Some fumigations are produced by the volatilization of solid bodies, as camphor and carbonate of ammonia, or sal volatile;—some by the volatilization of liquids, such as vinegar, pyroligneous acid, and the various essential oils, as cinnamon, rose, thyme, mint, pennyroyal, carraway, and turpentine, while others are permanently elastic fluids or gases, as muriatic acid gas, chlorine, and ammonia. The first-mentioned substances, viz. camphor and ammonia, are not very strong, and may be disseminated through the apartment of the patient, even when he is present, without giving him any uneasiness. Carried about with those who visit the sick, and who are apprehensive of contagion, they are useful by affording a grateful odour, which hides disagreeable taints, and perhaps it is in that way chiefly that they are useful. The liquids which have been named above, have been long used for the purposes of fumigation, and in general, they may be employed even in the presence of the patient. A few of them may possibly decompose effluvia, but there is much reason to think that they are useful, for the most part, by hiding ungrateful odours, and imparting to the atmosphere, which is liable to be suspected as unwholesome, a delightful fragrance. Vinegar is much used for the purpose, and with very considerable benefit, and is therefore to be employed. The essential oils are capable of being diffused throughout the air, and with the assistance of heat, are often made available for the purpose of covering odours. When they are to be used, the oils should be poured upon a piece of live coal, held in the middle of the apartment; they are then immediately converted into vapour. In like manner, vinegar and the other volatile liquids may be disseminated through the atmosphere. The oils, the vegetable substances in which they are contained, tar and the like, are occasionally burnt with the same intention, and sometimes with advantage. The incense so much used by the ancients, was procured for the most part by the burning of the vegetable substances in which these essential and fragrant oils resided, by which part of them is diffused in vapour. The ostensible and pretended object of the priests, in offering up incense, while that and other religious rites were performing over the bodies of deceased persons, was the conciliation and propitiation of the Deity. But while this was the sole ostensible object of the priests, and that which was held by the people, as the only and exclusive purpose proposed, there is good reason to believe that the offering up of incense, like many other observances of religion, had its temporal, and worldly, as well as spiritual ends; and that the sweet smelling odours, which were thought would be so grateful to Heaven, were, on those occasions, used in no small degree, as so many fumigations, to defend the pious and resigned priests from the effluvia of the dead body, and the consequent corruption of the atmosphere.