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CLIMATE OF JAPAN. 887
the name of Kuro-sivo, or " Black Stream," corresponds
in its course and climatic
influences with the Gulf Stream of the North Atlantic. It flows close by the east
side of the large islands, and its tepid waters, coming from the Straits of Malaysia
and the Philippines, bring with them an atmospheric current far milder than that
of the neighbouring mainland. Its mean temperature, some four or five degrees
lower than that of the Gulf Stream, varies from 74 to 81 Fahr., and thus exceeds
by about nine degrees the normal temperature of the marine waters under the same
latitudes. During the south-west summer monsoons, the stream flows directly to
the coasts of Kiu-siu and Sikok, and the south side of Hondo ;
while in winter it is
diverted by the polar winds towards the north-east. Its velocity varies from about
30 to 45 miles a day, and the plummet has recorded depths of 3,000 feet and
upwards.
In the north the Oya-sivo polar current, emerging from the Sea of Okhotsk,
meets the Kuro-sivo, one branch of which penetrates through Tsugar Strait. As
in the Atlantic, the two streams move side by side in parallel lines, but in opposite
directions, under a sky frequently charged with dense vapours. The Oya-sivo, which
in winter fringes the east coast of Yeso with drift ice, also brings large quantities
of marine animals from the northern latitudes, thus contributing abundant supplies
of food to the inhabitants of Nip-pon. The coasts of Yeso, which are exposed to
the two streams of the North Pacific, correspond in this respect to the banks of
Newfoundland.
West of the Japanese Archipelago, a branch of the Kuro-sivo flowing round
the island of Tsu-sima also contributes to raise the normal temperature in these
latitudes. Its influence is chiefly felt on the north side of Hondo, where its waters
have an average temperature of about 69 Fahr. But the Tsu-sima stream, as it
has been named by Schrenck, does not flow constantly in the direction from south
to north. Under the action of the polar winds it is deflected in winter towards the
south at least on the surface, and it then sweeps round between the Lu-chu Islands
eastwards to the Kuro-sivo. But, owing to its small volume, its influence even in
summer is of secondary importance in determining the oscillations of the tempera-
ture. Between the two slopes of the Japanese Archipelago the contrast in this
respect is most striking. Here the isothermals traced from west to east are far
from, coinciding with the parallels of latitude. The mean temperature at equal
distances from the equator is much higher on the east than on the west side, where
the mountains of like elevation remain snow-clad for a considerably longer period
of the year. Pending more numerous and accurate meteorological observations,
it may be stated in a general way that the isothermals are deflected more and more
towards the north as we approach the Arctic zone. Thus, while the difference
between Smith Japan and the corresponding coast of China is scarcely more than
'! Fahr.,
it exceeds H Fahr. between Yeso and Russian Manchuria. Thanks also
to the moderating effects of the Pacific throughout the year, the periods of extreme
cold and heat are delayed till February and August respectively. September is
normally a warmer month even than July.
* "Unbeaten Tracks," i., p. 212. t A. H. Kcane's "Asia," p. 612.