2. Calomel, taken in such small doses as gently to affect the gums. It preserved most of the crew of a Russian ship at Plymouth, in the year 1777, from a fever generated by filth in her hold. In a letter which I received from Captain Thomas Truxton, in the year 1797, he informed me, that an old and respectable merchant at Batavia had assured him, he had been preserved in good health by calomel, taken in the way that has been mentioned, during the sickly seasons, for upwards of thirty years. The mortality of the fevers of that island may easily be conceived of, when I add, on the authority of a physician quoted in Sir George Staunton's Account of his Embassy to China, that one half of all new comers die there on the first year of their arrival. Our principal dependence should be placed upon those two preventives under this head. There are several others which have been in common use, some of which I believe are hurtful, and the rest are of feeble, or doubtful efficacy. They are, 3. Wine and ardent spirits. They both prevent a malignant fever, only when they excite an action in the system above that which is ordinarily excited by the miasmata of the fever; but this cannot be done without producing intoxication, which, to be effectual, must be perpetual; for the weakness and excitability, which take place in the intervals of drunkenness, predispose to the disease. Agreeably to this remark, I observed three persons, who were constantly drunk, survive two of our most fatal epidemics, while all those persons who were alternately drunk and sober, rarely escaped an attack of the fever. In most of them, it terminated in death. 4. Tobacco. Many hundreds of the citizens of Philadelphia can witness, that no benefit was derived from this weed, in any of the ways in which it is commonly used, in the late epidemics of our city. Mr. Howard says it has no effect in preserving from the plague. 5. Camphor suspended in a bag round the neck, and rags wetted in vinegar, and applied to the nose. These means were in general use in the fever of 1793, in Philadelphia, but they afforded no protection from it. It is possible they had a contrary effect, by entangling, in their volatile particles, more of the miasmata of the fever, and thus increasing a predisposition to it.