THE most common Manner of conveying and spreading a Contagion, observable in the preceding historical Collections, and which also is the Case of our present Apprehensions from Abroad, is by infected Persons, and Merchandize; it being attested by too many Facts to admit of the least Doubt, that even Packs and Bails of Goods carry the poisonous _Miasmata_ about with them; and from the Nature that we here suppose this Poison to be of, nothing is more likely to preserve it than animal Substances, as Hair, Wool, Leather, Skins, _&c._ because the very Manner of its Production, and the Nature of its Origin, seems to give it a greater Affinity with such Substances than any other, and to dispose it to rest therein until by Warmth, or any other Means of Dislodgement, it is put into Motion, and raised again into the ambient Air. TO know how these _Effluvia_ come to have such fatal Influences over Mankind, and to understand their Progression from the first Seizure, to the End of that Distemper they gave Birth to, requires too many _Precognita_ from the Mechanism of the animal OEconomy, and the Agency of such minute Instruments, to be particular about, in the Compass here limited. And a Reader who is duly fitted for such Enquiries, will find the utmost Satisfaction from _Bellini_ of _Fevers_, and Dr. _Mead_ of _Poisons_; how the Blood, and all the Secretions therefrom, are affected, and changed by such Causes. WE shall here therefore only suggest some Hints concerning the Suddenness of their Seizure, and their Energy of Operation. And this will not be difficult to conceive by those who are acquainted with that universal Property of Matter, whereby it is more or less determined to draw, and unite again, when separated into Parcels, according to the greater or lesser Affinities of their Figures, Solidities, and Quantities of Motion. As nothing therefore in Nature is supposed to bear a greater Similitude, than in this Case the natural animal Salts do with what hath been subtilized and set on Float in the Air, it can be no Wonder that when the Ambient is sated with the latter, they readily join with the former, as soon as they are received into the Body. And this is supported by the Authority even of _Bellini_, who allows, in the Beginning of his XXVIII_th Proposition_, that the _Antecedents_ to a pestilential Fever do sometimes vitiate the Spirits immediately in Quality.