Page:McCosh, John - Advice to Officers in India (1856).djvu/246

 elements in the atmosphere; and till chemistry attains to that extreme perfection, we must be content to use the old fashioned terms malaria and contagion to explain our meaning; and our theories without meaning. This miasma is generated more readily in Autumn than during other seasons of the year; is more potent at full and new moon than at other periods of lunation;and more active between sunset and ten o'clock, than during the rest of the day. Miasma seems to possess gravity; soldiers that sleep on the ground-floor are more sickly than those that sleep on the second or third story. European settlers preserve their health in the Sunderbands of the Gangesby living in lofty houses; and in the forests of Malacca, some wild tribes actually roost upon lofty trees; indeed, the distribution of miasma is directed by the same laws that are applicable to smoke or fog.

Miasma is liable to be dissipated by heat; a moist atmosphere is more favourable for its action than a dry one, and a person may sleep in a marsh with impunity, if beside a watch fire. Miasma may be conveyed by the wind to a considerable distance, with its properties unimpaired. A ship may anchor, and a regiment may encamp a mile distant to windward of a marshy island without suffering; whereas,if so situated a mile to leeward, both would suffer from fever. An army may encamp with safety on the sea-shore of a