Washington Apr. 30. 06.
It is now some time since I recieved through the channel of mr Appleton, our Consul at Leghorn, your letter of May 15. and your book Dei provvedimenti Annonarj for which I pray you to accept my thanks. the subject of the latter is among the most interesting to man; it is luminously treated, & cannot fail to have effect when the state of the world shall leave legislators the necessary leisure to attend to the amelioration of the condition of those committed to their charge. but during the heavy afflictions under which Europe has for some time suffered, it is not to be wondered at, if the correction of those antient errors & abuses, which philosophy has so clearly exposed, should give place to evils more pressing & which engross all the attention of governments. wars, volcanos, famine & disease have in different portions of that country been committing their combined ravages on the race of man. we are happy in our distance from the scenes of so much trouble. war, volcanoes, famine, are unknown to us; but we have not been free from the visitations of disease. within the last 10. years the fever which is the subject of your letter, or one bearing resemblance to it, under the name of Yellow fever, has, at times, afflicted our populous towns. at first the numbers siesed in the same quarters of the towns, gave it the appearance & the reputation of being infectious. but further experience has produced facts inconsistent with that character of disease. it is found to be strictly local, circumscribed by well defined lines, in close built cities, in their most crowded parts on the water edge & of tide waters only. it has never commenced till Autumn, nor failed to disappear compleatly with the first frosts, and sometimes with heavy rains. to contract it you must go into the infected quarter. out of that it is incommunicable by the contact either of persons or things, & therefore, within that, is presumeably not communicated by contact. never was there an instance of it’s being communicated in the country, altho hundreds have taken it in the cities, have gone to their families or friends in the country & have there been nursed, died, & buried. hitherto it has been confined to the tide waters between the latitudes of New York & Alexandria, comprehending about two degrees. altho’ these facts are now palpable to every unprejudiced observer, yet the disposition in men to schismatize & dispute, has produced some contradiction to them. this is countenanced by first giving arbitrary & incorrect definitions of Yellow fever, which comprehend other species of fever, long known through all seasons & places, & concerning which these facts are not true. but of that singular fever which was never known to us till 1795 & has been so mortal to natives as well as strangers in a few of our cities, they are unquestionably true; and they decide it to be not injurious, but merely endemial and autumnal. you will be the best judge whether these characters agree with those of the fever which is the subject of your letter so as to decide them to be the same or different. among the advantages to be derived from the progress of science, I am happy to observe that chemistry promises a more speedy & effectual mode of disinfecting the air of contagious houses & vessels than the oppressive practice of Quarentine a barbarous continuation of antient ignorance & habit. M. de Morveau in his book on this subject authorizes us to entertain this hope. Accept, Sir, my friendly salutations and assurances of great esteem & respect.
DLC: Papers of Thomas Jefferson.