The Geographical Journal (Journal of the Royal Geographical Society): Volume IX, No. 4 [‎219v] (109/172)

426
THE RIVER ODER.
Where a river is concerned, the occurrence and duration of frost
is naturally of special importance, and the comparison of Breslau and
Stettin gives interesting results. On a mean of forty winters, Irosts of
less than ten days’ duration occur with almost equal frequency, hut
for longer periods Breslau is higher, continuous frosts of over a month
occurring there twice as often as at Stettin. Nevertheless, the longest
frost on record (December 17, 1870, to February 16, 1871) lasted exactly
the same time at both places. The lustral averages of nine stations for
the forty years 1851-90 show temperatures below the general mean
from 1851-55 to 1861-65, above it from 1866-70 to 1881-85, and again
below it from 1886-90.
The geological work was placed in the hands of Dr. Dathe, who is
responsible for the hill and mountain districts, and of Prof. Dr. Wahn-
schaflfe, who surveyed the low-lying plains, the two regions being
practically separated by the contour-line of 650 feet (200 metres). No
part of the Oder basin rises above the snow-line, so the term “ mountain
region ” is used in the same sense as in the geography of this country,
and includes everything more than 1700 to 2000 feet above sea-level,,
leaving the 600 to 1700 feet belt as “hill country.” For geological
purposes, the two arrange themselves into (1) the Sudetic mountains,,
and (2) their subsidiary ranges, (3) the Beskids, and (4) the Upper
Silesian plateau; but the Sudetic mountains are understood to extend
only from the Lausitzen Pforte to the Miihrische Pforte, and to include
the Eiesengebirge, Eulengebirge, and Altvater groups, characterized
by a bed of crystalline schist, which, although the oldest formation
here, overlies most of the more recent strata. Special interest attaches
to the northern diluvium, which here, as elsewhere in North Germany,,
occurs up to about 1600 feet above sea-level. The distribution of this-
deposit has been found to extend over a much wider area in the Sudetic
range than was supposed, a point of much importance on account of the
different permeability of the soil, and consequent change in the amount
of drainage which may be expected to find its way to the various feeding
streams.
dhe low plains of the Oder basin are almost entirely covered with
quaternary deposits, but here and there these are so thin that the
tertiary strata have become exposed, and the river itself has of course-
made a number ot sections. The tertiary rocks appear most frequently
m the neighbourhood of Brieg, to the north of Breslau, south of Liegnitz,
and round Posen, but especially in the basin of the Warthe, and they
consist chiefly of middle and upper Oligocene and Miocene beds. The
quaternary deposits are the diluvium and the alluvium, the former the
work of the Eusso-Scandinavian ice-sheet, which is now known to have
overspread North Germany twice, with an inter-glacial period inter
polated, and the latter the result of agencies at work since the total
disappearance of the ice-sheet.