Query VII.[ 122 ]
A NOTICE of all what can increase the progress of human knowledge?
Under the latitude of this query, I will presume it not improper nor unacceptable to furnish some data for estimating the climate of Virginia. Journals of observations on the quantity of rain, and degree of heat, being lengthy, confused, and too minute to produce general and distinct ideas, I have taken five years observations, to wit, from 1772 to 1777, made in Williamsburgh and its neighbourhood, have reduced them to an average for every month in the year, and stated those averages in the following table, adding an analytical view of the winds during the same period.
[ Tip-in 17, Page 1 ]
Memorandum of observations made by Genl Dearborn
In the month of August 1801 I carefully examined the temperature of my well water in the district of maine, and found it at 52 degrees of Fahrenheit's thermometer–
the depth of the well is 28 feet; the depth of the water at this time was 4 feet; the latitude of the place is 44 22 N. Long. about 69 40 W.
In Sept. 1802, I examined with the same instrument, and with equal care, the temperature of the well water where I live on the Capitol hill, and found it at 59° of Fahrenheit. This well is upwards of 40 feet in depth, and had at the time about 7 or 8 feet of water.
My well in Maine is an open draw well without a pump. the well on the Capitol hill has a pump is close covered.
The temperature of the water of Kennebeck river, the latter part of August, was 72½ by Fahrenheit.
[ Tip-in 18, Page 1 ]
|1789||Oct. 1.||ice||.snow birds.||spoiled tobacco on the scaffold|
|`1792||Sept. 21||none||. none .||tobacco destroyed totally, out of Greenbelt|
|`1808||Sept. 27 -||none||none||Tob. except in Green belt, untouched.|
|1816||Oct. 7.||thin ice||. snow birds.||late corn spoiled; all safe in G. belt|
|`1823.||Sept. 29 -||none||.none .||Green belt unaffected: pumpkin vine frozen.|
[ 123 ]
|Fall of rain, c. in inches.||Least greatest daily heat by Farenheit's thermometer.||WINDS|
|N.||N. E.||E.||S. E.||S.||S. W.||W.||N. W.||Total|
|Jan.||3.192||38½ to 44||73||47||32||10||11||78||40||46||337|
|Total.||47.038||8 A.M. 4 P.M.||611||548||521||223||109||926||351||409||3698|
[ 124 ]
The rains of every month, (as of January for instance) through the whole period of years, were added separately, and an average drawn from them. The coolest and warmest point of the same day in each year of the period were added separately, and an average of the greatest cold and greatest heat of that day, was formed. From the averages of every day in the month, a general average for the whole month was formed. The point from which the wind blew was observed two or three times in every day. These observations, in the month of January for instance, through the whole period amounted to 337. At 73 of these, the wind was from the North; at 47, from the Northeast, c. So that it will be easy to see in what proportion each wind usually prevails in each month: or, taking the whole year, the total of observations through the whole period having been 3698, it will be observed that 611 of them were from the North, 558 from the North-east, c.
Though by this table it appears we have on an average 47 inches of rain annually, which is considerably more than usually falls in Europe, yet from the information I have collected, I suppose we have a much greater proportion of sunshine here than there. Perhaps it will be found there are twice as [ 125 ]
In an extensive country, it will of course be expected that the climate is not the same in all its parts. It is remarkable that, proceeding on the same parallel of latitude westwardly, the climate becomes colder in like manner as when you proceed northwardly. This continues to be the case till you attain the summit of the Alleghaney, which is the highest land between the ocean and the Missisipi. From thence, descending in the same latitude to the Missisipi, the change reverses; and, if we may believe travellers, it becomes warmer there than it is in the same latitude on the sea side. Their testimony is strengthened by the vegetables and animals which subsist and multiply there naturally, and do not on our sea coast. Thus Catalpas grow spontaneously on the Missisipi, as far as the latitude of 37°. and reeds as far as 38°. Perroquets even winter on the Sioto, in the 39th degree of latitude. In the summer of 1779, when the thermometer was at 90°. at Monticello, and 96 at Williamsburgh, it was 110°. at Kaskaskia. Perhaps the mountain, which overhangs this village on the [ 126 ][ 127 ]
But a more remarkable difference is in the winds which prevail in the different parts of the country. The following table exhibits a comparative view of the winds prevailing at Williamsburgh, and at Monticello. It is formed by reducing nine months observations at Monticello to four principal points, to wit, the North-east, South-east, South-west, and North-west; these points being perpendicular to, or parallel with our coast, mountains and rivers: and by reducing, in like manner, an equal number of observations, to wit, 421. from the preceding table of winds at Williamsburgh, taking them proportionably from every point.
By this it may be seen that the South-west wind prevails equally at both places; that [ 128 ]
Going out into the open air, in the temperate, and in the warm months of the year, we often meet with bodies of warm air, which, passing by us in two or three seconds, do not afford time to the most sensible thermometer to seize their temperature. Judging from my feelings only, I think they approach the ordinary heat of the human body. [ 129 ]
The variation in the weight of our atmosphere, as indicated by the barometer, is not equal to two inches of mercury. During twelve months observation at Williamsburgh, the extremes were 29, and 30.86 inches, the [ 130 ]
Our changes from heat to cold, and cold to heat, are very sudden and great. The mercury in Farenheit's thermometer has been known to descend from 92°. to 47°. in thirteen hours.
It is taken for granted, that the preceding table of averaged heat will not give a false idea on this subject, as it proposes to state only the ordinary heat and cold of each month, and not those which are extraordinary. At Williamsburgh in August 1766, the mercury in Farenheit's thermometer was at 98°. corresponding with 29⅓ of Reaumur. René Antoine Ferchault de Reaumur (1683-1757), French naturalist who invented a thermometer with a scale in which 0° was the freezing point and 80° the boiling point of water. At the same place in January 1780, it was at 6°. corresponding with 11½ below 0. of Reaumur. I believe * these may be [ 131 ][ 132 ]
The access of frost in autumn, and its recess in the spring, do not seem to depend merely on the degree of cold; much less on the air's being at the freezing point. White frosts are frequent when the thermometer is at 47°. have killed young plants of Indian corn at 48°. and have been known at 54°. Black frost, and even ice, have been produced at 38½°, which is 6½ degrees above the freezing point. That other circumstances must be combined with the cold to produce frost, is evident from this also, that on the higher parts of mountains, where it is absolutely colder than in the plains on which they stand, frosts do not appear so early by a considerable space of time in autumn, and go off sooner in the spring, than in the plains. I have known frosts so severe as to kill the hiccory trees round about Monticello, and yet not injure the tender fruit blossoms then in bloom on the top and higher parts of the mountain; and in the [ Tip-in 19, Page 1 ]
Notes on Virginia. Qu. VII. pa. 132 l.5. subjoin this note.
* The following observations on heat and cold, as they affect the animal body, may not be unacceptable to those who have not paid particular attention to the subject.
The living body (not like the dead one, which assumes the temperature of the surrounding atmosphere) maintains within itself a steady heat of about 96°. of Fareheit's thermometer, varying little with the ordinary variations of the atmosphere. this heat is principally supplied by respiration. the vital air, or oxygen of the atmospheric fluid inhaled, is separated by the lungs from the azotic carbonic parts, and is absorbed by them; the caloric is disengaged, diffused thro' the mass of the body, and absorbed from the skin by the external air coming into contact with it. if the external air is of a high temperature, it does not take up the superfluous heat of the body fast enough, and we complain of too much heat: if it is very cold, it absorbs the heat too fast, produces the sensation of cold. to remedy this, we interpose a covering, which acting as a strainer, lets less air come into contact with the body, and checks the escape of the vital heat. as the atmospheric air becomes colder, more or thicker coverings are used, till no more than the requisite portion of heat is conducted from the body. as it would be inconvenient in the day to be burthened with a mass of clothing entirely equivalent to great degrees of cold, we have resort to fires and warm rooms to correct the state of the atmosphere, as a supplement to our clothing. if we have not the opportunity, and the cold is excessive, the thinner parts, as the ear, the nose, the fingers and toes lose heat till they freeze, and, if the cold be sufficient, the whole body is reduced in heat, till death ensues: as sailors experience who escape from shipwreck, in winter storms, on desert shores, where no fire can be found.[ Tip-in 19, Page 2 ]
Of the substances we use for covering, linen seems the openest strainer for admission of air to the body, and the most copious conductor of heat from it; and is therefore considered as a cool clothing. cotton obstructs still more the passage of both fluids; and wool more than cotton: it is called therefore a worse conductor of heat, and warmer clothing. next to this are the furs, and the most impermeable of all for heat and air are feathers and down, and especially the down of the Eider duck. (Anas mollissima.) hence the insensibility to cold of the beasts with shaggy hair, or fine fur, and of the birds in proportion as they are provided with down and soft feathers, as the swan, goose, and duck.
Among the substances which, as being bad conductors of heat, foment and warm the animal body, are the leaves of the Espeletia Frailexon, a plant newly discovered by the great naturalist and traveller Baron Humboldt, on the mountains of S. America, at the height of 2450. toises above the sea. these leaves being furnished abundantly with a soft down, restore immediately to their due warmth the hands, feet, or other members benumbed with cold; and collected as a bed, protect from death the Indian benighted in those regions of extreme cold. the same scientific traveller, by analysis of the air, at different heights on the mountain of Chimborazo which he ascended to the height of 3036 toises (546 toises higher than had ever been done by man before, and within 224 toises of it's top) found that the oxygen being specifically heavier than the azotic part of the atmosphere, it's proportion lessened in that ascent 27. or 28. to 19½ hundredth parts. The same circumstance had been before observed by Saussure, Pini Rebout on the high mountains of Europe, and must be among the principal causes of the degree in which the animal body is affected with cold in situations more or less elevated.[ Tip-in 19, Page 3 ]
In addition to the effect of vital air, as the vehicle of animal heat, we may note that it is also the immediate cause, or primum mobile of life. for, entering by respiration into the air cells of the lungs, divided from those of the blood but by a thin membrane, it infuses thro' that a stimulus into the blood, which, acting on the irritable fibres of the heart, excites mechanically the action and reaction of that muscle. by these the blood is propelled, and received again in a course of constant circulation and vital action communicated and maintained thro' all the system. intercept vital air from the lungs, the action of the heart ceases for want of stimulus, the current of the blood, unaided, yields to the resistance of it's channels, all the vital motions are suspended, body becomes an inanimated lump of matter.
[ 133 ]
The weavil has not yet ascended the high mountains.
A more satisfactory estimate of our climate to some, may perhaps be formed, by noting the plants which grow here, subject however to be killed by our severest colds. These are the fig, pomegranate, artichoke, [ 134 ]
A change in our climate however is taking place very sensibly. Both heats and colds are become much more moderate within the memory even of the middle-aged. Snows are less frequent and less deep. They do not often lie, below the mountains, more than one, two, or three days, and very rarely a week. They are remembered to have been formerly frequent, deep, and of long continuance. The elderly inform me the earth used to be covered with snow about three months in every year. The rivers, which then seldom failed to freeze over in the course of the winter, scarcely ever do so now. This change has produced an unfortunate fluctuation between heat and cold, in the spring of the year, which is very fatal to fruits. From the year 1741 to 1769, an interval of twenty-eight years, there was no instance of fruit [ 135 ]
Having had occasion to mention the particular situation of Monticello for other purposes, I will just take notice that its elevation affords an opportunity of seeing a phænomenon which is rare at land, though frequent at sea. The seamen call it looming. Philosophy is as yet in the rear of the seamen, for so far from having accounted for it, she has not given it a name. Its principal effect is to make distant objects appear larger, in opposition to the general law of vision, by which they are diminished. I knew an instance, at York town, from whence the water prospect eastwardly is without termination, wherein a canoe with three men, at a great distance, was taken for a ship with its three masts. I am little acquainted with the phænomenon as it shews [ 136 ][ 137 ]