I had the honor of your letter of a late date covering one from Dr Tufts, which has furnished me with some very useful facts; & for which I must beg leave to communicate to you & to him my most respectful Acknowlegements—

If I could obtain similar facts from the year 1700, I should be well fortified with American proof of the general principles that govern Epidemics; as it is, I have proof enough. I find it a general fact that the plague & other pestilential diseases are preceded by an Epidemic Catarrh. It has happened several times, in the present century; & what is singular, several instances occur, (tho I am not prepared to say all,) in which that Catarrh has appeared in America the year preceding its prevalence in Europe—its progress has been from West to East.

But no principle is better established by facts than that all great epidemics depend on essential changes in the properties of the air, independent of local causes. This will be proved beyond controversy. It will also be made very probable that the great cause of such changes, is the action of subterranean heat—producing invisible vapor or exhalations from the earth; for all violent pestilences from the days of Thucydides to this hour, have been attended with violent earthquakes & eruptions of Volcanoes, & the same principle probably which destroys man & cattle on the surface of the earth, proves fatal to the fish in the ocean & in rivers.—

Be assured Sir, of my best wishes for your public property & private happiness, & believe me with the highest respect / your Obedient & very / humble Servt