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   But from the many gardens situated on the plains of Sibsaugor and Lakhim-
pur or other places comparatively healthy as regards malaria not a single
case has been recorded.

   In the Duars we find a system known as " voluntary labour," a system which
entails a great influx and efflux of labour far beyond that in the worst gardens
on the " indentured labour " system. So marked is the shifting character of
the population under these conditions that we have the unique phenomenon of
the whole population of a district living under conditions which resemble those
seen on any large engineering undertaking in the tropics and involved in
the general scheme are the Europeans and babus, who form the subject of our
present investigation, since it is they who, whatever one believes to be the
reason, demonstrate these conditions of industrial aggregation by the occurrence
of Black-water Fever amongst them.

   As it is in the Duars that Black-water Fever is most prevalent, this
district will serve us best for the closer study of the conditions under which Black-
water Fever occurs.

THE DUARS.

   The district known as the Duars lies along the foot of the Eastern Himalayas
between Nepaul and Assam. To the west, and for all practical purposes a mere
extension of the Duars, is the Darjeeling Terai.

   The rainfall in the Duars is very heavy, averaging about one hundred and
fifty inches in the year, and this, together with the configuration of the land,
which abuts immediately upon the foot of the mountains, is very favourable