the rapids too numerous for the rivers to be navigable, except in
a few cases.
On the plateau of east Einmarken too, we have large rivers,
some of which have a more regular line of fall (Tana 180 miles,
basin 4000 sq. miles). ■
The country between the long erosion lines with the trough-
shaped cross section, between the fjords and the valleys, also bears
distinct marks of glaciers. The power of the ice to excavate where
the sub-stratum offers least resistance, and again to move upwards
over more compact strata, produces continually undulating section
lines, an endless alternation of heights and depressions, differing
decidedly from the surface-forms that are due to the ordinary
denudation by running water. This is most striking in the Wood-
land, where the beds of the granite, or the strike of the gneiss has
furnished good surfaces for the removal of boulders, so that there
is a constant alternation of polished knolls and pools of water or
bogs, as in Nordmarken. near Kristiania. Such is the structure
also over large portions of the Smaalenene and Akershus counties,
where the lakes amount to almost double the usual percentage of
the surface (about 4 %). On account of this structure, the forest
land is often exceedingly impracticable and difficult of penetration.
The Highland too is continually dotted with an infinity of lakes
and bogs.
Most of the larger lakes in Norway, however, are found in
the long valleys, generally arranged in distinct rows. The largest
of them, Mjosen (140 sq. miles, 60 miles long, 1500 feet in depth),
Bandsfjord, Spirillen, Kroderen, etc. generally lie at a height of
about 400 feet above the sea, just outside the border of the
Highland in the east country, and it is probable that it was
during the last glacial period when the land area was depressed
about 600 feet that the ends of the glaciers came out to the sea
by this line, and excavated these rock basins at the heads of the
fjords («lake period»), in exactly the same manner as they came
out during the great glacial period in the series of fjords on the
west coast («fjord period»). In the west country too, above the
head of the upper arms of the fjord, there is a corresponding
series of lakes at a height of less than 300 feet above the sea
e. g. Sandven, Eidfjord and Graven lakes in Hardanger, Breim,
Olden, Loen, Stryn, Hornindal lakes in Nordfjord (1594 feet in
depth). Here too there are rock basins of the typical form filled