William Dunbar to the American Philosophical Society, via Thomas Jefferson, read December 18, 1801.
Transactions of the American Philosophical Society, Vol. IV. Philadelphia, 1804.
This report, with several other missives and reports written by Dunbar, were forwarded by Jefferson to the American Philosphical Society, where they were read before the Society and later published in the Transactions of the Philosophical Society of America in 1804. Dunbar's detailed descriptions of the weather and growing conditions in Lousiana were sure to interest Jefferson.
TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY, &c. No. IX. METEOROLOGICAL OBSERVATIONS,
MADE by William Dunbar, Esq, at the Forest, four miles east of the River Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) , in Lat. 31° 28' North, and in Long. 91° 30' west of Greenwich, for the year 1800; with remarks on the state of the winds, weather, vegetation, &c. calculated to give some idea of the climate of that country.
Natchez Maps: Antoine-Simon Le Page du Pratz (1763) , Aug, 22, 1801,Read December 18th, 1801. MONTHLY RECAPITULATION. [Ed. note: Please see the image of the chart that fills up this page.]
REMARKS transcribed from the general daily Journal. JANUARY.
THIS month has been attended with more regular continued cold than is usual in this climate, with a smaller proportion of rain, which fell in moderate quantities on 7 or 8 different days; on the 31st. we were presented with a beautiful appearance. As the rain and sleet fell, the branches of trees were enveloped in a thin sheet of ice, and from every minute protuberance or angle depended an elegant christalization, which altogether produced an enchanting effect, giving to the trees the appearance of the most resplendent blossoms. Many large limbs were broken down with the weight of the ice.
FEBRUARY. 2d. This morning the ground is covered with snow, and the trees beautifully spangled with ice. At 10 o'clock the snow begins to melt away, although the sun is yet veiled in clouds. The snow to the depth of two inches is speedily thawed, in exposed situations; but remains all day on dry grass, chips and other bad conductors of heat, to the north of buildings, trees &c. but no where on the bare ground.
3d. This morning the ground is white with snow, and the trees compleatly glazed. One would suppose himself rather in Canada than in lat. 31 °. — The sun peeps out, and a moment is granted to admire the most enchanting of pictures—The eye is dazzled with the prospect of myriads of gems, beautiful beyond imagination, with which the whole forest is decked, reflecting a combination of the most vivid colours from the facets of the icy chrystalizations—but another moment, and all is dissolved. From the dreary depth of winter we emerge at once to the enjoyment of the delicious softness of a morning in May.
MARCH. 5th. Elm, Buckeye (horse–chesnut) and spice–wood begin to bud.
10th. Planted corn and rice.
12th. Dogwood displays its beautiful blossoms, as also the red–bud.
18th. Trees in general begin to shew their buds and blossoms, excepting the nut–bearing kinds, linden &c.—Planted cotton the 22d.
APRIL. Continue to plant cotton daily. 7th. Good pasturage in the wood–land.
10th. Peas ripen—Hickory, Walnut and Chinquepin begin to bud.—11th. Abundance of pasture in the wood–land. 13th. Garden–peas gathered to eat. 15th. Roses blow. 25th. Windsor–beans and Artichokes ripe.–Strawberries ripe since the 12th.
MAY. 5th. Irish potatoes begin to be fit to gather. 10th. Black Mulberry ripe. Gathered ripe turnip and cabbage seed. 12th. French beans fit for use.—17th. Rye and wheat fit to reap. The present is one of the most delightful months of the year, being free from sudden storms, and agreeably temperate; it is generally one of the driest months, but the present is an exception to that rule.
JUNE. 12th. Cotton begins to blossom and the weather becomes hotter than usual at this season. When the Thermometer is at 96°. under a gallery compleatly shaded, though exposed in some degree to the influence of reflection from the bare surface of the earth, if in such circumstances it be removed into a deep shade, under lofty trees, at 3 hours P. M. it will fall to 91 or 92°. If suspended to a tree exposed to the full influence of the sun–beams it rises quickly to 121°. –it perhaps might have risen higher, but being unwilling to risk the bursting of the Thermometer, as it is graduated only to 125°, I removed it without farther trial. In a cellar under the house, dug 4 1/2. feet into the, ground, the Thermometer stood at 72°.—15th. Tender Indian corn fit to use.
JULY. This month yields a good deal of rain,—it begins to be showery about the commencement of the month, sometimes before; had not the course of providence thus ordered it, the present and succeeding months would have become intolerable from heat, and a period would have been put to vegetation; but refreshing and cooling showers, which are almost periodical at this season, falling daily in some one part or more of an extent of 20 or 30 square miles, render the mean temperature of these two months much less than might have been expected from that of the preceeding month of June, which is not unfrequently the hottest month of the year, though in the present it is inferior to both the succeeding months; but it is remarkable that much less rain fell than usual during the month of August, the natural consequence of which is an increase of temperature. I have anticipated the last observation respecting the succeeding month as having an immediate connection with the foregoing remarks.
AUGUST. From the unusual heat of the season, the cotton harvest is found advanced ten days earlier than in former years, and a commencement was made on the 18th. to collect our valuable staple commodity. In the beginning of the season while the cotton is not yet abundant, a good labourer collects from 50 to 80 pounds in the seed, but as the crop advances to greater maturity and abundance, the task of able men and women may be estimated from 80 to 140 1b. which yields one quarter clean cotton fit to be packed for market, when passed through the ginning mill. The harvesting season may continue from 3 to 4 months; from which may be formed some estimate of this very productive branch of agriculture.
This month is attended with a good deal of rain and introduces the powerful influence of a second spring season upon all vegetating bodies; the two grand agents, heat and moisture, being now found in that due degree most favourable to rapid
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vegetation. Seeds and grain which have been committed to the soil, during the last and present month, start mw life and their orgahic parts are developed with a vigour unknown to other climes. This is the propitious season for preparing and perfecting the productions of the kitchen–garden, which are to supply us with culinary herbs and roots, during the wirner and spring season.
OCTOBER. The present is the most agreeable month of the year; its temperature is mild and refreshing, occupying the due medium between the extremes of heat and cold. It generally sets in fair during the first week or 10 days of the month, which continues for 6, 7 or more weeks—–Nothing can be more favourable than this enchanting season for the restoration of the health of the valetudinarian, who may have suffered from the autumnal intermittent, which generally attacks strangers, soon after the river retires within its banks, about the end of June or beginning of July, and which by the way does not extend its influence beyond 4, 5 or 6 miles from the river swamps, tho' probably when our forests, shall be cut down, this annual visitant of our (otherwise) salubrious climate, will penetrate farther into the interior. The cotton planter too has. cause to admire the dispensations of Providence, which facilitate the collecting a most valuable crop, which by an opposite order of the seasons must be totally lost.
NOVEMBER. The first half and sometimes the whole of this month continues remarkably fine; the present has been particularly so, a few drops of rain having fallen only the first day: about the 22d. and 23d. a north–west wind caused the thermometer to sink below the freezing point, but it presently ascended again and the weather continued mild to the end of the month, the thermometer standing at mid–day from 60 to 70°.—The ewes begin to drop their lambs about the commencement of the month, and continue for three months.
DECEMBER. The winter now being set in, the weather becomes variable, and a considerable quantity of rain generally falls in the course of the month. This year upon the whole has yielded less rain than the year 1799 and the present month has produced less than the same month of the last year by 2.78 inches. This month has been particularly remarkable for a degree of cold hitherto unexampled in the history of this country–on the morning of the 12th. the thermometer was found sunken to +12°; on that day it did not rise above the freezing point, and next morning was at 17°—on that day it rose to 49°; and both before and after was up to 72° —Cows begin to calve about the commencement of the month and continue calving for 3 or 4 months. Mares are generally a month later in bringing their young.
GENERAL REMARKS respecting the winds, weather, &c. IT is with us a general remark, that of late years the summers have become hotter and the winters colder than formerly. Orange trees and other tender exotics have suffered much more in the neighbourhood of New Orleans within these 4 or 5 years than before that period; the sugar cane also has been so much injured by the severity of the frosts of the two last winters, as greatly to discourage the planters, whose crops, in many instances, have fallen to one third or less of their expectations. In former years I have observed the mercury of the thermometer not to fall lower than 26 or 27°, but for a few years past, it has generally once or twice in the winter fallen as low as from 17 to 20°. and on the 12th. of December 1800 as above noticed it was found sunken to 12°. which has hitherto no parrallel in this climate, indicating a degree of cold which in any country would be considered considerable, and probably may never be again produced by natural means in lat. 31 1/2°.
As this apparent alteration of climate has been remarked only for a few years and cannot be traced up to any visible natural or artificial change of sufficient magnitude, it would be in vain to search for its physical cause. Doctor Williamson and others have endeavoured to show that clearing, draining and cultivation, extended over the face of a continent, must produce the double effect of a relaxation of the rigours of winter, and an abatement of the heats of summer; the former is probably more evident than the latter, but admitting the demonstration to be conclusive, I would enquire whether a partial clearing extending 30 or 40 miles square, may not be expected to produce a contrary effect by admitting with full liberty, the sunbeams upon the discovered surface of the earth in summer, and promoting during winter a free circulation of cold northern air.
The winds of this country are extremely variable in the winter season, seldom blowing above three days successively from the same point; the north–west wind brings us the severest cold. It may be considered as a general rule during winter, that all winds blowing from the east of the meridian bring rain, and those from the west dry weather; the east and south east winds are most abundantly charged with moisture, as the opposite points are always the driest; the north–east wind during this season is moist chilly and disagreeable, but seldom prevails for any length of time: the north–wind brings (though rarely) sleet or snow.–After 2, 3 or 4 days of damp cloudy or rainy weather, it suddenly clears up with a cold north–west wind, which blows frequently with great force during the first and sometimes part of the second day of the change, the nights being generally calm; after a like period of fair weather, of which the two first days are clear and freezing, and the other two fine mild and agreeable with a morning's hoar frost, it revolve again into the same circle of damp and rainy weather. This may be considered as the general revolution of the winter season, but with many exceptions. The frequent and rapid changes in the state of the weather, during the winter in this climate furnish an excellent opportunity of verifying the vulgar opinion of the moon's pretended influence at her conjunctions, oppositions and quadrature but truth compels me
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to say (what probably may be said of many similar persuasions) that after a continued and scrupulous attention to this object, I have not discovered any such regularity of coincidence, which might justify the reverence with which those traditional maxims are at this day received by all these whose minds are not expanded by the lights of philosophy.
With the month of February our spring season may be said to commence and southerly winds prevail, as if propitious nature was inclined to facilitate the operations of the husbandman, by carrying off the superabundant moisture with which the surface of the earth is drenched after the winter rains. This salutary effect is much more apparent on the flat lands of lower Louisiana than with us. Those regular gales are also peculiarly favourable in facilitating the ascent of the commercial boats, which at this season, with commencement of the annual inundation, perform their yearly voyage to the Spanish settlements in the higher parts of Louisiana.
As the spring and summer advance, the winds blow chiefly from between S. E. and S. W. with variations from all parts of the compass. During the hot season, the winds are frequently remarked to follow the progress of the sun, being found at N. E. or East in the morning and shifting round, die away in the evening at S. S. W.—The summer evenings are generally still until between 8 and 9 o'clock when a fine cool zephyr sets in, from the West or S. W.—It has been said that in the lower parts of the territory near the Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) this refreshing nocturnal breeze blows from the East: hitherto correct observations have not been sufficiently multiplied in various parts of the territory to furnish a satisfactory account of this object. The month of June and about one half of July compose the hottest season of the year. Daily refreshing showers of rain commence in July and continue through August, which diminish the excessive degree of heat that otherwise must prevail at this season. The weather continues showery through September, but in October it settles fine, and there is yearly almost without exception 6 or 7 weeks of the most delightful season imaginable, the mean temperature being from 65 to 70°. with variable winds from all points of the compass.
Before the close of November we are reminded of the approach of winter by a few cold mornings and evenings and sometimes nipping frosts, which exhibit their destructive power, first, in the values by killing tender plants, while those on the adjoining hills retain sometime longer their bloom and verdure. This effect is to be accounted for by the greater specific gravity of the condensed freezing air, which runs off on all sides from elevated situations into the nearest values, there forming a mass of great extent, while the hills are supplied with air less dense and warmer from a superior stratum of the atmosphere. The infiuence of this cause is so great at the first approaches of winter that a difference of 10°. of Farenheit's scale has been noted at the short interval of 3 miles in the direction of East and West; one position overlooking the great valley of the Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) 30 miles wide, while the other was in the interior, environed by forests. On the morning of the 13th, November 1799 the thermometer stood in the first situation at 42°. and in the latter at 32°.
We are told that at Benares in the East Indies lat. 23 1/2°. ice is produced by natural agents artificially brought together, sufficient for the purposes of luxury. Large excavations are dug in an extensive plain, into which the condensed freezing air is collected in a considerable mass, but which probably might have formed upon the plain a stratum of a few inches only, and consequently must have been speedily mollified by the transpiration of the earth, without producing any effect; but being thus accumulated into a body of considerable magnitude it is found that in the stillness of a fine night, water contained in shallow unglazed vessels, placed upon a stratum of about a foot in thickness of some imperfect conductor of heat, such as the stalks of Maize &c. on the bottom of those excavations, is partially or totally converted into ice, according to the degree of temperature of the atmosphere, while perhaps the slightest hoar–frost is not perceptible on the natural surface–perfect calmness is essential to the success of this curious experiment; a moderate circulation of air counteracts the laws of specific gravity, and restores the equilibrium of the caloric in the adjacent strata of the atmosphere.
The North and N. W. wind blows often with some severity before the close of the month of November, shifting to the East of the meridian with fogs and some rain: the fogs being more remarkable in lower Louisiana and adjoining to the great valley of the Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) . The winter now sets in with the month of December and its duration may be estimated at two months, although during its whole course, when the wind continues for some time at S. and S. W. we enjoy a very agreeable mild and some times warm temperature, the thermometer often rising to 75°. or more. Hence it follows that our winter climate depends altogether upon the course of the winds. South and S. W. winds involve us within a tropical atmosphere corrected however by the accessions of cold which we have received already from the North, and which produces a most agreeable spring or mild summer temperature; the productions of the garden now vegetate with vigour and if long, enough continued the fields assume a verdant hue–a mild fall and moderate winter some times permit us to gather from our gardens at Christmas, green peas and other summer productions. But when on the other hand the winds blow from the N. W. and North we are at once plunged into the rigors of a Northern winter; hence it is that tender shrubs and plants are frequently destroyed here which might be expected to withstand a more Northern clime. The human body also is extremely susceptible of the sudden transitions which naturally suggests the idea, that frequent pleuritic and inflammatory diseases must be the natural attendants of our variable winter climate, but experience demonstrate the contrary. Probably the relaxation which the body undergoes during, the extreme heats of summer diminishes the oxygenation of the blood and consequently renders it less susceptible of inflammation.
August and September are called the hurricane months, and I believe there never happens a hurricane of great extent and duration at any other season, and this seldom reaches much higher than New Orleans, sweeping along the sea coast. Storms, hurricanes, whirlwinds or tornados of small extent and very short duration, happen at any season and from all points of the compass. We ought perhaps to except the months of May and October, least of all subject to sudden changes and which
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upon the whole are the most agreeable months of the year. Sudden gusts or storms of wind and rain generally proceed from N. or N. N. E. and their violence is only of a few minutes duration, although in that short time, it frequently happens that trees are torn up by the roots or snapt short off, houses stript of their covering, fences thrown down and crops greatly damaged and blown about in the air.—Since I have resided in this country, two or three hurricanes only, of great magnitude, have ravaged New Orleans and its vicinity. Two of them burst forth in the months of August of the years 1779 and 1780; I was at New Orleans during the first of those two. More than half of the town was stript of its covering, many houses thrown down in town and country, no ship or vessel of any kind was to be seen on the river next morning. The river which at this season is low was forced over its banks, and the crops which were not yet collected, disappeared from the face of the earth. The forests for some leagues above and below New Orleans assumed the dreary appearance of winter, the woods over large tracts were laid flat with the ground, and it became impossibLe to traverse the forests, but with immense labour on account of the multitude of logs, limbs and branches with which the earth was every were strewed within the extent of the hurricane; which might be estimated at about 12 miles due North and South, New Orleans being in the centre of its passage. The partial hurricanes which frequently traverse this territory do not merit the name and ought rather be called whirlwinds, which seldom last above 5 to 10 minutes, occupying a narrow vein from 50 to 500 feet in width; whereas that which I witnessed at New Orleans was of some hours duration; it continued blowing from the East or. S. E. for two or three hours with undescribable impetuosity, after which succeeded all at once a most profound and awful calm, so inconceivably terrific that the stoutest heart stood appaled and could not look upon it without feeling a secret horror,as if nature were preparing to resolve herself again into chaos. The body became totally unelastic and a disposition was felt to abandon oneself prostrate upon the ground as if despair alone at that moment, could find abode in the human mind, entirely divested of all energy. How is this extraordinary effect to be ac–
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counted for? It is generally believed by philosophers, that hurricanes and perhaps the gentlest zephyrs are connected with electrical phænomina, may we then be permitted to suppose that by the violent operation of natural agents (of which we can form no conception) the electric fluid has been in a manner abstracted from the central parts of the hurricane (which we may consider as a vortex) and a species of vacuum formed with respect to the electric fluid–hence that otherwise unaccountable relaxation and dejection of spirits, similar to (though infinitely exceeding) what has been observed of the influence of the sirocco wind in Naples and Sicily upon the human body and mind, no perceptible signs of electricity being discoverable in the atmosphere during the time of its blowing.–Happily the wind was arrested but for a short time, by this horrid state of suspence, for in 5 or 6 minutes, perhaps less, the hurricane began to blow from the opposite point of the compass and very speedily regained a degree of fury and impetuosity equal if not superior to what it had before possessed. Floating bodies, which had been driven up the stream with vast rapidity against the natural course of the river, now descended with a velocity of which the astonished eye could form no estimate, it rather resembled the passage of a winged inhabitant of the air than that of a body born upon the more sluggish element of water. Vessels were left upon dry land or dashed in pieces against the shores. An American armed ship being overset was precipitated into the ocean and never more heard of; the officers and men were chiefly saved by leaping ashore, sometimes by the assistance of rafts and logs of timber, watching the opportunity of the vessel impinging against the bank as she darted from side to side of the river, hurled along by the ungovernable fury of the torrent. From every information I could procure, I believe the center of the hurricane passed over the city of New Orleans, the general progress of its course being at that time from about N. E. to S. W. and as its first fury was felt in the direction of S. E. nearly, and ended about N. W. it is evident that the circular course of the vortex followed that of the sun's apparent diurnal motion.—It is probable that if similar observations are made upon all hurricanes, tornados and whirlwinds they will be founs
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universally to consist of a vortex with a central spot in a state of profound calm, which spot will probably be greater or less according to the magnitude of the vortex.
No circumstance occurred to me which might justify the hypothesis of the celebrated Franklin who supposed the center of a whirlwind or waterspout to be a true vacuum capable of elevating water to the height of 30 or more feet. It is by no means decided that those two phænomena are of the same species. Whirlwinds are always perpendicular to the horizon and are, I believe, never stationary: an intelligent friend of mine once saw (what he supposed to be) a waterspout descend from a low cloud into the Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) , it made a very considerable angle with the perpendicular and its inferior extremity remained fixed to one spot during the whole time of its ap pearance, the very gentle progress of the cloud seemed to prolong the spout, so that at length it separated into two parts, the interior division, which was by much the shortest, falling into the Mississippi Maps: John Mitchell (1755) Antoine-Simon Le Page du Pratz (1763) Thomas Hutchins (1778) Aaron Arrowsmith (1811) Aaron Arrowsmith (1802) , and the superior slowly ascending until it became united to the cloud.