“But, in opposition to this, _Rhazes_ lived 120 years, an often practised in plagues. _Hodges_ remained in town, and attended the sick, during the great plague in 1665. _Kaye_ was in the midst of practice in the sweating sickness in 1551, without any inconveniency. _Procopius_ informs us, that during a terrible plague at Constantinople, in 543, which almost destroyed the whole city, no physician nor other person got the plague by attending, dressing or touching the sick. Yet most of the Capuchins, the Jesuits, the Recollets, the Observantines, the Barefooted Carmelites, the Reformed Augustines, all the Grand Carmelites, the Grand Trinitarians, the Reformed Trinitarians, the Monks of Loretto, of Mercy, the Dominicans, and Grand Augustines, who kept themselves secluded in their several convents, and took every precaution to avoid the plague, while it raged at Marseilles, perished by it. “There are no epidemical nor contagious diseases that attack every person who breathes the same air, or that is in contact with the infection, else whole regions would be depopulated. The habit must be graduated, or adapted, for the reception of a disease. In some constitutions of body the access is easy, in some difficult, in others impossible. _But where the revelation of this mystery is to be found, none can tell._” In this, which our author seems to have designed as his _grand argument_, it is plain that the deficiency is as great as in any of the rest. If we suppose the plague, or any other epidemic disease, to arise from some general cause, let that cause be _contagion_ or any thing else, it ought to operate upon all who come within its sphere of action, as Dr. Mosely observes of _infection_. If experience shows that it does not, the argument will hold equally against a constitution of the atmosphere, putrid effluvia, heat, cold, or any thing else; and in fact the Doctor fairly gives up the point at last, by resolving the whole into an _unrevealed_ mystery. With regard to what he says about the plague at Marseilles getting into the convents, of which he presents us with such a catalogue, it is impossible to know what precautions were used, and we are assured that in Turky it is thought necessary for the Europeans not only to guard against a communication with their own species, but some of the brute creation also. Cats particularly are dreaded so much, that a general massacre of them commences among those who use precautions, the favourites of that species must be sent to a distance, and M. Volney mentions two merchants who had shut up their houses, and yet had the plague imported by a cat. In short, considering that infection is supposed to be altogether invisible and imperceptible, it is impossible to say how it may be conveyed, or to what extent it may occasionally act when once brought into a country. Dr. Fordyce is of opinion that the distance at which infection may act depends on the disposition of the air at the