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country, and cholera disappears. Should it be admitted that the annual
disappearance of cholera is caused by its being drowned out by the annual
flooding during the rains, it must still be allowed that there are other seasonal
influences which control its causes at other seasons. Is it the subsoil water ?
There is a steady fall of the level of the subsoil water during the last three
months of the year, during which cholera reaches its greatest prevalence.
During the month of October (1877) the level of the subsoil water fell from
6 feet on the 1st to 7 feet 71/2 inches on the 31st, i.e., it fell 1 inch every day,
and the fall was steady. In November the fall was still more rapid, being
at the rate of 13/5 inches in the first half of the month and 2 inches daily in
the second, the total fall during November being 4 feet 6 inches. In Decem-
ber the fall was not so rapid, but it was from 12 feet 3 inches from the 30th
November to 14 feet 10 inches on the 31st December, or exactly 1 inch
every day. But in January the level of the subsoil water is still falling, and
the prevalence of cholera becomes greatly mitigated. In 1877 the observations
at Dhaka show that it fell steadily through 1 foot 5 inches during January,
and the deaths in the district fell from 2,700 in December 1876 to 1,100 in
January 1877. During February the subsoil water-level fell 28 inches, and
the deaths were not 450. On the 1st March it was 18 feet from the surface
of the ground, and it fell 7 inches between the 1st and 21st and then began
to rise, rising 6 inches during the remaining ten days of the month. The
deaths from cholera were 400. The level of the subsoil water rose 20 inches
in the first 17 days of April, and fell 22 inches by the end of the month, and
stood 18 feet 2 inches on the 3lst. There were 1,300 deaths from cholera
during the month. During the month of May the level fluctuated. It fell
during the first week, rose 10 inches in the second week, and fell 4 inches
in the third week, and remained nearly stationary till the end of the month.
The deaths from cholera were 650. In June it rose rapidly during the first
half of the month, and fluctuated during the second. Cholera had now nearly
disappeared. On the 1st July the subsoil water was 5 feet 4 inches from
the surface, and it rose to 4 feet 3 inches on the 21st, falling .towards the
end of the month. The country was now under water, and there was no cholera.
In August the level was still rising, but in September it fell from 6 feet 2
inches on the 1st to 9 feet 4 inches on the 3lst, but the country was still under
water, and there was no cholera. The following statement will show what
relationship, if any, existed between the level of the subsoil water and the
prevalence of cholera in this district:—
Months.
January
...
February
March
•••
April
May
June
July
August
,
September
October
•••
November
,..
December
Subsoil water.
Falling steadily ...
...
...
Ditto
Falling for three weeks ; rising at end of month. . .
Fluctuating between 18 and 20 feet from surface ..
Fluctuating slightly
First half rising rapidly, second half fluctuating , .
Rising from 5 feet 4 inches to 4 feet 2 inches from
Surface.
Still rising slightly and fluctuating ...
...
Falling steadily from 6 feet 2 inches to 9 feet 4
inches.
Falling steadily ...
.,.
,..
,,,
Ditto
Ditto
Cholera.
Decreasing.
Ditto.
Ditto.
Very prevalent everywhere.
Disappearing, except at Rupjan.
Had almost disappeared.
No cholera.
Ditto.
Ditto.
Cholera reappearing.
Cholera raging.
Ditto.
From March to June the level of the subsoil water is influenced by the
tides, and it probably fluctuates with a good deal of freedom through the
sandy soil of the district. On this account the level is noticed to rise and fall
daily, and the exact level cannot of course be given during these months.
From October to February the influence of the tides is not felt so much,
because during these months the rivers are falling, and the subsoil water falling
more slowly with them does not feel the influence of the tides in an appreciable
manner. From July to September the rivers are not tidal. Taking everything
into consideration, it cannot be said that there is any parallelism between the
fluctuation of the subsoil water-level and that of cholera in this district.