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第251章 LAND AND SEA BREEZES

1.In many tropical countries the oppressive heatis modified,and the climate of the sea-shore maderefreshing and healthful,by the regular alternationof winds which come from the sea during the day and from the land during the night.This daily change of wind is due to the fact that the land heats more rapidly and also cools more rapidly than the water.During the heat of the day,the air above the land becomes warmer than that above the sea,and consequently lighter.It therefore rises,or rather it is pushed upwards by the colder air which flows towards the land and takes itsplace.This movement of the air constitutesbreeze.

2.When the sun goes down,the land cools more rapidly than the sea,and the air overlying the land becomes colder and heavier than that above the water.A current of cold air from the land then flows out seawards,pushing aside the warmer air,and forming the land-breeze.

3.Upon the northern coast of Java the phenomenonof daily land and sea breezes is finely developed.Asthe sun rises up out of the sea into the cloudless azuresky,all nature is yet fresh with the dews of night.But as it climbs ever higher,the land-breeze goes to rest.Here and there it still plays over the water,but finally it sinks exhausted,and there is a great calm.The atmosphere becomes clearer under the intense heat,and the gentle swell of the now polished waves reflects the sunshine like a thousand mirrors.

4.All distant objects become distinct,and seem to draw nearer.Small fishing-boats loom up like large vessels.The seaman coasting along the shore is misled by the clearness,and believes that he has been driven towards the land by a current.The planks of the deck burn under his feet;he vainly spreads an awning to shelter himself from the great heat.

5.The sun is near the zenith,and all nature seems to have fallen into a sleep.Yonder,far out on the sea,a darker tint appears on its glassy surface,and again disappears.Once more it returns;it remains,and slowly approaches.It is the welcome sea-breeze;but it may be one or two hours more before it has regularlyset in.Small white clouds appear above the horizon,a symptomof a fresh breeze.Then we feel a coolbreath from the sea,succeeded by others which remain longer,and presently the refreshing sea-breeze has really set in.

6.The air becomes grey with vapour,which envelops the promontories in mist and curtains the mountains with clouds.Objects which seemed near are now apparently removed to a distance,and the sailor is apt to think himself farther from land than he really is.The sea is raised into short broken waves,whose white crests are blown away by the wind.

7.As the sun approaches the horizon,the roll of thunder is heard from the piled-up clouds over the mountains,and the gleam of lightning is seen through the mist.But as the sun sinks,the mist graduallydisappears.The wind and the sea cease their chafingand fretting;soon all is again still.This stillness is pleasant to the feelings.The driving briny sea-breeze had grown wearisome,and the calm is welcome.

8.It is a threatening calm,however.The air above the mountains is still dark and cloudy.The rain falls there in torrents,and the thunderstorm once more rages.Soon the clouds spread seawards from themountains,and the whole sky becomes overcast and threatening.The sailor off the coast knows what to expect:his sails are soon filled by the land-breeze,which will carry him briskly on his way till morning.

9.This alternation of land and sea breezes is most regular and perfect in the regions of calms which are found under the equator and each of the tropics.

when there is no prevailing wind to interfere with the development of those local breezes,the sea-breeze begins to move towards the land about ten in the morning.By three or four in the afternoon it reaches the force of a gale,and stops communication between the shore and ships in the harbour.By sunset,however,the wind has spent its fury,and there is a perfect calm.