« AnteriorContinuar »
gave a refreshing coolness to the crescent-like area which they overshadowed. The sun was yet low in the east, so that, though his empire was thus rapidly invaded, he could still shoot his beams far up the slope, beneath the fog, which had now advanced it front, so as to appear, from our stand-point, one broad mass of darkening clouds. The morning dews had not yet been dissipated, and the sun's rays, illuminating the vast amphitheatre not shaded by the clouds, caused every dew-drop on leaf and flower to glitter like diamonds. The circles of light and shade, standing in strong contrast before us, with their beautiful florai ornaments, produced a scene that was gorgeous in the extreme.
But the clouds, accumulating faster and faster, soon covered not only the mountain-sides, but overspread the whole area of the Cove; and, advancing eastward, covered the face of the sun as with a curtain, shutting out his rays from the landscape around. We were now startled by a sudden flash of lightning, succeeded, instantly, by the roll of the thunder, which, reverberating among the mountains, prolonged its tones to a duration unknown to the dwellers among the low-lanils. The rain, which for a few minutes had fallen in a feeble drizzle, now descended at once in a copious shower, as though it had been awaiting the signal of the electrical flash to do its errand of mercy.
A word here, about the form of these mountains, before proceeding with farther descriptions. Like all mountains composed of stratified rocks, those of North-Carolina run in lengthened ranges, mainly, from north-east to southwest. In countries where the unstratilied rocks prevail, the mountains are often thrown up into dome-shaped forms. Here and there, however, in North-Carolina, there are points which rise dome-like, a thousand feet above the ordinary elevation of the surrounding portions of the mountains; but they differ in nothing, except altitude, from the geology of the country at large. These domes, in the section of country under consideration, attain a height of three thousand feet above the beds of the rivers, and about five thousand four hundred feet above the sea-level. Some of them reach an elevation of two hundred or three hundred feet above the line at which the ordinary forest-trees can grow, and are destitute of timber, though covered with grasses and flowers. Here and there a group of briars, laurels, azaleas, and other shrubs add their presence to vary the scenery of these celestial prairies.
These elevated domes have much to do with the formation of clouds and the production of rain. They are locally called balls, from their round appearance and naked surface. In the clearest days, often, the clouds can be seen forming around them at a greater or less distance above or below their summits. At times the rainfall is limited to the area around the ball, where the cloud spends itself, so that its remaining vapour is drifted off or dissolved again in the atmosphere. At other times the clouds
accumulate largely, and either from the influence of currents of wind, or from electrical action, they move off so as to water the surrounding mountains and intervening valleys. It it not unusual for two balls, or for the summits of the lower mountains, to be forming wreaths of clouds around their brows at the same moment. These clouds, not unfrequently, are attracted towards each other, and thus the vegetation cf the intervening districts has an additional chance of receiving new life and vigour from the rains yielded by this means.
• It is these occasional showers which servi to keep up the mountain-springs and streams in perpetual flow, and which eupply to the animil kingdom the water it demands, in a purity almost equal to the dews of heaven. The general rains of this region, as distinguished from those of local origin, come, usually, from the west and south-west, in broad sheets of cloud overspreading the whole sky.
On the seventeenth July, 1857, I set out from the head of Valley River, a branch of the Hiwassee River, to measure the height of the ball upon Valley River Mountain. Making the measurement with "Locke's level," I could at least, gain a close approximation to the true height. The distance from the river's bed to the top of the ball was about five miles, and the elevation two thousand nine hundred and eighty-seven feet; or about three thousand feet above the bed of the Hiwassee at Murphy. North Carolina.
Before reaching the top of the main ball, i cloud came sweeping along from the direction of the Tusquitta Mountain, to the south-vest, and poured down its rain as it progressed. It reached us, in our elevated position, iu the form of a dense fog, as all clouds appear when we an in their midst. It first struck our mountain at a point about five hundred feet below its suamit, and then rolled along amidst the trees to the top of the ball. While hovering there, ai a hen over her brood, it sent an arm down the eastern side of the mountain, above the treetops, to a distance of several hundred feet; and then, as if reluctant to lose any portion of its mass, this arm was drawn up again into the bosom of the cloud. Rendered light and air)', from the loss of its rain, the cloud soon a»ept off to the eastward, so that our measurementi could be completed.
Nearly all the balls in sight, more than « half-dozen in number, and many of the higher portions of the lower ranges of these mountains, were repeatedly covered by rain-clouds dunnf the day, which were either formed upon them, or floated to them from one or another of t« surrounding elevated points. Four or fire« these clouds passed up Valley River towards ft but were generally exhausted of their rain before reaching our positions. The valley is Wrow, being little more than a mile in width, w runs in a south-west direction to the Hiwassee River.
These showers presented varied appearanceas they succeeded each other. Tbe first w» from a cloud, the margins of which were equal in depth and density to the main parts of its body: its breadth was nearly equal to the width of the valley. There being little wind, the rain fell vertically, and presented the appearance of a large curtain of semi-transparent gauze, suspended from the cloud to the earth, having a length of two thousand feet. A second shower fell, an hour afterward, from a cloud with attenuated margins, but dense centre. The sheet of water which fell from it presented the appearance of a semi-transparent fog in the centre; but gradually shaded off toward the margins, into a misty haze, scarcely obscuring the objects in the back-ground. A third, which occurred during our descent, was from a dense black cloud that overshadowed the valley and half the adjacent mountains. It had also great length to the westward. The body of water which it afforded was so dense, and the distance through which the eye had to penetrate so great, that every object in the back-ground was as completely obscured as though the pall of midnight had been drawn across the valley.
We had reached a position two thousand feet below the summit, and one thousand above the base of the mountain, when this shower had so far passed over as to allow the sun to shine out brilliantly from the clear sky in the west. Immediately a rainbow of the greatest beauty was produced. The top of its arch reached a little above the top of the ball, which we had just measured, thus throwing the main part of the bow below its level, and giving it a back-ground of the richest green which the foliage of the mountain could afford. Two mountains of unequal height intervened between us and the ball. The nearest one was much the lowest, while the other rose half-way to the summit of the ball. Upon the entire slope the lines of the rainbow were presented in a richness of colour far excelling anything of the kind I had ever witnessed before; the accompanying secondary bow being about as brilliant as the ordinary rainbows of the lowlands.
Clayton, Georgia, is located not far from Rabun Gap—a low depression of the Blue Ridge. This depression consists of some swampy lands in which the head-waters of the Little Tennesseee and the Savannah Rivers take their rise. The mountains on each side of this gap rise to the height of fifteen hundred feet. On the morning after my arrival at this town, my travelling companion awoke me, to call my attention to a wonder.
The sun was just rising. On looking out at the window, toward the north, I beheld a vast volume of fog, filling Rabun Gap from base to summit, and occasionally extending even above the highest mountains. It was as white as snow, and resembled a vast deluge of cotton as it falls loosely from the gin. In front of the main gap, and between it and the town, there stands a small mountain, detached from the principal range, with a gap upon each side. The fog, as it rolled through the main gap, was de
flected into the smaller gap to the east of the little mountain.
On viewing it for a few minutes, I was soon startled by noticing that, though the whole immense volume of the fog was rolling forward at quite an observable rate of speed, yet it never passed much beyond the southeru side of the little mountain. Onward it came, with a sufficient force and bulk to overwhelm, in its darkness, the whole southern side of the Blue Ridge. But beyond the line named it could never pass. A barrier existed there in the different conditions of the atmosphere, which at once dissolved the fog, and left the air beyond as transparent as ever. Once in a while a small portion of the fog would whirl forward, a few hundred feet beyond the main mass, like a bold leader in front of an army, as if to encourage the forces behind to move onward with greater daring. But all was in vain, as leader and follower were quickly involved in a similar fate. The law which controled the movements of the fog, said to it emphatically: "Hitherto shalt thou come, but no further."
Turning to my friend, who had patiently watched me while I was absorbed in contemplating this wonderful phenomenon, I asked him if it had ever occurred before. "Yes, sir," he answered, "it occurs every clear morning, from spring to fall. Beginning to roll through a little before the sun appears above the horizon, it continues till eight o'clock sometimes, and as late as ten at others; and thfs it repeats every clear morning, and has repeated, doubtless, ever since the dry land appeared, and the mountains and the rivers were formed."
Again I turned to view the fog, and found it coming on to its fate, as regardless of consequences, apparently, as we poor thoughtless mortals are when treading upon the very verge of destruction.
As explanatory of the phenomena at Clayton, and of the production of clouds and rains in the mountains, a few general principles in natural philosophy must be stated:
At all temperatures, moisture exists in the atmosphere in an invisible state. It sustains itself there in the intervals that exist between the particles of air. These intervals are either partially or wholly filled with vapour constantly arising from the earth. When they are wholly Billed with vapour, the atmosphere is said to be saturated. An increase of temperature, by dilating the air, increases its capacity for moisture; while a diminution of temperature is followed by contrary effects. But the capacity increases at a faster rate than the temperature, so that while the air, at thirtytwo degrees Fahrenheit, can contain only the one b undred and sixtieth part of its own weight of vapour, at one hundred and thirteen degrees it can contain the twentieth part of its weight. Thus it appears that while the temperature advances in an arithmetical series, the capacity is accelerated in a geometrical progession. A considerate increase of temperature, therefore, will enable even a saturated atmosphere to receive a greatly augmented amount of vapour, and, as it were, to swallow the clouds that may pass into it, without any diminution of its own transparency. On the contrary, when the temperature is diminished by the rapid union of two currents of air, saturated with vapour, the one being warm and the other cool, the average temperature is so reduced that an excess of vapour exists, which is incapable of sustaining itself in the diminished capacity of the air, and is necessarily precipitated in the form of rain. But when two currents of air, not fully saturated with vapour, are brought into contact, the precipitation of moisture is slight, and mists, only, are produced. When the mists, thus precipitated, are near the earth, they are called/oys, but when high in the air they take the name of clouds.
Saussure and Kratzenstein have investigated the nature of fogs and mists. The vapour, in this condition, is found to consist of minute globules, upon which rings of prismatic colours were discovered, like those seen upon soap-bubbles, but which are never observed upon drops of water. From this discovery it was concluded, that the globules are hollow, and filled with air or gas. The size of these globules is greatest when the atmosphere is very humid, and least when it is dry.
Another fact must be noted. The temperature of the air diminishes with the altitude, but the law of decrease is very irregular, being affected by latitude, seasons, hours of the day, and a diversity of local circumstances. It may, however, be assumed as a general rule, that a loss of heat occurs to the extent of one degree Fahrenheit, for every three hundred and fortythree feet of elevation. But this is an average result, for the rate of decrease is very rapid near the earth, after which it proceeds more slowly, and at the loftiest heights is again accelerated.
From this brief statement of the general principles governing the production of fogs and clouds, it will be apparent that the higher portions of the mountains of North-Carolina must be refreshed by frequent rains. The elevated balls, ever clad in mantles of cool air, stand, as so many custom-house officers, to exact tribute from all the currents of air laden with vapour, from the warmer regions below, which attempt to sail over their summits. These currents of air cannot but pause, when richly freighted, to divide their treasures with the thirsty soils and mountain-springs. And even when they are lightly burdened with vapour, and no rain can be condensed from them, these passing currents often yield copious clouds of fog, covering the vegetation, by contact, with moisture, and promoting its more vigorous growth.
Nor are the mountain summits alone, in the exactions they make upon the moving atmosphere for its vapours. The mountain bases, all along the rivers and larger creeks, cool the surrounding atmosphere during the night, while the waters of the streams, retaining their warmth, send upward a plentiful evaporation. The vapour which is thus formed, rising into contact with the over-hanging colder air, is condensed
into fog, and floats above the streams till the morning sun sets it in motion, or dissipates it by increasing the temperature of the air along the mountain sides.
The phenomena of the fog at Clayton can now be easily explained. The Little Tennessee River takes its rise in Rabun Gap, and runs northwest. By the junction of several large creeks, heading in the Blue Ridge, the river, soon after emerging from that mountain, becomes quite a considerable stream. It is walled in on each side by other mountains, of fifteen hundred to twentyfive hundred feet in height, which extend northward, as cross-ties, from the Blue Ridge to the Great Smoky Mountain. These mountains are covered with forest-trees from the base to the summit. The sun, during the hottest hours ol the day, teems down its rays into the valley, and imparts a great amount of heat to the waters of the river, as well as to the rocks among which it runs. The temperature of the water is thus kept up during the night, while, at the 6&me time, the surrounding mountains cool the overhanging air. The vapour, which rises rapidly from the heated water, coming into contact with the cold atmosphere above, is converted into fog. As the sun rises in the morning, bis rayi at once act upon the air south of the Blue Ridge, where no obstruction exists; but his heat cannot affect that of the narrow valley of the Tennessee, till the sun attains a sufficient elenuon to overcome the altitude of the mountain upon its eastern side. The rarefaction of the atmosphere on the south side of the Blue Ridge, while that of the Tennessee valley remains at a lower temperature, produces a current of air front north to south that bears the fog along with n through Rabun Gap. But here the increased heat, expanding the air, or gas, in the globus of vapour composing the fog, bursts the bobble. and the fog is dissolved by absorption into the warmer atmosphere, as transparent vapour.
The fog which rolled through the notch into Tuskegee Cove, had, no doubt, formed the BjP previous, in tho valley of Cheoah River, 1^ to the west and running northward. Overshadowed by high mountains, the atfflojpbeK of that river must have been cooler than thai; « the Cove, into which the sun was bngmjf shining. Two masses of air, both of wco must have been saturated-with vapour, btw thus brought into contact, the temperature w diminished and the excess of moisture prw?" tated.
Tellulah Creek, taking its rise southward, «£ Nantahala River, is the main branch of t» Cheoah River. Big Snow-Bird, Little Sno*Bird, and other considerable stream8',arejr" tributaries. The Indian names are of Cbero*« origin. . vj
In this connection another meteorologi* phenomenon, occurring in the mountains ^ North-Carolina and Tennessee, may be noncw It is not one of the peaceful nature of the fog rain, but, though limited in its range, mustterrific beyond conception. An eye-»TM ■ describing one of these scenes to tbe writer, co* veyed a moat vivid impression of the fearful: character of the elemental strife accompanying the descent of waterspouts upon the land, if water-spouts they may be called.
Once in a generation or two, perhaps, a waterspout bursts upon some elevated point of a mountain. Previously to its descent, the clouds are seen moving to and fro, and commingling in a confused manner, somewhat as the circling eddies of a vast whirlpool; When concentrated above or around the mountain's summit, the cloud acquires such a density as to wear the appearance of the blackness of darkness. The roll of the accompanying thunder is deafening, and almost continuous, shaking the eternal hills to their base; while the flashes of lightning, following each other in quick succession, afford a glare of glimmering light nearly as luminous as that of the sun. Then comes a river of waters, dashing down the mountain side, and tearing up, in its resistless progress, earth, rocks, and trees, so as to create, in its course, a deep canal. The amount of water at times discharged from such clouds is immense, swelling inconsiderable streams into great rivers.
Many years since, a water-spout burst upon the North Mountain, to the westward of Newville, Pennsylvania, carrying destruction in its course. Many cattle and hogs were drowned at the foot of the mountain, where they were confined within inclosures, preventing escape. The largest rocks were torn from their beds, and a deep chasm excavated from the top of the mountain to the valley. Its course can now be traced by the difference in the trees within the channel from those on either side—a growth of pines now occupying it, instead of the oaks and hickories of the surrounding forest.
Another water-spout fell upon the western end of the Chilhowee Mountain, where it passes the Little Tennessee River, about the date of the first settlement of the country. Its course is marked, like the one at Newville, by a large growth of evergreen trees. Again, on the west side of the same mountain, not far from Tuckalechee Cove, and near Little River, a waterspout fell, not many years since, carrying away a distillery, around which, the day previous, being the Sabbath, the young men of the vicinity bad met, in a frolic, and perpetrated some enormous blasphemies—in their drunken revels, undertaking to make a mock of religion, by the administration of its sacraments. Monday was ushered in by as clear a sun as ever shone. In the course of the day, however, the thunder pealed forth a signal, startling the neighbourhood into fixed attention: there they beheld, gathering upon the mountain's brow, the ominous cloud, that soon burst out into one vast deluge of water, which, descending down the mountain's side, laid desolate the very spot where the profanation of Heaven's ordinances had occurred. The terror created by this celestial phenomenon was such as to produce a religious revival, accompanied by the conversion of many of the thoughtless fellows who had
taken part in the iniquities of the preceding sabbath.
Having seen the traces of all the waterspouts noticed, and having heard the descriptions of eye-witnesses, to the accumulation of the cloud which produced the rain-fall, in one case Bo furious in its descent, I concluded, as usual, that there had been a concentration to one point, of nearly all the water yielded by the cloud, through the agency, probably, of a whirlwind motion of the air controlling it; but this theory had to be abandoned, as soon as I completed, for myself, the investigation of the facts connected with the great fall of waterspouts, upon Tusquitta Mountain, on July 8, 1847.
An intelligent professional gentleman, who visited the scene soon after its occurrence, described the chasm, excavated in the earth, as having a depth of several feet, with its sides cut out as vertical as if dug with the spade. The roots of the trees and plants, beneath the surface, were cut off as squarely as if done with the knife, At the surface, close up to the sides of the chasm, nothing seemed to be disturbed. The shrubs and grass, and even the fallen leaves upon the ground remained unmoved, as though no running water bad come into contact with them. This was the condition of things where the waterspout first struck the earth; and as tha excavation, at the point of origin, had a width of but a few yards, the whole volume of the descending water, he concluded must have [been concentrated within that space, and continued thus contracted till the contents of the cloud were exhausted. In descending the mountain, along the line of the widening chasm, evidences existed that the torrent, in places, had attained a depth of fifty or sixty feet, uprooting in its course the largest trees, and removing immense rocks from the avenue created in its descent to the valley below.
In all the descriptions given, I had inferred that but a single water-spout had fallen, at the same time, from any ons cloud. Such had been the case in the old ones, grown up with evergreens. But very different, indeed, had been the results on Tusquitta Mountain.
In the month of May, 1859, I called upon Robert Martin, Esq., who resides in the Tusquitta valley, near the spurs of the Tusquitta Mountain. He had resided there in 1847, when the water-spouts fell npon that mountain, July 8th. From his statement, and that of Mr. Pierce, his neighbour, who also noticed the whole of the movements of the clouds, during j the space of three hours, or from first to last, I make up my statement:
The clouds were some two hours in forming. I One group gathered in the south-east, another in the south-west, and a third in the south. j The unusual commotion among them, as they j were forming, attracted the attention of these gentlemen, and riveted them to the spot, where each one stood, near their own doors, a halfmile apart.
When pretty fully formed, the clouds commenced moving rapidly, in eddies of many whorls, toward Tusquitla Ball. Salutations of thunder, from the first, passed' between them, as though cloud called to cloud, in organizing for the coming conflict. The play of the lightning, at first occasional, became almost continuous, as the constantly accumulating masses began to move swiftly toward a common centre; while the thunder, increasing also in frequency, goon became terrific. In addition to the thunder, and just before the rain began to fall, there came a succession of sharp, keen, cracking sounds, lasting for ten or fifteen minutes, which resembled the sharp crack of the electrical spark; and then came a crash, as if ten thousand pieces of artillery had been discharged. The earth fairly trembled with the concussion. There was also a loud roaring sound, independent of all the other sounds, for some minutes before the clouds came into contact; and when they did meet, they shot instantly upward, with great velocity, like an arrow shot from a bow. The forests, a few rods distant, became so dark that nothing could be seen.
The rain now began to fall in torrents. In a few minutes the small spring branch, at Mr. Martin's, having its rise a mile or so further up the mountain, was swollen into a river. In an hour the rain was over, and the sun again appeared as bright as ever.
The gentlemen named then commenced an examination of results. About three hundred feet above the head of the spring-branch, a water-spout had fallen, excavating a canal ten feet deep, and seventy-five feet wide at its head. The side-walls, at this point, were perpendicular, while, farther down, it varied, both as to depth and width; the vast body of water, of course, obeying the general laws controlling the descent of that fluid down a steep inclination. This torrent, in rushing down toward the springbranch, at an angle with the line of that stream, could not make a sudden turn, but dashed across, rising on the opposite side to the top of a spur of the bill, thirty feet high, when, from the farther side, it naturally fell into the channel of the branch, swelling it into the proportions of a river.
Upon more extensive examination, the waterspouts (if these rain-falls may be so called) were found to have been very numerous; nearly a hundred canals existing within an irregular area, not exceeding three miles in length. The largest one was eighty feet in width, and others not moro than eight or ten feet.
But these excavations were not the only effects produced during this hour of awful sublimity. Many forest trees bad been struck by the lightning, and explosions of electricity, from the earth, had thrown out large masses of clay and rock, in many places, producing excavations of sufficient depth end width, often, to bury a common hogshead; the vegetation, all around these spots, being scorched and withered by the electric fluid.
The seat of these water-spouts lay about four miles from the Tusquitla Ball. Two gentlemen
were upon the top of the ball when the cloud reached that point. One of them, Mr. William R. Martin, described the rain-fall as so dense as to almost suffocate him. The sensation wis such as is experienced when under water; and the only remedy was to lean the body over, so as to have a little space of air to breathe from, beneath the breast.
The volume of water discharged from these combined clouds was such as to raise the Hiwassee River very much higher than it had ever been known before, or has been since. Here, too, the contest between cold water an J alcohol was repeated, a little mill and distillery having been swept away, and the mill-stones for ever lost in the depths of the Hiwassee.
On the twenty-third of May, 1859, I commenced a personal examination of the area upon which the so-called water-spouts had fallen. I was accompanied by Dr. G. G. McCoy, of Fort Hembre.
In ascending the mountain, we could see, at one time, more than a dozen of the excavations. The first one measured, was aboui twenty-five feet wide at its head, and must hare been some six or eight feet deep. It was mil;.' about twenty yards from the top of the moontain-spur, upon which the water had fallen. The torrent had passed down into a trough-like depression in the mountain-side, cutting oat id channel as it progressed; but there was only a very slight dishing, where the spout first fell, insufficient, wholly, to accumulate sufficient water to make such a canal, within the space of twenty yards. Then, as there had been no washing away of the surface rubbish, above the point of excavation, it would appear that the agency, which produced the cutting, must have begun its work at that spot.
The next excavation examined, was where two spouts had fallen, close to each other, being separated, at the head, by about three rods of unbroken ground. Each of these canals measured forty feet in width, and when united, a few rods below, the channel was sixty feet in width. These two are not in a trough, or concave portion of the mountain, but fall into one some distance below their junction. The head' of both are about twenty yards from the top of the mountain-spur.
The same general features were present in the other excavations, and additional descriptions are, therefore, not necessary.
One remark only need be ventured, in relation to the agency which cut out these channel*. That it was water, none can doubt. But that the water was concentrated to one point, by a whirlwind-like action of the cloud, compressing it* falling rain-drops into one compact sheet, capable of cutting away all the mere clays «nd fragmentary rocks upon which it might fall, s disproved by the multiplicity of excavations upon Tusquitta Mountain. The only remaining solution of the mystery, then, in relation to the manner in which the rain becomes condensed, in what are called "land-spouts," is tobefoond in the statement of philosophical principles upon