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every where present themselves to the enchanted eye, the face of creation would be parched, withered, and consumed.
That incomprehensible wisdom which guides and balances creation, of which we are destined to know nothing but from its effects, leaves no part of its works imperfect or unfinished. The same creative power has therefore ordained, that the superabundance of that element which, without some different disposition, would lead to the annihilation of all life, and of every vegetative germ, shall be made the great means of preserving both. And the more we enter into an examination of those laws and operations of nature wliich appear so wonderful, and which in many parts are so inscrutable, the more are we astonished and charmed in contemplating their well adjusted harmony and surprising beauty.
That the immense portion of heat which pervades the earth in the warm season is, from its inherent properties, constantly aggregating in numberless masses of various dimensions, there does not remain in my mind the smallest doubt. And what else is the electricity that is produced by art, and made to issue from a machine, but a simple colsection or multiplication of that sustaining or animating principle, drawn suddenly io a point by some strong attractive property?
To this inberent principle alone, I conceive, may be traced the origin and existence of those bodies of unusual heat, of which Mr. Jefferson, in his celebrated Notes on Virginia,* makes mention, and which are so frequently felt by curious observers in the summer months. That enlightened philosopher did not attempt to explain either the cause of their formation, or what he supposed to be their ultimate end and use. I propose, but with all becoming deference, to offer my opinions in relation to both. And since nothing is known to exist that does not bear the impress of unequivocal design, and with a manifest tendency to usefulness, it cannot be deemed an irrational speculation to trace to some important end, the origin, design, and purpose of their formation.
I have witnessed these warm moving bodies in almost numberless instances. They were familiar to me in my early life, my residence then being near the foot of a ridge of very considerable elevation in the eastern part of Dutchess county; and the supposition follows that they are familiar to many others. At the same time, I am led to believe, that those who reside in elevated situations, have few op
* "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 beat of the human body. Some of them perhaps go a liule beyond it. They are of about twenty or thirty feet diameter horizontally. Of their height we have no experience, but probably they are globular volumes, wafted or rolled along by the wind. But whence taken, where formed, or how generated ? They are not to be ascribed to volcanoes, because we have none. They do not happen in the winter, when the farmers kindle large fires in clearing up their grounds. They are not confined to the spring season, when we have fires which traverse whole counties, consuming the leaves which have fallen from the trees. And they are too frequent and general to be ascribed in accidental fires. I am persuaded their cause must be sought for in the atmosphere itself; to aid us in which, I know but of these constant circumstances; a dry air, a temperature as warm at least as that of the spring or autumn; and a moderate wind. They are most frequent about sunset; rare in the middle part of the day; and I do not recollect ever having met with them in the morning.'
Notes on Virginia.
portunities of meeting with them; while those who are much employed in smooth grounds in a valley, will often remark them. For this, I think a very satisfactory reason may be given. Their specific gravity must necessarily carry them to the lower grounds, even supposing some of them to have been formed in higher parts; though I think it very doubtful if any are produced in such places. I suppose the fact to be, that aggregation takes place more easily and more rapidly in an open country, or at the foot of high hills, where the land is level and well cleared, owing to the increased quantity of heat that is presumed to be deposited there, and the greater equality of the ground. Experience sufficiently shows, that an intense degree of heat will prevail in a valley, or over a plain, when the tops of high ridges are found to be comparatively cool.
Of the truth of the fact that these mysterious bodies are mostly formed in low grounds, I feel thoroughly persuaded; for as often as I have ascended the side of the ridge just mentioned, which was in almost numberless instances after the sun had disappeared, I have no recollection that I ever came in contact with one of them. They are most commonly felt in a warm evening after a sultry day, about sunset, as Mr. Jefferson states, or soon after, and invariably when the wind is from the south or south-west. The power of the sun being then withdrawn, and the air being somewhat cooled, these warm moving bodies make a more sensible impression upon the observer when he meets with them. I have sometimes encountered several in the course of an afternoon and early in the evening; but more frequently in a meadow than in any other place. They appear to me to be infallible precursors of a thunder-storm, which usually happens on the succeeding afternoon or evening.
From the frequency of these bodies, during the most oppressive part of the summer, (and I believe they are seldom met with in any other season,) I am led to believe, that if a line of men were placed across a piece of low and level ground, for the extent of a quarter or half a mile, supposing it to have a north and south direction, with instructions to notice the state of the atmosphere, imagining a gentle current of air from the south, they would find them very numerous. It is not to be supposed they are all of equal magnitude; I presume they are of various sizes ; though it has always appeared to me, that those which seemed largest, seemed also to contain the highest portion of heat. Not only do I feel well persuaded of this fact, but I think the conclusion warranted from the nature and properties of the bodies themselves. I deem it proper to remark in this place, as it
mind to corroborate the hypothesis I have assumed, and at the same time is in itself a circumstance not a little remarkable, that I have never in the course of my life met with one of these warm bodies either immediately succeeding a thunder-storm, or yet for some time afterward. The plain reason I suppose to be this : they have been removed by the combined operation of the elements ; and in their removal, a law is fulfilled that is not only indispensable in the economy of nature, but in the highest degree beneficial in many of her movements. The atmosphere is then no longer charged with a burdensome portion of heat; but from the fierce concussions that have
goes far in
taken place, it is rendered serene, delightful, and healthful. This brings me more immediately to the point which I have in view, and which it is my present purpose to explain, namely, the common phenomenon of electricity issuing in profuse and splendid streams from the clouds.
That electricity should exist in a considerable degree, even if it exist at all, in mere vapor, or in the higher or colder regions of the atmosphere, I believe to be a most manifest absurdity. Since showers of hail are common, we want no farther evidence of the intense cold which prevails in the higher regions; and it is utterly repugnant to common sense, to imagine that electricity can be engendered or preserved among masses of congealed and congealing water.
Whenever the atmosphere becomes loaded with a heavy portion of vapor, the formation of clouds is the natural consequence; and being constantly kept in motion by currents of air, they soon magnify to an unknown extent of surface and depth. As the higher parts must necessarily communicate with those regions which are attended with extreme cold, and as their weight must ofien press them very near to the earth, it follows as a thing of course that their influence becomes both extensive and powerful.
The efforts of nature to keep up a general equilibrium in all her movements, are pretty well understood. These efforts in equalizing heat and cold, are familiar to most people. The cool air constantly rushing through crevices into a tight room made warm, sufficiently illustrates this point; a reference, however, to the operation of an air-furnace, shows it more conclusively. Whenever, therefore, a very extended body of dense vapor is put in motion, and sweeps over the earth, being borne along, as is frequently the case, by strong currents of cold air, I think it fair to presume, that it must attract to itself an immense portion of the heat that is spread over its surface. To my mind, nothing is more evident than this simple process; for I think the conclusion follows irresistibly, that those numerous bodies of heat which are floating on the surface of the ground, are drawn forcibly into the mass of cold vapor; and the instant they come in contact with the colder and denser parts, being first much compressed, they explode, producing the usual phenomena of vivid lightning and loud peals of thunder. The difference in the force and duration of explosions, I ascribe to the difference in the magnitude of these bodies of heat. Beside, in their ascent into the clouds, it seems quite probable that in many instances a junction of several may take place. In such cases, it is reasonable to suppose the concussion becomes proportionally tremendous. But I do not restrict my view in relation to this point solely to those moving bodies; for the belief forces itself very strongly upon my mind, that the influence of an immeasurably large body of cold vapor, moving with resistless force through the atmosphere, attracts to itself, in masses or currents, all the redundant portion of heat that remains upon the surface of the ground. These masses, or currents, or by whatever name they may be called, are operated upon so forcibly, that they must very soon become completely aggregated bodies; that, in their ascent into the clouds, they are subject to the same operative effects, and produce the same consequences, that are ascribed to the bodies of
heat which have already undergone review. Indeed, the supposition appears to my mind not unreasonable, that these latter bodies occasion even a fiercer concussion among the elements than the others, for the reason that they are perhaps larger, and therefore contain within themselves a higher degree of heat.
This I take to be the natural and true source of those wonderful displays of the electric property, that emanate in such surprising quantities from heavily condensed vapor, driven by strong winds, which, beyond all doubt, originate in high and cold regions.
From the united effect of these operations, the influence of which must be inconceivably great, springs that extraordinary change in the disposition and character of the atmosphere which commonly succeeds, and which is at once so grateful and even so necessary to the existence, health, and comfort of the whole animal and vegetable creation. The air, as before remarked, is made elastic, pure, and salubrious, imparting fresh spirits and vigor to every living thing, whether animate or inanimate. The earth is relieved from the great mass of heat that was spread over it, and which, were it of long continuance, would become altogether insupportable. The air by means of it would be rendered unfit for respiration, and life could not be sustained.
In a few instances I have met with these bodies of warm air in the forenoon; but this is not common. I recollect an instance several years since, in which I had occasion to pass Hudson's river, opposite the city, early in the day. When we were near the Jersey shore, in an open boat, it being about eight o'clock in the morning, with a gentle breeze from the south-west, the day very sultry, we passed through two of these bodies of warm air, which were quite near each other. They seemed to be uncommonly large, and were of such an extraordinary degree of warmth, as to attract the notice of all the passengers. I think they were marked with a higher portion of heat than any I ever recollect to have noticed. About the hour of five or six in the afternoon, a fierce tempest came over the city, and the clouds discharged a large quantity of hail, attended with a more than ordinary emission of the electric property. Many of the hail-stones were as large as ounce balls.
It becomes unnecessary to remark, because the fact is familiar to us all, that after the commencement of cool weather, we have seldom
any thunder. The reason of this appears sufficiently obvious. The great portion of oppressive heat is withdrawn from this division of the earth, and its place is supplied with air from the colder regions.
This phenomenon, I presume, is occasioned solely by the agency of the sun operating on vapor. Vapor evidently assumes a very variable character. That which is visible to the eye, and even tangible, goes under the usual denomination of fog. As soon as the power of the sun is brought to act upon it, it immediately becomes rarified, and we see it begin to asceud. After rising to a certain degree of elevation, it forms itself into clouds; but it often hangs
for a time on the declivity of ridges, before it attains that region in the atmosphere which seems to inark the usual distance of the clouds from the earth. While moving in the atmosphere, they reflect the various shades of light, according to their degree of density and their position in relation to the sun.
There is another kind of vapor of a character so extremely subtile, as to be invisible to the eye; though, had we sufficient acuteness of vision to perceive only a small part of the operation, our wonder, I think, would be greatly excited. This comes under the general denomination of exhalation or evaporation. It comprises all that immense mass, which, by the resistless energy of heat, is absorbed from the boundless surfaces of water, from the earth itself, and from every species of vegetation. At certain periods, the effect of this is so great, that objects at a moderate distance are made to appear indistinct; although, when superficially examined, the atmosphere presents the appearance of much purity and serenity.
From the known properties of light and heat, we can readily perceive, that when they are brought to act on vapor, the effect becomes very striking. Under some circumstances, it is made to reflect various hues; under others, it becomes an extraordinary magnifying power. At times, if we cast our eyes across a body of water, in order to examine a distant shore, we are deceived by an illusion which in some situations is not uucommon, and which seems to be intimately connected with the present inquiry. The water near the shore has the appearance of being elevated, and presents a real obstacle to a correct view of the land. There are three situations at which this phenomenon is sometimes visible when standing on the Battery. One is at the point of Staten Island at the Narrows; another is at the Kills, so called, between the Jersey shore and the north point of the island; and the third is near Weehawk, at the distance of about three miles. There are also other situations on the East and North river, where it is equally visible. The cause can be no other than the influence of light and heat on the current of evaporation, which becomes reflective, while it serves as a magnifier. It must be borne in mind, that these effects are visible only where high grounds stand in the rear, or are contiguous. The light from these grounds probably has a réacting tendency, assisting to produce the effect in question; giving to the water the appearance of being raised above its ordinary level, accompanied with a peculiarly luminous aspect. It is my opinion, that when this happens, evaporation may then be supposed to go on with greatest force; for it strikes my mind that this law is by no means uniform in its action. At times its influence would appear to be very great; at other times partial; and under some circumstances wholly suspended. All this I conceive to be owing to the state or condition of the atmosphere itself.
But I am strongly inclined to believe, that the manner in which evaporation goes on, differs materially in one respect from what may perhaps be the general opinion. It appears to me that the vapor is drawn together in columns or bodies, and ascends in that
that it must necessarily be subject to this mode of operation ; and that these columns or bodies in their character and movements are very