I inclose for your perusal a letter from Dr. Rush, asking the favor of you to return it. on the question Whether the Yellow fever is infectious, or endemic, the Medical faculty is divided into parties, and it certainly is not the office of the public functionaries to denounce either party as the Doctr. proposes. yet, so far as they are called on to act, they must form for themselves an opinion to act on. in the early history of this disease, I did suppose it to be infectious. not reading any of the party papers on either side, I continued in this supposition, until the fever at Alexandria brought facts under my own eye, as it were, proving it could not be communicated but in a local atmosphere, pretty exactly circumscribed. with the composition of this atmosphere we are unacquainted: we know only that it is generated near the water side, in close built cities, under warm climates. according to the rules of philosophising, where one sufficient cause for an effect is known, it is not within the economy of nature to employ two. if local atmosphere suffices to produce the fever, miasmata from a human subject are not necessary, and probably do not enter into the cause. still it is not within my province to decide the question: but as it may be within yours to require the performance of Quarentine or not, I execute a private duty in submitting Doctr. Rush’s letter to your consideration. but on this subject ‘nil mihi rescribas, attamen ipse veni.’ Accept for yourself & mrs Page affectionate & respectful salutations.