THE third Cause we assigned for the spreading of _Contagion_, was a corrupted State of _Air_. Although the _Air_ be in a right State, yet a sick Person may infect those who are very near him: As we find the _Pestilence_ to continue sometimes among the _Crew_ of a Ship, after they have sailed out of the Infectious Air wherein the Disease was first caught. A remarkable Accident of this Nature is recorded to have happened in the _Plague_ at _Genoa_ in the Year 1656. Eleven Persons put to Sea in a _Felucca_, with design to withdraw themselves from the _Contagion_, and retire into _Provence_; but one of them falling sick of the _Plague_ soon after they had imbarked, infected the rest; insomuch that others being taken ill, and dying in their turns, they were not admitted any where, but were forced to return from whence they came: and by that time the Boat arrived again at _Genoa_ no more than one of them survived[55]. HOWEVER in this Case the Malady does not usually spread far, the _contagious_ Particles being soon dispersed and lost. But when in a corrupt Disposition of the _Air_ the _contagious_ Particles meet with the subtile Parts generated by that Corruption, by uniting with them they become much more active and powerful, and likewise of a more durable Nature; so as to form an infectious Matter capable of conveying the Mischief to a greater distance from the diseased Body, out of which it was produced. IN general, a _hot Air_ is more disposed to spread _Contagion_ than a cold one, as no one can doubt, who considers how much all kinds of _Effluvia_ are farther diffused in a _warm Air_, than in the contrary. But moreover, that State of _Air_, when unseasonable Moisture and want of Winds are added to its Heat, which gives birth to the _Plague_ in some Countries, will doubtless promote it in all. For _Hippocrates_ sets down the same Description of a _Pestilential State_ of Air in his Country, as the _Arabians_ do of the Constitution, which gives Rise to the _Plague_ in _Africa_[56]. _Mercurialis_ assures us the same Constitution of _Air_ attended the _Pestilence_ in his time at _Padua_[57]: and _Gassendus_ observed the same in the _Plague_ of _Digne_[58]. Besides, it is easy to shew how the _Air_, by the sensible ill Qualities discoursed of in the last Chapter, should favour infectious Diseases, by rendering the Body obnoxious to them.