« ПредыдущаяПродолжить »
through the plain of ocean, and fixed by the laws of nature though their banks be banks of water, they are almost as sharply defined as if they were of granite masonry. These are constant; there are others periodical, occasioned by periodical winds, tides, &c.; and there are also variable currents caused by melting ice, and other accidents, irregular in their occurrence.
6. You observe that the great world of water serves not only as a home for countless forms of life, but that to us land creatures it serves also as an appara tus for the regulation of our climates. Cold currents come to limit the sun's monarchy, and warm streams flow to melt the icebergs where they travel out of bounds. That is not all, nor nearly all. One characteristic of the works of nature is continually to be recognized. Man makes a beautiful machine, worthy of admiration, in which many wheels and teeth combine, perhaps to make a piece of lace; it will make only lace, and nothing else. The works of nature are incom'parably more simple, and yet there is nothing so minute as to be created for one purpose only. In its way, a blade of grass, or lump of dirt, no less than the great sea, heaps use on use, and proof on proof of a Sublime Intelligence.
xcv. — THE WIND AND RAIN. 1. VAPOR rises from water, and from every moisi body, under the influence of heat. The greater the heat, the more the vapor; but even in winter, from the surface of an ice-field, vapor rises. The greater the heat, the greater the expansion of the vapor. It is the nature of material things to expand under heat, and to contract under cold ; so water does, except in the act of freezing, when, for a beneficent purpose, it is constituted an exception to the rule. Vapor rises freely from lakes, rivers, and moist land ; but most abundantly, of course, it rises from the sea, and nowhere more abundantly than where the sun is hottest. So it rises in the zone El of variable winds and calms, abundant, very much expanded, therefore imperceptible.
2. There comes a breath of colder air on the ascending current; its temperature falls. It had contained as much vapor as it would hold in its warm state; when cooled it will not hold so much; the excess, therefore, must part company, and be condensed again : clouds rapidly form, and as the condensation goes on in this region with immense rapidity, down comes the discarded vapor in the original state of water, out of which it had been raised. Sudden precipitation, and the violent rubbing against
each other, of two air-currents unequally warmed, develop eleo tricity; and then we have thunder and lightning
3. Rain, being elicited by heat from water, will, of course, abound most where the sun is hottest. The averageEl yearly fall of rain between the tropics is ninety-five inches, but in the temperate zone only thirty-five. The greatest rain-fall, however, is precipitated in the shortest time; tropical clouds like to get it over and have done with it. Ninety-five inches fall in eighty days on the equator, while at St. Petersburg the yearly rain-fall is but seventeen inches, spread over one hundred and sixty-nine days. Again, a tropical wet day is not continuously wet. The morning is clear; clouds form about ten o'clock, the rain begins at twelve, and pours till about half-past four; by sunset the clouds are gone, and the night is invariably fine. That is a tropical day during the rainy season.
4. What does the “ rainy season" mean?- At a point twentythree and a half degrees north of the equator, at the tropic of Cancer, the verticale sun appears to stop when it is midsummer with us. As it moves southward, our summer wanes; it crosses the equator, and appears to travel on until it has reached twenty
three and a half degrees on the other side of the line, - the · tropic of Capricorn; then six months have passed; it is mid
winter with us, and midsummer with people in the southern hemisphere. The sun turns back (and the word tropic means the place of turning), retraces its course over the equator, and at the expiration of a twelvemonth is at our tropic again, bringing us summer.
5. Now, the rainy season is produced between the tropics by the powerful action of the sun, wherever it is nearly vertical, in sucking up vast quantities of vapor, which become condensed in the upper colder regions of the atmosphere, er and dash to earth again as rain. The rainy season, therefore, follows the sun. When the sun is at or near the tropic of Cancer, both before and after turning, all places near that tropic have their rainy season; when the sun makes a larger angle with their zenith, it has taken the rainy season with it to another place. It is here obvious that a country between the tropics, and far from each, is passed over by the sun, in its apparent course, at two periods in the same year, with a decided interval between them. Such a country must have, therefore, and does have, two rainy and two dry seasons.
6. The trade-winds, blowing ēquably, do not deposit much of their vapor while still flowing over the Atlantic. These winds ---50 called from being favorable to commerce - blow constantly, one in a north-east and the other in a south-east direction, within about twenty-eight degrees on each side of the equator. Out at sea it seldom rains within the trade-winds; but when they strike the east coast of America rain falls; and the rain-fall on that coast, within the limits of the trade-winds, is notoriously excessive. The chain of the West India Islands stands ready to take in the due season) a full dose; the rain-fall at St. Domingo is one hundred and fifty inches. But the winds, having traversed the breadth of the continent, Et deposit their last clouds on the western flanks of the Andes, and there are portions, accordingly, of the western coast, on which no season will expend a drop of rain.
7. Thus in Peru it rains once, perhaps, in a man's lifetime; and an old man may tell how once, when he was quite a boy, it thundered. The cold Antarctic current, slipping by the Peruvian shores, yields a thick vapor, which serves instead of rain. Upon the table-lander of Mexico, in parts of Guatemala El and California, for the same reason, rain is very rare. But the grandest rainless districts are those occupied by the great desert of Africa, extending westward over portions of Arabia and Persia, to a desert province of the Belooches; districts presently continued in the heart of Asia, over the great desert of Gobi, the table-land of Thibet, El and part of Mongolia. In all these are five or six millions of square miles of land that never taste a shower. Elsewhere the whole bulk of water that falls annually in the shape of rain is calculated at seven hundred and sixty millions of millions of tons.
8. Winds are caused, like currents of the sea, by inequalities of temperature. The hurricane is a remarkable storm wind, peculiar to certain portions of the world. It rarely takes its rise heyond the tropics, and it is the only storm to dread within the region of the trade-winds. In the temperate zone, hurricanes do now and then occur, which, crossing the Atlantic from America, strike the coasts of Europe. It is the nature of a hurricane to travel round and round, as well as forward, very much as a cork. screw travels through a cork, only the circles are all flat, and described by a rotatory wind upon the surface of the water. Hurricanes always travel away from the equator. North of the equator, the great storm, revolving as it comes, rolls from the east towards the west ; inclining from the equator, that is, northward. It always comes in that way'; always describes in its main course the curve of an ellipse. EI
9. The typhoon, a relation of the hurricane's, is of Chinese extraction. It is met with only in the China seas, not so far south as the Island of Mindana'o, nor so far north as Core'a, except upon the eastern borders of Japan'. A typhoon walks abroad not oftener than about once every three or four years; and that is quite often enough. You may believe anything of a typhoon. Robert Fortune says, that when he was at sea in a typhoon, a fish weighing thirty or forty pounds was blowil out of the water, and fell through the skylight into the cabin. That might be believed of a typhoon from a less trustworthy informant.
10. Of local storms and currents, caused, inland or out at sea, by inequalities of temperature, as, for example, by the warm current of the Gulf-stream, we need not particularly speak. The storms and the rain-torrents of Cape Horn, where one hundred and fifty-three inches of rain have been measured in forty-one days, and where the whole year is a rainy season, we can only mention. To the simoom we give a nod of recognition ; verily, that is a penetrating wind which clogs with sand the works of a doublecased gold watch in the waistcoat-pocket of a traveller. We wave our hands likewise to the Italian sirocco, and the Egyptian khamsin, and the dry harmattan; and so our dry talk ends.
11. In equalizing temperature, in wafting clouds over the land, and causing them to break and fall in fertilizing showers, in creating and fostering the art of navigation, by which man is civilized, the winds perform good service. Their pure current washes out the stagnant exhalations from our homes, our fields, our persons ; breaks the ripe seed from the tree, and sows it at a distance from its parent plant, where it may grow in the free air, not overshadowed. Without winds, winter would be one monotony of frost, and summer one monotony of sun. The crisp snow and the woolly clouds, the delightful rustle of the summer forest and the waving of the autumn corn, the glory of the sunset and the wonder of the rainbow,—the world would have wanted these had not the winds been taught to do their Master's bidding, After all, wind and rain prove more than the necessity of carry ing umbrellas.
12. It is raining still ; raining on the just and on the unjust; on the trees, the corn, and the flowers; on the green fields and the river; on the lighthouse bluff and out at sea. It is raining on the graves of some whom we have loved. When it rains dur. ing a mellow summer evening, it is beneficently natural to most of us to think of that, and to give those verdant places their quiet share in the hope and freshness of the morrow. DICKENS.
XCVI. —THE HURRICANE.
1. LORD of the winds! I feel thee nigh,
I know thy breath in the burning sky,
Ånd, lo! on the wing of the heavy gales,
3 He is come! he is come! do ye not behold
His ample robes on the wind unrolled ?
4. Darker — still darker! the whirlwinds bear
The dust of the plains to the middle air :
5. What roar is that? - 't is the rain that breaks
In torrents away from the airy lakes,