CLIMATIC LIMITS OF CULTIVATED PLANTS 2%
of others having more bearing on the production and distribution of
mercantile commodities, it may be mentioned that the northern limits
of various cultivated plants whose range is somewhat rigorously deter-
mined by climate, such as the orange (284) and the vine (291), are
higher in Europe than in the west of North America, but lower in
the east of Asia than in the east of North America ; that whereas the
whole of the west coast of Norway, extending to beyond 70° N., is at
all times free from ice, the northern coasts of the peninsula of Alaska,
in about 57° or 58° N., are regularly beset by ice in winter; but, on
the other hand, whereas the eastern coasts of North America are
rarely encumbered by ice below the Gulf of St. Lawrence, in about 46°
or 47° N., ice is to be seen in the Chinese Gulf of Pechili below lat.
10°; and, again, Halifax, in Nova Scotia, in 441° N., is nearly always
cpen, and thus can serve as a winter-port for the Canadian Dominion ;
while the Russian seaport of Vladivostok, in the east of Siberia, to the
south of 43° N., is closed by ice for about a third part of the year.
With regard to cultivated plants, however, it must be mentioned that
shose which are able to profit by long and hot summer days during a
very short summer can be grown in higher latitudes in eastern Asia
than in eastern North America. Wheat, rye, barley, and even cucum-
bers, can be grown at Yakutsk in eastern Siberia, in 62° N. (the same
watitude as the mouth of the Yukon in Alaska, and Frederikshaab in
Greenland), the barley and wheat being sown in the first days of May,
and ripening about the middle of July—within two months and a half.
57. The land surfaces of the southern hemisphere are too narrow
bo exhibit the easterly increase in the extremes of temperature,
especially since they do not extend into those latitudes in which that
increase is most marked. One circumstance is, however, noteworthy
regarding the climate of the temperate zone of the southern hemi-
sphere, namely that it is generally colder, at least on the land, than in
corresponding latitudes of the northern hemisphere ; so that the limit
of cultivation of various plants is in a lower latitude to the south than
bo the north of the equator. A glacier descends in Chile to the water's
edge in about lat. 46° 8., a latitude corresponding to that of the middle
of France in the northern hemisphere. The orange is not cultivated for
its fruit in Victoria, except in the extreme north-west, in a latitude one
or two degrees below that of the southernmost point of Europe. In
the South Island of New Zealand, which is in as low a latitude as the
northern half of Italy, oats is the principal crop, as it is in Scotland
and Ireland.
58. As the winds are the carriers of heat and cold it follows that
she physical configuration of the land may indirectly affect tempera-
bure. Mountains, by obstructing winds, in some cases afford protection
from cold winds, in others prevent certain districts from getting the
benefit of warm ones. Temperature is also greatly modified by evapora-
ion and condensation of water vapour, evaporation always tending to
