. Natural size. 7. _Nucula expansa_, Reeve. Nat. size. 8.
_Fusus Kroyeri_, Moell. 2/3. 9. _Fusus fornicatus_, Reeve. 1/2. 10.
_Fusus tornatus_, Gould. 2/3. 11. _Margarita elegantissima_, Bean.
Natural size. 12. _Pleurotoma plicifera_, Wood. Natural size. 13.
_Pleurotoma pyramidalis_, Stroem. 1-1/2. 14. _Trichotropis