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“”Tis pleasant, by the cheerful hearth, to hear Of tempests, and the dangers of the deep, And pause at times, and feel that we are safe : Then listen to the perilous tale again, And with an eager and suspended soul, Woo terror to delight us.” Southey. WE now enter upon that part of our subject which treats of the atmosphere, the waters of the globe, and the mountain rocks of which it is composed. No department of natural history abounds more in important facts and interesting conclusions. We commence first with “METEoRology.” The science of meteorology describes and explains the various phenomena which occur in the region of our atmosphere. The word is of Greek origin and means aloft or elevated. It is a study which has deeply engaged the attention of men in every stage of society, from the roving savage to the refined votary of wealth and pleasure. The moment we cross our thresholds we commit ourselves to the influence of the weather; but the hardier class of the community, the shepherd, the plowman, and the mariner, whose labor creates or procures the staple articles of life, are always exposed by their occupation to the mercy of the elements. They are hence led by the strongest motives, to examine closely the varying appearance of the sky, and to distinguish eertain minute alterations which usually precede the more important changes. Thus Virgil in one of the most, beautiful passages of the Georgics gives for the use of the mariner and husbandman, the warnings which in his time were thought to precede approaching storms of wind, which he observes, well contemplating, the careful husbandman will gather his herds into their stalls; they are eleven in number. I. The agitation of the sea, the swelling waves rolling upon the shore. II. Noise from the mountains of the rustling leaves and crackling branches. III. The roaring of the surf as it breaks upon the shore. IV. The murmuring of the groves. V. The flight of sea-birds and their screams. - VI. Their playing or sporting on the shore. VII. The herons forsaking their accustomed marshes and mounting aloft. VIII. The fall of meteors, portending winds, and which is thus similarly alluded to by Milton : “Swift as a shooting star, In Autumn thwarts the night, when vapors fired Impress the air; and show the mariner From what point of his compass to beware Impetuous winds.” IX. Nocturnal streams of light, probably the Aurora. X. Straws rising and floating in the air. XI. The play of floating feathers driven about upon the surface of the pool. Next he gives twelve prognostics of rain, which were thought so conclusive in their indications that he observes “Never hath a shower hurt any person unforewarned,” viz: thunder from the north; the clash of east and west winds, and the flight of the cranes into the vallies to avoid the impending tempests, Heisers snuffing the wind; the circling flight of swallows round the water, and skimming over its surface. The croaking of the frogs; ants busy with their eggs. The rainbow, which was then supposed to have drank the water that supplied the clouds. The hoarse murmur of the flocks of crows. The diving of sea birds and of swans; smoothing and oiling their plumage. A solitary bird pacing the sand; and lastly the gathering of fungous excrescence on the wick of the lamp, causing the oil to sputter and the flame to emit sparks. Prognostics of the coming weather drawn from the appearance of the
INDICATIONS OF THE WEATHER. 117
moon or sun, are also given. I. From the moon; darkened when new, she betokens rain. If red, wind; if serene in the fourth night she promises fair weather for that month. II. From the sun; if in rising, spotted, or showing only the centre of his orb, rain is portended. If of a bluish color in setting, rain, if red, wind. If spotted at setting, rain and wind; and if bright at rising and setting, clear weather with a northerly wind.
After these beautiful descriptions, which bring the poem home to every one, follow nine indications of fair weather. The brightnes of the stars, and of the rising moon. The unclouded sky, and kingfishers not expanding their wings to the sun; sows no longer tossing wisps of straws into the air. The clouds floating low; the silence of the owl at sunset, whose hooting was once supposed to forebode rain. The falcon soaring after the lark, and the crows social, and cawing with clear notes. Many of these signs are even now considered as harbingers of the coming change of weather, and more particularly the formation and arrangement of certain clouds, to which we shall again allude. No doubt the early observers of the weather often mistook the indications of those aspects we have mentioned, and inferred conclusions from mere casual circumstances.
The signs which usually precede the coming tempest are thus beautifully given by Thomson.—(Winter, l. 118, et seq.)
“When from the pallid sky the sun descends,
With pensive labor draws the flaxen thread,
The circling sea-fowl cleave the flaky clouds. Ocean, unequal press'd, with broken tide And blind commotion heaves; while from the shore, Eat into caverns by the restless wave, And forest-rustling mountain, comes a voice, That solemn-sounding bids the world prepare. Then issues forth the storm with sudden burst, And hurls the whole precipitated air Down in a torrent.” Those tokens which portend the more violent convulsions of the atmosphere, the pelting storm, or the careering tempest, are generally of a decided character, but the symptoms which go before the ordinary fluctuations of the weather can only be dimly conjectured by long experience and sagacious observation. Nothing can be more utterly groundless than the disposition to refer the ordinary changes of the weather to the influence of the moon. But, compared with this, the fancied efficacy of the stellar aspects vanishes into the shadow of a vision. The moon by
its attraction does raise a small tidal wave in the atmosphere, which is indicated by the barometer, but its effect is scarcely perceptible. According to the calculations of Laplace, the joint action of the sun and moon is only capable of producing a tropical wind flowing westward at the rate of about four miles a day, and the effect produced by the conjoint actions of Jupiter and Venus, when nearest the earth, would be a very gentle breeze moving about a foot in fourteen or fifteen days, or about a mile in twenty years. The invisible and perfectly elastic fluid which surrounds the earth is called the atmosphere, or atmospheric air. It appears to consist principally of two distinct expansible fluids, mechanically combined in different proportions: a single portion or atom of oxygen gas being united to three parts by weight, or four by bulk of nitrogen, with a very slight admixture of carbonic acid, perhaps one-thousandth part of the whole. Air was formerly considered as an elementary body, but the analysis of this rare medium is one of the finest discoveries of chemistry. The atmosphere, although apparently so rare and mobile, is nevertheless, capable of presenting great resistance to any obstacles to which it may be opposed. We shall see this more completely illustrated when we describe the phenomena attending hurricanes and other windy storms, but meanwhile it will answer our present purpose to simply refer to its use as a natural agent in propelling vessels by means of sails, and urging the sails of wind mills. Although it is, comparatively speaking, light, and in the ordinary acceptation withoutweight, yet we must not forget that it is now clearly demonstratable that the atmosphere which invests our earth, presses everywhere on its surface with a power of about 15 lbs. to the square inch. The famous Torricellian experiment proves this. It is well known that if the mouth is applied at one end of a small tube, the other end of which is immersed in water, that upon exhausting the air from the tube by the process called suction, the fluid rises swiftly and flows into the mouth; this is a philosophical experiment, but well known to every child. Now, if a person ignorant of the principle that caused the water to rise in the tube, should be asked for an explanation, he might answer