e mean summer temperature
was only 58.1 deg. F. against 189 in 1862, when the mean temperature was
59.0 deg.. In 1879, when the mean temperature was 58.7 deg., the deaths from
diarrhoea rose to 228 per million, but a few days were unusually hot. In
1877 the mean temperature of the air was 61.2 deg., of the Thames water 63.3 deg.,
and the mortality of infants from diarrhoea 347 per million population. In
1874, when the mean temperature of the air was 61.7 deg., the mortality rose
to 447 per million; and in the hot summers of 1878 and 1876, when the mean
air temperatures were 64.1 deg. and 64.9 deg. respectively, the death-rates of
infants were 576 and 642 per million population. The relations, therefore,
between a high summer temperature and the mortality from diarrhoea in
infants are very intimate. I have selected the mortality among infants in
preference to that at all ages, as the deaths occur more quickly, and
because young children suffer in greater proportion than other persons.

The proportionate number of deaths at _all ages_ from diarrhoea corresponds
pretty closely with those of infants. To prove this, I made calculations
for three years, and ascertained that only 3.9 per cent. of all the deaths
from this disease were registered in the weeks having a temperature of
less than 50 deg.; 11.9 per cent. in the weeks having a temperature between
50 deg. and 60 deg.; while in the comparatively few weeks in which the temperature
exceeded 60 deg. F., as many as 84.2 per cent. of the total number of deaths
was registered. In the sixteen years, 1840-56, for which many years ago I
made a special inquiry, only 18.9 per cent. of all the deaths from
diarrhoea occurred in winter and spring, against 81.1 per cent. in summer
and autumn. In the twenty years, 1860-79, there were seven years in which
the summer temperature was in defect when the mortality per 100,000
inhabitants of London was 200; while in ten summers, during which the
temperature was in excess by 2 deg. or less, the mortality was 317 per
100,000. The mean temperature was largely in excess, that is to say, more
than 2 deg. plus in three of these summers, when the mortality reached 339 per
100,000 inhabitants.

These figures show that great care should be taken in hot weather to
prevent diarrhoea, especially among young children; by frequent washing
with soap and water to insure cleanliness, and proper action of the skin;
by great attention to the food, especially of