CLIMATE

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purchased a species of immunity from long acquaintance
with the malarial demon.
But this bane of fever is by no means confined to
the districts where vegetation is rank. It pervades the
agricultural districts of the plains and the streets of great
cities alike. It knows no distinctions of locality except in
degree. It follows the course of irrigation, and appears
with special virulence wherever the earth is freshly upturned
 in places which have long lain undisturbed. As
the season wears on and the drying process is gradually
completed, when the shorter days are cooler and the
breath of the cold weather is distinctly felt, fever gradually
diminishes. By December all the northern forests and
valleys are comparatively safe, and the sportsman goes
abroad with freedom until the end of the hot weather in
June. During the first month or so of the rains, before
the earth is saturated, there is comparatively little risk.
Local irrigation and flooding have rendered many a station
in the Punjab and along the frontier of the Derajat
notorious for malaria, where once it was comparatively
unknown. It is during the annual desiccation of the
paddy fields, where rice has been cultivated in the Peshawur
 Valley, that the fever poison is especially active and of
a peculiarly malignant character. It is not the humidity
of the monsoon alone that is accountable for the widespread
 character of autumn unhealthiness in Northern
India. The ordinary processes of cultivation by means
of irrigation have a large share in the development of
poisonous influences, and some of the severest of the
periodic outbreaks occur in districts where there is comparatively
 little vegetation beyond the ordinary growth of
crops.
Within the limits of tropical India the duration of the
healthy season in jungle-covered districts greatly diminishes.
This is no doubt due to the gradual prolongation of the
rainy season, as the action of the north-east monsoon in
succession to that of the south-west becomes more and
more developed, whilst at the same time the sun’s rays
remain effective for mischief for a longer period. There