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Which extend over the broadest region or greatest range of
Are the trade-wind regions widest on the Atlantic or Pacific ?
On the coast of what part of North America do periodical
Do the hurricanes in various parts of the world generally have
Does the region of the northern hemisphere in which south-
How much of the distance around the globe is it north of the
Note. - The specific causes of many of the facts to which attention is
In which of these hemispheres is the course of the isothermal
In what ocean do the isotherms of the north temperate latitudes
Which sides, then, are the warmer within these limits? We
warmer than that of North America, in the same latitudes, bor. dering the Pacific !
Is any part of the western coast of Europe obstructed in winter
From the irregularity in the course of the isothermal lines in
Which of the three great oceans has the widest space inclosed
Do the isotherms extend farthest from the equator, on the
Questions. 436. What are the Etesian winds ? Explain how they are caused. When
* 'Eros, a year, a season
breezes produced ? 439. How wide is the Zone of Calms ? caused ? Describe them. 435. Where do these breezes prevail? How are regular inland and where do the nortes blow? 437. How are land and sex breezes supposed to be
cabins. by violent storms. breeze commences. effort the crew succeed in cutting through the remaining ropes, and the ship A loud crack! a second, and the mainmast goes overboard! By a violent which carried her out. frightful roar; with a shriek the sails are torn asunder, and fy in ribbons ! flapping disma!ly upon the spars. Suddenly the storm bursts over with and rocks upon the irregular waves, but the sail still hangs against the mast, whence a streak of foam advances over the black ocean. The ship sways the wild, murderous glance of despair. wall to the eastward; a low, shrill pipe resounds from the distance, from a peculiar coppery redness; and with the advancing night arises a black
440. “The sun sinks below the horizon, the evening sky is illumined by tongue to the palate. Each man looks upon his companion in suffering with spot. The store of water is exhausted. Glowing thirst glues the parched The deck burns through the soles of the shoes.
A fortnight has the ruler of the sea lain immovable in the same glow through and through the narrow space in which the men are inclosed. lies bound on the crystal fluid. The rays of the sun, falling perpendicularly, glassy surface. The ship, hitherto speeding onward with a bird-like flight, little while, and at last drops entirely. Around extends the sea, an endless brought them thus far, becomes weaker and weaker ; at first it ceases for a Sooner or later, according to the time of year, the favoring wind which had the equator in the midst of the Atlantic Ocean, anxious fear seizes the crew. 60, but varies with the seasons from 90 to 10%. It is frequently interrupted
“When the vessel on its voyage to the south approaches 439. The Zone of Calms, represented on the map, has a breadth of about snow-clad mountains, marshes, or sandy deserts. sphere, affected by the radiating properties of neighboring situations, are produced by changes in the density of the atmoinland breezes experienced in the morning and evening, in some nean and in the East and West India Islands. The regular from land. They are also very perceptible in the Mediterraof Malabar, where it is said that their influence is felt 60 miles
438. These breezes are particularly strong along the coast during the night, and dies away in the morning when the seabreeze from the land, which blows freshly from off the coast o'clock it begins to subside, and is succeeded at evening by a the day, when it becomes a brisk gale; after two or three the shore, but gradually increasing in force till the middle of unequal heating of the land and sea. nine o'clock in the morning—at first blowing gently toward within the tropics, a breeze from the sea daily occurs about
437. Land and sea breezes are supposed to be caused by the the Brazil coast, from N. E. in the spring, and S. E. in autumn. September to March in the Gulf of Mexico. They occur also on Periodical currents, called nortes, or north-winds, blow from rope to Africa in summer is much quicker than the autumn. colder atmosphere of the north. Hence the passage from Euan almost vertical sun, and currents are created from the and flints, becomes very highly heated under the influence of of the Mediterranean, deprived of water, and composed of sand only throughout the day. The immense desert of Sahara, south ward the middle of July, about nine i- the morning, and continue terranean, particularly the Levant, where they commence to from the northeast for about six weeks throughout the Medi
436. The Etesian winas* are periodical winds which blow returning by a monsoon blowing in an opposite direction to that them a ship is frequently wafted to a distant port, and aided in
A stifling vapor fills the On the coasts and islands
now flies over the ocean—now borne high upon the backs of the waves-now the southern hemisphere their rotation is direct, conformable hurled down into the depths, so that every seam cracks and groans as though to the hands of a watch. it would part asunder. The thunder rolls unceasingly; continuous light
445. There are three well-known hurricane regions--the ning darts through the agitated atmosphere ; the rain falls in streams instead of drops. Ten times the sailors give themselves up for lost, when the
West Indies, the Indian Ocean, and the China Sea. The quaking bark falls into the trough of the sea, and as many times does it rise general course of the West Indian hurricanes is from the over the waves again.
Leeward Islands N. W., passing around the shores of the Gulf 441. “At last the storm lulls; single shocks follow, always at longer of Mexico or across it, then following the Gulf Stream and intervals ; the waves become smoother, and when the consoling sun rises terminating in the Atlantic, or exhausting their fury in the Mirror-like the endless surface again expands, and in eight days is the
United States. From October 3, 1780, to August 25, 1837, store of collected water exhausted ; and again the silent specters creep inclusive, 38 hurricanes occurred in this region in the following about and turn murderous looks upon each other. A new storm, and a new months: in June, 1; July, 4; August, 13; September, 10; calm, and so in frightful alternation, until at last the ship is driven into October, 8; exclusive of two, the months of which have not the region of the peaceful trade-wind on the other side of the equator.
been recorded. Thus they are very rare in June, and most Hundreds of ships have gone down in storms here ; hundreds lost their crews by the most frightful of deaths,—that of thirst ; and those who frequent in August. The only instance in June occurred in have passed the fearful region of calms, turn in earnest worship to Heaven 1831, when Trinidad, Tobago, and Grenada were devastated, with thanks for their new-won life."O
before supposed to be exempt from hurricanes.
446. The hurricanes of the Indian Ocean come from the N. E., near Sumatra and Java, and travel to the S. W. toward
Rodriguez and the Mauritius. They occur chiefly from DeLESSON VI.
cember to April, the hot season in that hemisphere; are very
rare in November and May; and are quite unknown during HURRICANES.
the other months of the year. 442. The terms hurricane, whirlwind, water-spot, land-spout,
447. In the China Sea, hurricanes, there styled typhoons, sand-pillar, tornado, white squall, pampero, etc., have been ap- range from 10° to 30° N. They occur from June to November,
after an interval of three or four years.
plied to rotary movements of the atmosphere in different parts of the world.
443. Hurricanes are revolving storms which occur chiefly in the West Indies and in the Indian Ocean. Of a similar kind are the typhoons in the China Sea. These circulating movements occupy a space from 50 to 500 miles in diameter. They revolve the more rapidly the nearer the center, up to a certain or evaporated, being converted by the heat into invisible vapor, distance, within which there is a calm.
and diffused through the air. In like manner evaporation 444. The center of rotation advances steadily along a defi- transpires upon a grand scale from the great collections of nite line upon the globe, with a velocity varying from 2 to 30 water on the earth's surface, the oceans, lakes, and rivers, as or 40 miles per hour. It is a remarkable fact, that in the same well as from moist ground. It is subject to diurnal and annual hemisphere these whirling storms always revolve the same variations. way, but that this direction is opposite in opposite hemi- 449. The quantity of vapor diffused through the air is least spheres. In the northern hemisphere their rotation is retro- | in the morning before sunrise. As the temperature rises with grade, or in a direction opposite to the hands of a watch. In the ascent of the sun, evaporation increases. The heat of mid
Questions. ---412. What terms have been applied to the rotary movements of the atmosphere ? 448. What are hurricanes ? What space do these circulating Inovements occupy? Where do they revolve the more rapidly? 444. What is the velocity of the center of rotation? What is a remarkable fact? What is the rotation of the storms in the northern hemisphere? In the southern hemisphere? 445. Which are the three wellknown hurricane regions ?
Questions.- What is the general course of the West Indian hurricanes ? When are hurricanes in this region most rare, and when most frequent? 446. Describe the hurricanes of the Indian Ocean. When do they chiefly occur ? 447. What is said of the typhoong? When and how often do they occur? 448. What will happen if we place a vessel of water in the open air on a warm day? Where does evaporation transpire on a grand scale ? 449. When is the quantity of vapor diffused through the air the least ? When does evaporation increase? What does The heat of mid-day cause? In what month is the quantity of vapor at its minimum, and in what at its maximum ?
arise from the warm waters of the Gulf Stream, which flow to that locality, the temperature of which is much higher than that of the saturated air.
day causes the vapors to rise into the upper regions, and hence the greatest degree of dryness is generally felt during the daytime, though evaporation is then going on most rapidly. In January the quantity of vapor, like the mean temperature of the air, is at its minimum: it increases from that period, and in July attains its maximum; it then decreases to the end
of the year.
450. The moisture in the atmosphere is an element on which the life of plants and animals as much depends as on temperature. The healthfulness of climate is greatly influenced by the dryness or humidity of the atmosphere. As resulting from the action of heat on water, the quantity of vapor diminishes with the temperature from the equator to the poles. It decreases also as we pass from coasts into the interior of continents. This rule is confirmed in the interior of the United States, in the middle of the plains of the Orinoco, in the steppes of Si
456. Soon after sunset, in calm and clear weather, mists are frequently beria, the deserts of Asia and Africa, and the central parts
formed over the beds of lakes and rivers, while the adjacent land is free
from them. This arises from the land more rapidly losing its heat by raof Australia. In the temperate zone, in general, the annual
diation than the lake or river. The air over the land necessarily becomes evaporation is estimated at between 36 and 37 inches of water. the coldest ; and when the situation of the ground is such as to bring the In the torrid zone, at Guadaloupe, it has been found to amount cold air of the land over the warmer water, a fog confined to its expanse to 97 inches, and at Cumana to 100 inches.
451. The air is only capable of receiving a certain quantity 457. Dew is formed by the gradual condensation of the vaof vapor. Its capacity depends upon its temperature, and is pors
of the atmosphere. After sunset in summer, when the invariable in its extent at the same temperature. According to great diurnal evaporation has filled the air with moisture, and Professor Leslie, air at the freezing point is capable of holding the earth is gradually cooled by radiation under a clear sky, moisture equal to the 160th part of its own weight; at the the atmosphere in contact with the surface is chilled, and has temperature of 59°, the 80th part; at that of 86°, the 40th its capacity to retain the aqueous vapors lessened, which are part; at 113°, the 20th part; and at that of 140°, the 10th part. gradually and gently deposited in the form of fluid drops,
452. When a volume of air contains as much aqueous vapor called dew. In some countries dew supplies the place of rain. as at its particular temperature it is capable of receiving, it is In Palestine and western Asia in general, where showers are then said to be at the point of saturation, being as humid as unknown for several months in succession, the dew formed at can be. If the temperature then rises, it will be capable of re- night moistens the earth and sustains the vegetation, being ceiving more; but if it falls, some of the contained vapor will often so abundant as completely to saturate the tents, baggage, be rejected, and become visible as mist. Thus the effect of a and clothing of travelers exposed to it. change of temperature upon a saturated volume of air is anal- 458. As all objects have not the same capacity for radiating ogous to that of the hand relaxing or tightening its grasp on heat, some cooling much more rapidly than others, we frea piece of imbibing sponge.
quently find certain bodies densely covered with dew, as grass 453. It has been frequently observed that the summits of and leaves, while the bare grounds, metals, stones, and wood some mountains are constantly covered with clouds. The are comparatively dry. A thermometer laid on a grass-plot on formation of such clouds may be thus explained: The winds, a cloudless night has been upward of 16° lower than another laden with vapor from lower and warmer districts, in passing laid at the same time on a gravel walk. Hence there has been over such ranges are forced up into a colder region, where a much more copious deposition of dew on the grass than on they are obliged to part with a portion of the vapor, which the walk,—the herbs needing the nourishment thus receiving thus forms a cloudy state of the atmosphere.
it in preference to the bare soil—a striking evidence of an all454. Mists and fogs are formed when the air is saturated, wise Being operating in the economy of nature.* and generally when the moist soil, or the water of lakes and rivers is warmer than the air, the vapors of which are immediately condensed. In like manner the vapor of the air breathed from our mouths in winter becomes condensed and visible.
LESSON VIII. Mists differ in no respect from clouds except in position, being on the surface of the earth, instead of being suspended at a
CLOUDS. height in the atmosphere.
459. Clouds are masses of visible vapor like mists, floating 455. The thick mists which prevail in the neighborhood of Newfoundland in the atmosphere at a distance from the surface of the earth.
Questions.—450. What is said of the moisture in the atmosphere? How does the quantiiy of vapor diminish? Annual evaporation in the temperate zone? In the torrid zone? 451. What is said of the capacity of air for receiving vapor? Upon what does it depend ? Give its capacity at different states of temperature, 452. When is a volume of air said to be at the point of saturation ? 453. What has been frequently observed? How may the formation of such clouds be explained ? 454, When are mists and fogs formed? How do mists differ from clouds ?
Questions.-455. Origin of the mists which prevail in the neighborhood of Newfoundland ? 456. Explain why mists are frequently formed over the beds of lakes and rivers while the adjacent land is free from them. 457. How is dew formed ? Explain particularly the operation of its formation. What is said of the dews of Palestine and western Asia ? 458. Why does dew collect more on some bodies than others? 459. What are clouds ? What is said of them ?
* Rev, Thomas Milner,
They exhibit an endlessly diversified outline, a remarkably | fibers have pointed in a particular direction for any length varying density, and appear at different elevations. The dense of time, the gale may be expected to blow from that quarter.
463. Cumulus-Stackencloud. Fig. 3.- This form of cloud
zontal base and increasing upward. Hence the names cumulus,
464. Cumuli are indications of fine weather. They begin to
465. Stratus—Fallcloud. Fig. 5.—This cloud consists of horizontal bands near the surface of the earth. It belongs to the night, forming at sunset and disappearing at sunrise. This class of clouds comprehends all those fogs and creeping mists which sometimes spread like a mantle over the surface of the valleys, plains, lakes, and rivers.
466. To the above primary varieties three transition or com
posite forms are added. Cirrocumulus--Sondercloud. Fig. 2. 1, 1. Cirrus. 3. Cumulus. 5. Stratus. 2 2. Cirro-Cumulus. 4. Nimbus.
This name designates the feathery accumulated cloud, familclouds are usually formed toward noon, when the vapors are iarly known as fleecy, intermediate between cirrus and cumulus. raised up by the ascending currents of air, and then condensed by the lower temperature of the upper regions.
460. Though clouds are generally composed of vapor, they may consist of frozen particles. In winter, during severe cold, we can often observe that the vapors which rise are composed of brilliant needles, that glisten in the sun and resemble small flakes of snow. The same thing must take place in the higher regions of the atmosphere. There exist, therefore, snowclouds and clouds of vapor of water.
461. Notwithstanding the varied aspect of clouds, they may be arranged into three principal classes—the cirrus, the cumulus, and the stratus.
462. Cirrus— Curlcloud. Fig. 1.—The cirrus (the cat's-tail of sailors) is composed of thin filaments, variously disposed, in the form of woolly hair, a crest of feathers, or slender net-work. The cirri appear in the higher regions of the atmosphere, and are the most elevated of the clouds. Viewed from the summits of high mountains, while the traveler looks down upon other forms of clouds, he beholds these still above him, and apparently at as great a distance as when seen from the plains. The appearance of true cirrus, or curlcloud, is supposed to
NIGHT SCENE, TICONDEROGA. indicate variable weather; when most conspicuous and abun- It consists of small patches, arranged in extensive beds, the dant, to presage high winds and rain; and when the streaming component parts being quite distinct or asunder. Cirrostratus
Questions.—460. Of what are clouds composed? What two kinds ? 461. Into what three Questions.-464. What do cumuli indicate ? Describe their successive changes during principal classes may clouds be arranged ? 462. Describe the cirrus or curlcloud. What the day. 465. Of what does the stratus or fallcloud consist? When does it prevail? What is said of the height of the cirri? What is the cirrus supposed to indicate ? 463. Describe does this class of clouds comprehend? 466. Describe the cirrocumulus or sondercloud. the cumulus or stackencloud. Of what does it consist ?
What other composite forms are mentioned ?
- Wanecloved and Cumulostratus-Traincloud (not repre- Sierre Leone, Guinea.... lat. 90 N. is equal to 189 inches sented in the cut), are combinations,—the former of the cirrus
Island of Grenada, West Indies ..
108 Havana, Cuba.
90 and stratus, and the latter of the cumulus and stratus.
81 467. Nimbus-Raincloud. Fig. 4.-Any of the preceding
68 modifications may pass over into the actual rainy clouds, first Charleston, South Carolina..
47 exhibiting a great increase of density, and a bluish-black tone Rome
24 of color, then putting on a lighter shade, or gray obscurity, and
17 becoming fringed at the edges.
13 468. Clouds are generally higher within the tropics than in
Annual quantity of rain within the tropics of the New World. .115 inchon the temperate zones; and in the temperate zones they are Annual quantity within the tropics of the Old World........ 76 commonly higher in summer than in winter. The cirri are Average for the tropics generally ...
951 the highest clouds. They are supposed to range from three
Annual quantity of rain in the temperate zones of the New
37 to five miles above the level of the earth. Kaemtz states that
In the temperate zones of the Old World (Europe)..
314 during a stay of eleven weeks within sight of the Finsteraar
Temperate zones generally...
344 horn, upward of 14,000 feet high, he never obs -rved any 473. Although the amount of rain is greater within the tropics than in cirri below the summit of the mountain. It is highly probable the temperate zones, yet the number of rainy days is less, because two seathat they consist of flakes of snow.
sons divide the year-wet and dry ; and during the dry season entire months frequently pass away without a drop falling or a cloud being seen. In the temperate zones, also, in passing from the tropics to the polar circles, tho number of rainy days increases, although the intensity of rain diminishes. Annual number of rainy days in North of Syria....
54 LESSON IX.
Straits of Gibraltar..
68 RAIN. :
Plains of Lombardy.
90 Buda, Hungary...
112 469. Rain is water, which, originally taken up into the at
Plains of Germany.
141 mosphere in the state of vapor, is returned to the earth in the
England and West France .152 form of liquid drops. It is produced by the continued con
St. Petersburg. densation of vapor. Rain may begin to fall, and yet not reach
.170 the ground, being resolved into invisible vapor on arriving at
East of Ireland .
..208 strata of air removed from the point of saturation. For the same reason, rain-drops may become smaller in their descent, a portion being evaporated, and less rain arrive at the earth's surface than at a certain height above it. Usually the drops increase in their fall, bringing with them the low temperature of the upper regions.
470. The following are examples of very extraordinary showers :
1841.–June 4, at Cuiseaux, a small town in the valley of the Saone, there fell about 11 inches in 68 hours.
APPROACHING STORM. At Cayenne, Admiral Roussin collected 10 inches in 10 hours. 471. Rain is very unequally distributed over the regions of
474. Countries situated in the vicinity of the sea receive, as we have re
marked, a larger amount of rain than those inland. This is exemplified in the globe. 1. The average annual quantity of rain is the great
the interior of the United States, of the Llanos of the Orinoco, of the Sibeest in tropical climates, and diminishes as we recede from the
rian steppes, of Australia, and on comparing the amount of precipitation in equator to the poles. 2. It decreases as we pass from maritime inland and maritime countries. It declines from an annual fall of between to inland countries, because the land supplies a less quantity of
30 and 35 inches on the shores of Great Britain and France to from 15 to vapor than the sea. 3. More rain falls in mountainous than in
13 inches as the borders of Asia are approached. Mountains produce low level districts, lofty heights arresting the clouds, and pro
several exceptions to this rule. The annual number of rainy days de
creases also with the increased distance from the sea. moting the condensation of vapor by their cold summits. 4.
West coast of France...
152 days. The result of experiment shows that a greater amount of rain Interior of France
.147 falls while the sun is below than when above the horizon.
Kasan, Plains of the Volga .
90 472. The diminution of the average annual quantity of rain from the Interior of Siberia......
60 equator to the poles, appears from the following table :
475. The annual fall of rain in mountainous districts, as compared with San Luis de Maranhao..
.lat. 3° S. is equal to 276 inches. that of low and level countries, is sometimes very striking. At KeswickParimaribo, Guiana.
11 60 N.
a mountainous district in England -- the annual average depth of rain is 67
Questions.-467. Change to the nimbus or rain-clənd? 468. What is the comparative height of clouds in different zones and grasons? Height of the cirri? What does Kaemtz state? 469. What is rain? How produced ? 470. Give examples of very extraordinary showers. 471. What is said of the uni qual distribution of rain? Where is the average anonal quantity ihe greatest? Where does it decrease ? What is observed of mountainous distri.s? What does the result of experiment show? 472. What is the annual quantity of rain in different places? The annual quantity within the Tropics of the Old World ? or the New World ? Average for the Tropics generally? Annual quantity in the Temperate Zones of the New World ?
Questions. In the Temperate Zones of the Old World ? . In the Temperate Zones general'y? 478. Wbere is the number of rainy days less than in the Temperate Zones, and why? What is observed in p:issing from the Tropics to the polar circles ? State the annual number of rainy days in different places ? 474. What is said of countries situated in the vicinity of the sea ? How is this exemplified ? With what does the annual number of rainy day, decrease ? Illustrate. 475. What facts illustrate the difference between mountainous districts and low and level countries witb rospect to the fall of rain? What is remarked of the description of Judex by the shared writer 1