An inquiry into the propagation of contagious poisons, by the atmosphere

by Somerville Scott Alison

In such situations, it is not uncommon to observe lights floating along during the night, and superstition has not failed to make them represent evil spirits. They are known by the name of “Will o’ Wisp” and “Jack o’ Lantern;” and have, on many occasions, proved objects of no slight dread to many ignorant persons. The lights are merely ignited carburetted hydrogen gas,—the same kind of gas as that used for lighting our shops and houses.

The gas is ignited, perhaps, by the rising to the surface of the putrid water, of a bubble of phosphuretted hydrogen, which, as was before observed, burns the moment it comes in contact with the atmosphere.

Other products of an aeriform kind may be evolved also, but we have no direct evidence of their existence,—but an atmosphere, loaded with vapours of the kind mentioned, is enough to account for the production of the observed disease, in all its varied forms, when there is conjoined with it other unwholesome agencies. In some countries, the pestilential air is present throughout the year, for instance, in the country around Rome, in the fens of Lincolnshire, where ague is seldom absent; in others it is periodical, chiefly confined to the hot and rainy seasons, as in India and in the West Indies, where fevers prevail to a great extent; and in others, again, it is observed only when the wind blows from a particular direction.

These effluvia are conveyed to a distance by currents, and produce their peculiar effects, more or less, upon almost all they encounter. The malaria at Rome is carried by the wind into the city, by the channels most open to its entrance; and those parts, it is said by medical men who reside there, that are most exposed to the wind blowing off the adjacent marshy grounds, are most unhealthy. It is for that reason that the suburbs are more unwholesome than the interior of that city, where the wind does not find ready access, on account of the obstacles offered to its course by the high buildings. The high houses and streets thus act as a barrier against the entrance of the pestilence, and it is even said that the narrowest streets there, are the most healthy, as they shut out the pestilential vapour.

An obstacle of the same kind is offered by hills which interrupt the course of winds carrying with them vapours from marshy grounds. In the West Indies, where the yellow fever commits such frightful ravages, many instances are known where a town or district retains its health, from the shelter which a hill affords against the visitation of a wind that has loaded itself with deadly miasms, while sweeping over a marsh or swamp. It is the practice of those residing in those countries, not only to remove from the swamps, but also from those points to which the wind blows after passing over them.

Inattention to that consideration has led to the loss of much human life, and to the fruitless expenditure of much money in the erection of houses, barracks, and the like, which, after completion, have been found to be totally uninhabitable, from the pestilential vapours carried to them by the winds. In illustration of the influence of winds, we submit the following interesting extract from Dr Good’s Study of Medicine. He has been speaking of effluvia from animal matter. “But the foul and stinking Harmattan,” (a pestilential wind) “when it rushes from the south-east upon the Guinea coast, loaded with vegetable exhalations alone, with which it impregnates itself while sweeping over the immense uninhabitable swamps and oozy mangrove thickets of the sultry regions of Benin, triumphs in a still more rapid and wasteful destruction; so much that Dr Lind informs us, that the mortality produced by this pestilential vapour in the year 1754 or 1755 was so general, that in several negro towns, the living were not sufficient to bury the dead; and that the gates of Cape Coast Castle were shut up for want of sentinels to perform duty. Blacks and whites falling promiscuously before this fatal scourge.”

So loaded is the air on some occasions with these pestilential vapours, that they attach themselves to whatever objects they meet, houses, the sides of hills, and woods, through which they pass along with the wind, and so completely has a wood stripped the currents of their baneful accompaniments, that they have been respired after with no injury whatever.

Trees are found to give great shelter and salubrity to towns in this way, acting as they do as so many sieves retaining impurities.

It is understood that the effluvia arising from putrefying vegetable matters ascend high in the atmosphere under the influence of the solar rays, and spread far and wide, and that at night during the cold they fall with the dew to the ground again, and impart to it and to those exposed to its action, much virulence. The ground is there known to be extremely unwholesome, and those who have been compelled by want, by sickness, while travelling, overtaking them, or by being benighted, to lie down with nothing but the soil for a couch, and with no shelter from the vapours and dew that falls at night, save the sky itself, have felt this pestilential influence: on the morrow they awake distressed, parched, and affected with headach, and the usual symptoms of malignant fever.

With the close of day or the setting of the sun, the pestilential vapour falls and envelopes the country and the habitations of men with a deadly mantle—and it is then unsafe to venture into the open air in many of the finest countries of the world.