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to the difference in the nature of their water-supply. The Statement showing
the distribution of the coolies along the main road also supplies many similar
examples.
Γη further proof of the relation between the manifestation of cholera and the
condition of the water-supply, I would refer to what is stated in para. 85 of the
effect of the prohibiting the use of the water of the tank at Seonee, and to the
account given of the water-supply of Nagpore. In the latter instance, the immu-
nity from cholera of the population, as long as they were confined to one particu-
lar source of supply ; the reappearance of the disease as soon as water from other
sources became available; the effect of closing a set of wells evidently liable to
contamination by the percolation of surface water containing sewage matters;
and lastly, the very remarkable excess of mortality from cholera, occurring in the
course of two successive epidemics, among women employed in washing clothes
in tanks containing water derived from the surface drainage of the city area,—are,
I think, incontrovertible facts in support of the doctrine that, as regards the
general population of the country, an impure water-supply is the chief condition
under which cholera manifests itself.
259. With regard to the different forms of water-supply and their liability
to pollution, the open springs and small surface wells, so common in the trap
formation, are undoubtedly the worst; the most fatal out-breaks of cholera occur-
red in villages dependent on this form of water-supply. Many are mere shallow
puddles; others being not more than 6 feet deep, the surface drainage readily finds
its way into them between the impermeable rock and the thin stratum that
overlies it, while the ground sloping towards them is almost invariably fouled.
Wells also in very porous formations, and retaining but a few inches of water in
the hot weather, are dangerous sources of supply. A well sunk from 25 to 30
feet in clay or alluvial soil, and containing 3 to 6 feet of water in the hot weather,
I believe to be the safest of the ordinary sources of supply. In no village
dependent solely on such source of supply did I find that cholera had prevailed.
Where there is a tank or stream, as well as a well, it is very difficult to ascer-
tain to what extent each source of supply is resorted to, How far the larger
rivers are dangerous sources of supply, when not made the depositories of the
dead from the villages in their neighbourhood, may be better estimated when it
is ascertained that the practice has been stopped. Stringent orders have been
issued against it, and comparatively few of the villages on the banks of the Hirun
and Nerbudda that suffered severely in 1868, appear in the.returns oí the present
year, and in those that have been visited the mortality has been slight. In many
villages on the smaller streams the mortality was great ; it appeared to vary,
however, with the character of the streams; those villages dependent on the semi-
stagnant pools of the streams in the trap formation, as Myra and Kyra on the
Sagur (para. 94), and the villages round Heerapore (para. 119) suffered severely;
while in the villages on the Hugni, a sluggish weedy stream in the Oehora per-
gunnah, the mortality was slight; and villages on the Burnoo, a rapid stream
with a sandy bottom, in the same neighbourhood, escaped altogether. The
villages on the Kutna river too experienced remarkable immunity.
260. In estimating the effects of the waters of different streams in relation
to cholera, the different strata in which they flow must be taken into account.
It is probable that the condition of the organic impurities in water would he
modified by the presence or otherwise of certain salts ; and it may be that there
is some relation between the absence of vegetation, in the clear weedless waters
of the trap rivers, and the higher rate of mortality among the population depen-
dent on them for water.
261. Many instances are given in which a population dependent solely or
in part upon a tank for water suffered severely from cholera, as the towns of