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ated in these portions of air, divide, collect, and change form, according to the force acting upon them. Water-spouts are usually attended by a thick, black cloud, formed, probably, by the vapor condensed by opposite currents of air meeting. New accessions of vapor often change the form of clouds; also, the dissolving of vapor, or a diminution of their density. Sometimes, probably, a cloud meets with a stratum of air sufficiently warm to dissolve it. In this case, it will vanish by degrees. Different parts of a cloud may be in strata of air of different warmth or density. The cloud will then partly dissolve, and the part dissolved will, perhaps, rise, and become visible in a higher portion of the air, where the heat is not sufficient to render it visible. In the spring, it is often cloudy in the morning, and clear toward noon. The heat of the sun dissolves the moisture, which arose in great quantities from the damp earth of the morning.
Clouds often move in opposite directions. Different portions of air often move in different directions above one another, on account of their being unequally rarefied by heat. They, of course, carry the clouds with them. This may be readily illustrated. If, in cold weather, the door of a warm room be opened a little, and a candle be held near the bottom of the opening, and another near the top, the flame will often be blown in opposite directions. The cold rushes in at the bottom, and the warm air, being lighter, goes out at the top.
The color of clouds depends on the rays of light which they reflect. Dark clouds often precede wind. But, although they are seen before the wind is felt, they are not the cause, but the effect, of the wind. As the wind moves on, it presses upon that portion of the air which has a velocity less than its own, and by this pressure, and, perhaps, by its greater coldness, condenses the vapor contained in it, and thus forms a cloud. This cloud, being so dense that little or no light can pass through it, appears black. And the degree of darkness depends on the density of the vapor, or, in other words, on the velocity of the wind, and the quantity of water in the portion of air compressed.
The beautiful colors that often adorn the sky at sunset, are caused by the clouds reflecting the sun's light. That redness of the sky in the morning, which is often regarded as the precursor of a storm, probably results from the red rays of the sun passing through the vapor collected in the air. Light is composed of seven different-colored rays, possessing different degrees of force. These may be seen, separate from each other, in the rainbow. Of these, the red rays have the greatest force or momentum. Hence, when the air is very full of vapor, the red rays have sufficient power to penetrate it, while the others have not. Many of the red rays, however, do not come directly from the sun, but are scattered in various directions on striking the vapor, and thus the redness is diffused over a considerable space.
Thunder clouds exhibit an appearance peculiarly striking. To many they are objects of terror. In a greater or less degree, they arrest the attention of alniost every one. These clouds are collections of vapor strongly electrified. They are generally very dense, and very near the earth. Frequently two clouds rise in different parts of the horizon, and move toward each other till they meet, at the same time rising up toward the zenith. When clouds in different electrical states approach each other, or when a strongly electrified cloud approaches near to the earth, the electricity is discharged in vast quantities, and with tremendous violence, thus constituting what is called lightning; while the concussion given to the surrounding air by its force, and the rushing together of the portions of air separated by its motion, causes thunder. This sound, reflected and reverberated among the clouds, produces the long-continued and solemn roll, which forms one of the sublimest characteristics of a thunder-storm.
It is often imagined that lightning always moves toward the earth. But there is reason to suppose that discharges are sometimes made from the earth to the clouds, as well as from the clouds to the earth. It is not difficult to measure the distance of thunder-clouds from the earth. Sound moves at the rate of eleven hundred and forty-two feet in a second; light at the rate of about two hundred thousand miles in a second. The time in which light traverses so small a space as that between a thunder-cloud and any place from which the thunder can be heard, is so short that it need not be estimated. If, then, we multiply the number of seconds between the flash and the thunder by eleven hundred and forty-two, we have the distance
of the cloud in feet. Hence, when a very short time elapses between the flash and the thunder, the cloud is very near.
There is a peculiar sublimity attending thunder-storms in mountainous regions. The traveler among the Andes frequently hears the thunder roll, and sees the lightning flash from the clouds that gather around the hills far beneath him, while around his path, and on the hights above him, the sun is shining with unclouded splendor.
LESSON L X X XIV.
THE BEAUTY OF CLOUDS.
The clouds! the clouds! they are beautiful,
When they sleep on the soft, blue sky,
Their snowy company;
And career o'er the azure plain ;
To scatter their balmy rain.
The clouds! the clouds ! how change their forms
With every passing breath ;
And now they look cold as death. .
From the stir of the noisy crowd,
On the face of a passing cloud.
They come like a band of slaves,
And each in his glory laves.
When the heaven around them glows;
And now with the hue of the rose.
The clouds ! the clouds ! in the starlit sky,
How they float on the light wind's wings ;
In their fickle wanderings !
Now they hide the deep blue firmament:
Now it shows their folds between,
From the jeweled brow of a queen.
To the lightning's flashing eye;
The thunder's majesty.
By the shrill blast's battle song;
From the midst of the dark clouds' throng.
The clouds! the clouds ! my childish days
Are past; my heart is old ;
That never can grow cold :
That time's wave never shrouds;
Miss M. A. BROWNE.
LESSON LX X XV.
THE ZEPHYR'S SOLILOQU Y.
I flit in the days of the joyous Spring,
To fan the heat of his brow away,
I love, when the warrior mails his breast,
When the bright fresh showers have just gone by,
When I go to the cheek where I kissed the rose, And 't is turning as white as the mountain snows, While the eye of beauty must soon be hid Forever beneath its sinking lid, Oh! I'd give my whole self but to spare
gasp, And save her a moment from death's cold grasp! And when she is borne to
alone 'Neath the fresh cut sod, and the church-yard stone, I keep close by her, and do my best To lift the dark pall from the sleeper's breast; And linger behind with the beautiful clay, When friends and kindred have gone their way!
When the babe whose dimples I used to fan,