Cultivation and drainage are now fully understood to be the basis by which a healthy condition of air is to be obtained, next to that, cleanliness and ventilation; if either be neglected a sickly, mouldy, and unwholesome contamination of atmosphere ensues; the odour of a bog is proverbially mouldy, and so is that of an ill-ventilated house or cellar; dryness, or the fresh pleasant scent of clean water, are the antagonists of these; the aromatic odours of vegetation are opponents of putrefaction, and consequently of the development of the lower forms of life. All empyreumatic matters prevent mouldiness and decomposition; and odours arrest and prevent the growth of mouldiness. The oil of birch, with which the Russia leather is impregnated, and which gives it so pleasant an odour, effectually prevents mouldiness, and consequently decay. Lindley says, "It is a most remarkable circumstance, and one which _deserves particular enquiry_, that the growth of the _minute fungi_, which constitute what is called mouldiness, is _effectually prevented_ by any kind of perfume."[71] Cedar has {182} been used, from time immemorial, for a like purpose; and I doubt not the recommendation of Virgil, before quoted, in reference to the burning of cedar, was founded on some practical utility of this kind, though its _modus operandi_ was unknown to him. Allied to these is a curious circumstance, and worthy attention. I copy the following from an old work on Pestilences. "It is remarkable that when the Plague raged in London, Bucklersbury, which stood in the very heart of the city, was free from that distemper; the reason given for it is, that it was chiefly inhabited by druggists and apothecaries, the scent of whose drugs kept away the infection, which were so unnatural to the pestilential insects, that they were killed or driven away by the strong smell of some sorts of them." "The smell of _rue_, and the smoke of tobacco, were prescribed as remedies against the infection; but especially tar and pitch barrels, which it was imagined preserved Limehouse, and some of the dock-yards from infection."[72] Pitch and tar dealers are everywhere spoken of as being remarkably exempt from infectious diseases. Cold infusion of tar was used in our colonies as a prophylactic against the Small Pox. Bishop {183} Berkeley was induced to try it when this disease raged in his neighbourhood. The trial fully answered expectation--for all those who took tar-water, either escaped the disease, or had it very slightly.