27
The horizontal scale is six days to one inch ; the vertical scale varies as shown
in the left hand margin. The information compiled in this chart has been obtained as
follows :—
The maximum and minimum temperatures, humidity, velocity of wind, and
amount of clouds have been obtained from the published records of the Colaba
Observatory. The population has been obtained from the Managing Director of,
the Tramway Company, who has based his returns on the averages of Tramway
receipts, extending over several years. These returns have been checked with the
information supplied by the Collector of Bombay, and as they agree within a
few thousands, they may therefore be taken as substantially correct. The daily
mortality, from the Cemetery returns of the Municipal Health Department,
The normal mortality, the average of five previous years from the returns
published in the Government Gazette. The red figures at the top of the Chart
are the total deaths from all causes for the month, and the red figures at the
bottom of the chart are the total deaths from Plague.
The total number of deaths from Plague has been arrived at in the following
manner :—
The total weekly average number of deaths, during the five years previous
to the Plague, has been deducted from the total deaths from all causes for the
week, and the remainder taken as the number of deaths due to Plague, deaths
from Cholera being shown separately, but owing to the decrease of population,
there must be added, in order to arrive at a true conception of the increased
mortality a figure bearing the same proportion to the recorded deaths as the cal-
culated actual population bears to the normal population of 8,50,000. This
calculation has been made, and the figure or number to be added is given in red
figures above the numbers for estimated deaths from Plague by months, entered
at the bottom of the Chart.
The object of the compilation of this Chart was to establish the truth or other-
wise of some of the theories freely advanced regarding the definite influence of
temperature, humidity, wind and clouds on mortality. Northerly and Easterly winds,
which are always dry, seem generally to have had an unfavourable influence, often,
immediately so, on the mortality, e.g., from November to near the end of March when
the humidity is generally between 60 and 70, and while Easterly winds prevail the
mortality increases irregularly, but more or less steadily ; and in particular cases, e.g.,
on the 8th and 9th February 1898 and on the 2nd March 1898, when high winds
were accompanied by a fall in the Humidity, there were immediate increases in the
deaths, as shown in the Chart.
There has not, however, been a sufficiently consistent sequence to make any
generalisation possible. As a matter of fact, in order to have given the elements a
fair chance, all Plague measures would have to be abandoned, for it cannot be doubted
that the measures that have been adopted in Bombay have had the effect of diminish-
ing the extent of the pest. The degree of sanitary efficiency is also a disturbing
factor.
It would appear that a low temperature may have had an adverse bearing on the
disease, as, throughout the months of December, January and February, when the
minimum temperature is the lowest for the year, the mortality is greatest.
The chart is interesting in showing the movements of the population. In the
first epidemic the population fell from 8,50,000 to 4,37,000 in the middle of February
1897. In the second epidemic the lowest recorded population is 7,10,000, about