Exhalation, generally speaking, denotes effluvia or steams which arise from the surface of the earth, or other bodies, in the form of vapour.

Plants and flowers afford a grateful exhalation, provided their fragrance be not too strong : hence they should never be placed in confined apartments, as instances have occurred of persons being almost suffocated, by sleeping in rooms where quantities of fresh flowers were exposed. In serene weather, however, fresh plants or ever-greens (but by no means flowers) may be strewed with advantage, during the day, in the apartments of valetudinarians; as such vegetables, especially, in sun-shine, generate a vital air, which produces salutary effects on the lungs.

The exhalations arising from vast numbers of burning candles, as also from the breath of many persons re»piring in the same room, are peculiarly unwholesome to-weak and consumptive habits. This inconvenience may, however, be remedied by means of conical tubes, the funnels or broad ends of which should be placed so as to communicate in or above the win-dows, with the open air: thus, the latter will be impelled into the rooms with considerable force, and ventilate them more effectually, a d at much less expence than is accomplished by fumigations, or other methods.

The vapour arising from charcoal is particularly hurtful; and, in close apartments, often productive of fatal accidents: the greatest precaution is therefore requisite, when chorcoal is employed for culinary or domestic purposes. In a similar manner, humid air of every kind is very detrimental to health ; and we seriously reprobate the keeping of damp linen, wet clothes, and even wet umbrellas in dwelling-rooms ; as, by paying due attention to this circumstance, many serious accidents might easily be prevented.