Epidemics considered with relation to their common nature, and to climate and civilization : in two lectures delivered at the Philosophical Institution, Edinburgh, November 1855 / by Southwood Smith.

  • Smith, Southwood, 1788-1861.
Date:
1856
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Licence: Public Domain Mark

Credit: Epidemics considered with relation to their common nature, and to climate and civilization : in two lectures delivered at the Philosophical Institution, Edinburgh, November 1855 / by Southwood Smith. Source: Wellcome Collection.

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    MAIN CONSTITUENTS OF CLIMATE. LECTURE II. ON CLIMATE AND CIVILIZATION. Ladies and Gentlemen, Having given you some account of the general characteristics which Epidemics possess in common with each other, I am now to consider them with relation to Climate and Civilization. The principal constituents of the atmosphere maintain their equilibrium steadily over the whole surface of the globe. There is scarcely any difference in the relative proportion of its oxygen and nitrogen in the torrid zone and in the arctic regions. Whatever influence the atmosphere may have on climate must consequently depend on something adventitious to it and not in anything forming a part of it. Possibly therefore that something may be, in some degree, under human control. The main constituents of climate are temperature and moisture, and these are the climatic conditions that exercise the greatest influence on epidemics. Minor but still important conditions are the nature of the soil, the proportion of land that is cleared and under cultivation, the extent of forests, lakes, and rivers, the prevailing winds, the electrical state of the atmosphere, and so on, The temperature is highest where the sun's rays are vertical, or nearly so; where the sky is cloudless ; where the day is longest; and where there is the smallest difference between the fervid noon-tide heat and the temperature of the short night. The moisture is greatest where in addition to all the other sources of humidity there are periodical rains. In the countries subject to these rains, the entire extent of the level and low land is often covered a foot deeper with water than before the rains set in-