1895-96.] Mr E. C. Mossman on Death-rate in Edinburgh. 109 
by the middle of December. The lowest death-rate occurs in the 
middle of July. 
Fig. 7. — Croup and Laryngitis i and Fig. 8, Diphtheria. 
The curves for the above diseases being based on only ten years’ 
observation, it would be premature to draw conclusions, further 
data being required to define the seasonal variations. 
Fig. 9. — Diarrhoea. 
The death-rate from diarrhoea is above the mean from June to 
October, being at a maximum about the beginning of September, 
when the mortality is over 150 per cent, above the annual average. 
The minimum occurs in March. 
Fig. 10. — Bronchitis , Pneumonia , and Pleurisy. 
The curve of these three diseases of the respiratory organs closely 
follows that of deaths from all causes, being above the mean from 
October to April, and below it during the other half of the year. 
An intimate relationship exists between the mortality from respira- 
tory diseases and the variability of temperature as deduced by the 
method described ; the more changeable the weather the greater 
the mortality. This will be clearly seen on examining the curves 
of mean temperature and mean variability of temperature, and 
comparing them with the curve of deaths from the three diseases 
under review. The most changeable weather, it will be seen, 
occurs not during the cold spell at the beginning of January, 
but at the end of November, when the mortality from respiratory 
diseases is at a maximum. This is not a local phenomenon, the 
greatest death-rate from these diseases in London being observed at 
this time. In order to show more clearly the prejudicial effect of 
changeable weather, we have examined the weekly mortality returns 
for these diseases for the ten years 1885-94. We have corrected 
the values so as to allow for increase in population,* the returns for 
each year being thus strictly comparable with each other. The 
* For some years prior to the taking of the census in 1891, the population 
of Edinburgh had been over-estimated, but Dr Blair Cunynghame kindly 
sent me the corrected numbers for each year. 
