Full resolution (JPEG) - On this page / på denna sida - XVII. The Amúr district and the Amúr railway
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THROUGH SIBERIA
in height. The embankments are built of stone and
gravel from the cuttings. This is an imposing piece of
engineering.
Friday, October 10. A little farther west there is
a smaller tunnel, called the "little tunnel," only about
300 yards long, through another ridge, near the station
of Obluche. This also goes through porphyrite, but of a
somewhat harder, more quartziferous kind than the last.
This tunnel is remarkable for the fact that the mountain
is everywhere frozen to a depth of more than 250 feet
below the surface. The temperature within the mountain
has risen since the opening of the tunnel. The first
winter it was found to be —8° C. (17’6°F.) a few yards
below the surface ; it has been constantly rising since
then. We now found -o*3° C. (31*5° F.) in a side level,
about 130 feet below the surface, and at a depth of about
200 feet it was something like - o*l° C. (31*8° F.). Such
conditions of temperature are not found anywhere else
about here ; as a rule the soil is not perpetually frozen
in this district, and in winter the frost only extends about
6 feet into the ground. The low temperature in this
tunnel must be due to the disintegration of the rock ;
it is split through, sometimes with great open crevices,
to depths greater than those which are reached by the
tunnel. Refrigeration must take place in the following
way : the cold, heavy air sinks through these crevices
in winter, cooling the rock to low temperatures, and the
water that has penetrated into the crevices freezes ;
while, on the other hand, the warming of the surface
by the sun’s rays in summer penetrates very slowly,
and the warm air that is then formed in the uppermost
part of the crevices cannot sink, as it is so light, so that
the heavy, cold winter air remains throughout the summer
in the depths, in any case to a great extent, where there
is no draught. In this way a sort of ice-cellar is formed
394
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