0th
degree, in latitudes whose mean temperature is below the
freezing-point; while in Switzerland, corn ceases to ripen at 9
degrees above the same point, and in the plateaux of South America, at
22-1/2 degrees--a fact which goes to shew, 'that the growth of grain
is much more dependent on the summer temperature than on the annual
mean. The long summer days of the polar regions afford a very brief,
but a comparatively exalted summer heat.' It is, however, only the
barley which ventures so far north: the limit of rye is 67 degrees, of
oats, 65 degrees, of wheat, 64 degrees, on the west side of the
peninsula, and from 1 to 2 degrees less on the east. In Southern
Norway, the spruce-fir ceases to grow beyond the line of 2900 feet
above the sea-level; while in Switzerland, it is commonly met with at
the height of 5500 feet, and in some situations, 7000; shewing that
the influences which affect the growth of grain do not similarly
affect that of trees--proximity of the sea decreases the summer
temperature. Again: 'In Scandinavia the tree-limit is indicated by the
birch; in the Alps, by firs. The two lower mountain zones of the
Alps, the regions of the beech and the chestnut, do not exist in the
Scandinavian mountains. Compared with the climate and tree-limits, the
cultivation of corn does not go so high in the Alps as it does toward
the north; for it ceases about with the beech in the Alps, and grazing
is the regular pursuit in the region of firs; while in Scandinavia,
the beech only goes to 59 degrees, and corn-culture to 70
degrees--that is, as far as the conifers. Corn succeeds in the latter
under a mean temperature below the freezing-point, while in the Alps
it ceases at 41 degrees Fahrenheit. The cause of this is the hot
though short summer of the north. The Alps have maize and the vine,
which will not grow around the Scandinavian mountains; the meadows are
throughout richer in the Alps, and grazing is therefore much more
extensively pursued.'

The peculiarities and comparisons afforded by other countries, are not
less interesting than those we have selected, and we might multiply
instances, if space permitted. Enough, however, have been adduced to
shew that the mode of accounting for differences of vegetation is so
far satisfactory, that it appears to be in perfect accordance with
discoverable natural laws; and it is no longer a surprise or mystery
to find plants of Southern Russia and of Asia Minor on the high
table-