The Cause of the Yellow Fever



A GREAT deal has been written respecting the yellow fever. First, with respect to its causes, whether domestic or imported. Secondly, on the mode of treating it.

What I am going to suggest in this essay is to ascertain some point to begin at, in order to arrive at the cause, and for this purpose some preliminary observations are necessary.

The yellow fever always begins in the lowest part of a populous mercantile town near the water, and continues there, without affecting the higher parts. The sphere or circuit it acts in is small, and it rages most where large quantities of new ground have been made by banking out the river, for the purpose of making wharfs.

The appearance and prevalence of the yellow fever in these places, being those where vessels arrive from the West Indies, has caused the belief that the yellow fever was imported from thence; but here are two cases acting in the same place: the one, the condition of the ground at the wharves, which being new made on the muddy and filthy bottom of the river, is different from the natural condition of the ground in the higher parts of the city, and consequently subject to produce a different kind of effluvia or vapor; the other case is the arrival of vessels from the West Indies.1

In the State of Jersey neither of these cases has taken place; no shipping arrives there, and consequently there have been no embankments for the purpose of wharfs; and the yellow fever has never broken out in Jersey. This, however, does not decide the point as to the immediate cause of the fever, but it shows that this species of fever is not common to the country in its natural state2; and, I believe the same was the case in the West Indies before embankments began for the purpose of making wharfs, which always alter the natural condition of the ground. No old history, that I know of, mentions such a disorder as the yellow fever.

A person seized with the yellow fever in an affected part of the town, and brought into the healthy part, or into the country, and among healthy persons, does not communicate it to the neighborhood, or to those immediately around him; why then are we to suppose it can be brought from the West Indies, a distance of more than a thousand miles, since we see it cannot be carried from one town to another, nor from one part of a town to another, at home? Is it in the air?3

This question on the case requires a minute examination. In the first place, the difference between air and wind is the same as between a stream of water and a standing water. A stream of water is water in motion, and wind is air in motion. In a gentle breeze the whole body of air, as far as the breeze extends, moves at the rate of seven or eight miles an hour; in a high wind, at the rate of seventy, eighty or an hundred miles an hour: when we see the shadow of a cloud gliding on the surface of the ground we see the rate at which the air moves, and it must be a good trotting horse that can keep pace with the shadow, even in a gentle breeze; consequently, a body of air that is in and over any place of the same extent as the affected part of a city may be, will, in the space of an hour, even at the moderate rate I speak of, be moved seven or eight miles to leeward; and its place, in and over the city, will be supplied by a new body of air coming from a healthy part, seven or eight miles distant the contrary way; and then on in continual succession. The disorder, therefore, is not in the air, considered in its natural state, and never stationary. This leads to another consideration of the case.

An impure effluvia, arising from some, cause in the ground, in the manner that fermenting liquors produce near their surface an effluvia that is fatal to life4, will become mixed with the air contiguous to it, and as fast as that body of air moves off it will impregnate every succeeding body of air, however pure it may be when it arrives at the place.

The result from this state of the case is, that the impure air, or vapor,

that generates the yellow fever, issues from the earth, that is, from the new made earth, or ground raised on the muddy and filthy bottom of the river; and which impregnates every fresh body of air that comes over the place, in like manner as air becomes heated when it approaches or passes over fire, or becomes offensive in smell when it approaches or passes over a body of corrupt vegetable or animal matter in a state of putrefaction.

The muddy bottom of rivers contains great quantities of impure and often inflammable air (carbureted hydrogen gas), injurious to life; and which remains entangled in the mud till let loose from thence by some accident.5 This air is produced by the dissolution and decomposition of any combustible matter falling into the water and sinking into the mud, of which the following circumstance will serve to give some explanation.

In the fall of the year that New York was evacuated (1783), General Washington had his headquarters at Mrs. Berrian's, at Rocky Hill, in Jersey, and I was there; the Congress then sat at Prince Town [Princeton]. We had several times been told that the river or creek that runs near the bottom of Rocky Hill, and over which there is a mill, might be set on fire, for that was the term the country people used; and as General Washington had a mind to try the experiment, General Lincoln, who was also there, undertook to make preparation for it against the next evening, November fifth. This was to be done, as we were told, by disturbing the mud at the bottom of the river, and holding something in a blaze, as paper or straw, a little above the surface of the water.

Colonels Humphreys and Cobb were at that time aides-de-camp of General Washington, and those two gentlemen and myself got into an argument respecting the cause. Their opinion was that, on disturbing the bottom of the river, some bituminous matter arose to the surface, which took lire when the light was put to it; I, on the contrary, supposed that a quantity of inflammable air was let loose, which ascended through the water and took fire above the surface6. Each party held to his opinion, and the next evening the experiment was to be made.

A scow had been stationed in the mill dam, and General Washington, General Lincoln and myself, and I believe Colonel Cobb (for Humphreys was sick), and three or four soldiers with poles, were put on board the scow. General Washington placed himself at one end of the scow and I at the other; each of us had a roll of cartridge paper, which we lighted and held over the water about two or three inches from the surface when the soldiers began disturbing the bottom of the river with the poles.

As General Washington sat at one end of the scow and I at the other, I could see better anything that might happen from his light than I could from my own, over which I was nearly perpendicular. When the mud at the bottom was disturbed by the poles, the air bubbles rose fast, and I saw the fire take from General Washington's light and descend from thence to the surface of the water, in a similar manner as when a lighted candle is held so as to touch the smoke of a candle just blown out the smoke will take fire and the fire will descend and light up the candle. This was demonstrative evidence that what was called setting the river on fire was setting on fire the inflammable air that arose out of the mud.

I mentioned this experiment to Mr. Rittenhouse of Philadelphia the next time I went to that city, and our opinion on the case was that the air or vapor that issued from any combustible matter (vegetable or otherwise), that underwent a dissolution and decomposition of its parts, either by fire or water in a confined place, so as not to blaze, would be inflammable and would become flame whenever it came in contact with flame.

In order to determine if this was the case, we filled up the breech of a gun barrel about five or six inches with sawdust, and the proper part with dry sand to the top, and after spiking up the touch-hole, put the breech into a smith's furnace and kept it red hot, so as to consume the sawdust; the sand of consequence would prevent any blaze.

We applied a lighted candle to the mouth of the barrel; as the first vapor that flew off would be humid, it extinguished the candle; but after applying the candle three or four times, the vapor that issued put began to flash; we then tied a bladder over the mouth of the barrel, which the vapor soon filled, and then tying a string round the neck of the bladder, above the muzzle, took the bladder off.

As we could not conveniently make experiments upon the vapor while it was in the bladder, the next operation was to get it into a phial. For this purpose, we took a phial of about three or four ounces, filled it with water, put a cork slightly into it, and introducing it into the neck of the bladder, worked the cork out, by getting hold of it through the bladder, into which the water then emptied itself, and the air in the bladder ascended into the phial; we then put the cork into the phial, and took it from the bladder. It was now in a convenient condition for experiment.

We put a lighted match into the phial, and the air or vapor in it blazed up in the manner of a chimney on fire; we extinguished it two or three times, by stopping the mouth of the phial; and putting the lighted match to it again it repeatedly took fire, till the vapor was spent, and the phial became filled with atmospheric air. These two experiments, that in which some combustible substance (branches and leaves of trees) had been decomposed by water, in the mud; and this, where the decomposition had been produced by fire, without blazing, shows that a species of air injurious to life, when taken into the lungs, may be generated from substances which, in themselves, are harmless.

It is by means similar to these that charcoal, which is made by fire without blazing, emits a vapor destructive to life. I now come to apply these cases, and the reasoning deduced therefrom, to account for the cause of the yellow fever.7

First.-The yellow fever is not a disorder produced by the climate naturally, or it would always have been here in the hot months. The climate is the same now as it was fifty or a hundred years ago; there was no yellow fever then, and it is only within the last twelve years, that such a disorder has been known in America.8

Secondly.-The low grounds on the shores of the rivers, at the cities where the yellow fever is annually generated, and continues about three months without spreading, were not subject to that disorder in their natural state, or the Indians would have forsaken them; whereas, they were the parts most frequented by the Indians in all seasons of the year, on account of fishing. The result from these cases is that the yellow fever is produced by some new circumstance not common to the country in its natural state, and the question is what is that new circumstance?

It may be said that everything done by the white people, since their settlement in the country, such as building towns, clearing lands, leveling hills, and filling valleys, is a new circumstance; but the yellow fever does not accompany any of these new circumstances. No alteration made on the dry land produces the yellow fever; we must therefore look to some other new circumstances, and we now come to those that have taken place between wet and dry, between land and water.

The shores of the rivers at New York, and also at Philadelphia, have on account of the vast increase of commerce, and for the sake of making wharfs, undergone great and rapid alterations from their natural state within a few years; and it is only in such parts of the shores where those alterations have taken place that the yellow fever has been produced. The parts where little or no alteration has been made, either on the East or North River, and which continue in their natural state, or nearly so, do not produce the yellow fever. The fact therefore points to the cause.

Besides several new streets gained from the river by embankment, there are upwards of eighty new wharfs made since the war, and the much greater part within the last ten or twelve years; the consequence of which has been that great quantities of filth or combustible matter deposited in the muddy bottom of the river contiguous to the shore, and which produced no ill effect while exposed to the air, and washed twice every twenty-four hours by the tide water, have been covered over several feet deep with new earth, and pent up, and the tide excluded. It is in these places, and in these only, that the yellow fever is produced.

Having thus shown, from the circumstances of the case, that the cause of the yellow fever is in the place where it makes its appearance, or rather, in the pernicious vapor issuing therefrom, I go to show a method of constructing wharfs, where wharfs are yet to be constructed (as on the shore on the East River at Corlder's Hook, and also on the North River) that will not occasion the yellow fever, and which may also point out a method of removing it from places already infected with it.

Instead, then, of embanking out the river and raising solid wharfs of earth on the mud bottom of the shore, the better method would be to construct wharfs on arches, built .of stone; the tide will then flow in under the arch, by which means the shore, and the muddy bottom, will be washed and kept clean, as if they were in their natural state, without wharfs.

When wharfs are constructed on the shore lengthways, that is without cutting the shore up into slips, arches can easily be turned, because arches joining each other lengthways serve as butments to each other; but when the shore is cut up into slips there can be no butments; in this case wharfs can be formed on stone pillars, or wooden piles planked over on the top.

In either of these cases, the space underneath will be commodious shelter or harbor for small boats, which can come in and go out always, except at low water, and be secure from storms and injuries. This method besides preventing the cause of the yellow fever, which I think it will, will render the wharfs more productive than the present method, because of the space preserved within the wharf.

I offer no calculation of the expense of constructing wharfs on arches or piles; but on a general view, I believe they will not be so expensive as the present method. A very great part of the expense of making solid wharfs of earth is occasioned by the carriage of materials, which will be greatly reduced by the methods here proposed, and still more so were the arches to be constructed of cast iron blocks. I suppose that one ton of cast iron blocks would go as far in the construction of an arch as twenty tons of stone.

If, by constructing wharfs in such a manner that the tide water can wash the shore and bottom of the river contiguous to the shore, as they are washed in their natural condition, the yellow fever can be prevented from generating in places where wharfs are yet to be constructed, it may point out a method of removing it, at least by degrees, from places already infected with it; which will be by opening the wharfs in two or three places in each, and letting the tide water pass through; the parts opened can be planked over, so as not to prevent the use of the wharf.

In taking up and treating this subject, I have considered it as belonging to natural philosophy, rather than medicinal art; and therefore I say nothing about the treatment of the disease after it takes place; I leave that part to those whose profession it is to study it.


June 27,1806.


  1. Due to the heroic work of Walter Reed during and after the Spanish-American War, we now know that yellow fever is carried by a particular type of mosquito, the A'edes aegypti, prevalent in the West Indies, Central America and West Africa. The disease is practically unknown in Central America today because the mosquito has been destroyed. We now know that this mosquito carries the deadly virus of yellow fever. The "new wharves" Paine speaks of was the haven for ships from the West Indies, thus the coincidence. The deadly mosquito cannot live long in our climate, but does live long enough to bite people living near the wharves.-Editor.

  2. Although New Jersey has mosquitoes they are not the kind that carry the yellow fever virus.-Editor.

  3. Yellow fever travels only where the mosquito can travel. Influenza, however, is communicated by people to each other.-Editor.

  4. This is simply a coincidence of phenomena. We now know that decaying matter is not poisonous, but since flies and mosquitoes thrive on putrified matter and since they may carry diseases people in those days associated the putrified matter with disease. However, Paine cautiously points out that he does not know if the putrified matter itself is the disease carrier. (See note 7.)-Editor.

  5. Marsh gas, "carbureted hydrogen gas," is inflammable. It is produced by decaying roots, weeds, etc. in marshes.-Editor.

  6. Paine was correct in saying that it was a gas that was inflammable.-Editor.

  7. The author does not mean to infer that the inflammable air or carbureted hydrogen gas, is the cause of the yellow fever; but that perhaps it enters into some combination with miasma generated in low grounds, which produces the disease.-Author

  8. Such extensive trade with the West Indies had not taken place previous to the period during which the article was written.-Editor.