3. Desquenette tells us, the infection of the plague never crosses the Nile, and that it is arrested by means of ditches, dug and filled with water for that purpose. Dr. Whitman has remarked, that the plague never passes from Abydos, on the Turkish, to Mito, on the European side of the water of the Dardanelles, which forms the entrance to Constantinople. The yellow fever has never been known to pass from Philadelphia to the Jersey shore, and the miasmata generated on the east side of the Schuylkill rarely infect the inhabitants of the opposite side of the river. Many persons found safety from the plague of London, in 1665, by flying to ships which lay in the middle of the Thames, and, it is well known, no instance of yellow fever occurred in those Philadelphia families that confined themselves to ships in the middle of the Delaware, in the year 1793. But three or four, of four hundred men, on board a ship of war called the Jason, commanded by captain Coteneuil, perished with an epidemic yellow fever, in the year 1746, at St. Domingo, in consequence, Dr. Desportes says, of her hold being constantly half filled with water[19]. I have multiplied facts upon this subject, because they lead to important conclusions. They show the immense consequence of frequently washing the streets and houses of cities, both to prevent and check pestilential fevers. What would be the effect of placing tubs of fresh water in the rooms of patients infected with malignant fevers, and in an atmosphere charged with putrid exhalations? Their efficacy in absorbing the matter which constitutes the odour of fresh paint, favours a hope that they would be useful for that purpose. I have mentioned an instance, in the Account of the Yellow Fever in Philadelphia, in the year 1797, in which they were supposed to have been employed with evident advantage. [19] Vol. I. p. 161. 4. Intercepting the passage of miasmata to the inhabitants of cities. Varro, in his Treatise upon Agriculture, relates, that his namesake Varro, a Roman general, was in great danger of suffering, with a large fleet and army, from a malignant fever at Conyra. Having discovered the course of the miasmata which produced it to be from the south, he fastened up all the southern windows and doors of the houses in which his troops were quartered, and opened new ones to the north, by which means he preserved them from the fever which prevailed in all the other houses of the town and neighbourhood. Mr. Howard advises keeping the doors and windows, of houses which are exposed to the plague, constantly shut, except during the time of sunshine. Several other means have been recommended to preserve cities from malignant fevers during their prevalence, which are of doubtful efficacy, or evidently hurtful. They are,