The houses and rooms of persons infected with the plague are purified by firing gunpowder in them. At Moscow we employed with success a powder, called _antipestilential_, of which sulphur and nitre formed the basis; some bran and other vegetable substances, such as abrotanum, juniper-berries, &c. together with certain resins, were added; but in my opinion these resins are totally useless, and only increase the expence[73]. The acid vapours let loose on burning nitre and sulphur together, remain a long time suspended in the air[74]. The greater or less strength of these powders depends on the proportion of sulphur and nitre to the other ingredients. After burning the rags or other litter which may be found in the rooms, they are fumigated by throwing one of these powders on a chafing-dish or pan of coals, the doors and windows being shut, to keep in the smoke and vapour for a sufficient length of time. This vapour is hurtful to the lungs, and produces suffocation; hence the person who throws the powder upon the burning coals should get out of the room as fast as possible. This process is repeated three or four times in the space of twenty-four hours for several days together; after which the doors and windows are thrown open. D. _Of Preservative Remedies._ We shall content ourselves with abridging, rather than translating at full length, what the author offers on this head. Among other preservatives, _issues_ are taken notice of. The author himself had one made in his left arm, which he kept open for a twelvemonth; but he is inclined to attribute his exemption from infection rather to his having avoided the contact of the sick and infected goods, than to this remedy. It appears that four surgeons at the principal pest-hospital died of the plague, notwithstanding they had all of them issues. Hence their preservative virtues may be questioned; yet as they have been recommended by others, and are attended with little inconvenience, he thinks it would be proper for those who are obliged to go among the infected, to have one made in the arm or leg, or both.--_Sweet spirit of nitre_ was esteemed an excellent preservative by some; they took twenty or thirty drops of it upon a lump of sugar several times a day. Others took, with the same intention, the _Peruvian bark_ under different forms; but as they all kept out of the way of the contagion at the same time, the preservative powers of these remedies remain very doubtful. The common practice of carrying _camphor_ in the pocket or sewed in the lining of the clothes, has nothing to recommend it. In like manner the _smoking of tobacco_, though it has been so strongly recommended by _Diemerbroeck_ and others, is by no means a certain protection against the contagion. The Turks, says Dr. _Mertens_, are continually smoking their pipes; and yet great numbers of them are swept off by the plague every year.