The matter which produced the fever in both these cases, had nothing specific in it. It acted in the same manner that the exhalation from any other putrid matters would have done in a highly concentrated state. In a letter from Dr. Senter of Newport, dated January 7th, 1794, I find the following fact, which I shall communicate in his own words. It is introduced to support the principle, that the yellow fever does not spread by contagion. "This place (says the doctor) has traded formerly very much to the West-India islands, and more or less of our people have died there every season, when the disease prevails in those parts. Clothes of these unfortunate people have been repeatedly brought home to their friends, without any accident happening to them." I feel with my reader the fatigue of this long detail of facts, and equal impatience with him to proceed to the history of the treatment of the fever; but I must beg leave to detain him a little longer from that part of the work, while I resume the subject of the origin of the fever. It is an interesting question, as it involves in it the means of preventing the return of the disease, and thereby of saving the lives of thousands of our citizens. Soon after the fever left the city, the governor of the state addressed a letter to the college of physicians, requesting to know their opinion of its origin; if imported, from what _place_, at what _time_, and in what _manner_. The design of this inquiry was to procure such information as was proper to lay before the legislature, in order to improve the laws for preventing the importation or generation of infectious diseases, or to enact new ones, if necessary for that purpose. To the governor's letter the college of physicians sent the following answer: "SIR, "It has not been from a want of respect to yourself, nor from inattention to the subject, that your letter of the 30th ult. was not sooner answered; but the importance of the questions proposed has made it necessary for us to devote a considerable portion of time and attention to the subject, in order to arrive at a safe and just conclusion. "No instance has ever occurred of the disease called the _yellow fever_ having been generated in this city, or in any other parts of the United States, as far as we know; but there have been frequent instances of its having been imported, not only into this, but into other parts of North-America, and prevailing there for a certain period of time; and from the rise, progress, and nature of the malignant fever, which began to prevail here about the beginning of last August, and extended itself gradually over a great part of the city, we are of opinion that this disease was imported into Philadelphia, by some of the vessels which arrived in the port after the middle of July. This opinion we are further confirmed in by various accounts we have received from unquestionable authorities. "Signed, by order of the college of physicians,