south]
AMERICA
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eastern Brazil, whence the line runs north-west parallel are under the control of the tropical high pressure area of with, but somewhat inland from, the coast of Guiana and the Pacific, and blow from a southerly direction. The Venezuela. In January the heat equator moves to about winds of extra-tropical South America are also chiefly controlled by the tropical anti-cyclonic areas of the South 15° S. in Brazil, while in July it migrates northward be- Atlantic and South Pacific oceans. The former of these yond the limits of the continent. In the former month gives easterly and south-easterly winds in the lower the isotherm of 50° crosses the southernmost extremity of areas latitudes of the eastern portion of the continent, and pieSouth America. In July the isotherm of 30° is found vailing north-westerly winds in the higher latitudes. On somewhat to the south of Cape Horn. Thus the southern summer is not marked by ex- the west coast strong southcessively high mean tempera erly winds blow with tradetures, and the southern winter like regularity north of the is moderate, even in the Pacific anti - cyclone, while higher latitudes. The mean north-westerly winds prevail annual range of temperature to the south of it. The seais very small over all of South sonal migration of these areas America. Over the northern of high pressure involves a portion of the continent, in- corresponding shift in the cluding Peru, Northern wind systems under their Bolivia, and the greater part control. In summer south of Brazil, it is less than 10°. and south-west winds prevail Over a considerable part of along the west coast between this same area the range is 30° and 40° S. lat. South of even less than 5°. South of 40° S. lat. north and norththe tropic and east of the west winds predominate. In Andes the ranges increase to winter the winds between 30° between 30° and 40° in and 40° S. lat. are variable, Wind Pressure. Northern Argentina. In with some calms, while the Distribution of Heat. Chile, on the other hand, they west and north-west winds blow nearer the equator than in summer. In corresponding are less than 20°. The whole of the narrow western coastal latitudes on the east coast there is also a northward extenstrip thus has a very moderate climate. Even in the higher sion of the limits of the north-west winds in winter. In latitudes the winters are very mild; the summers distinctly Argentina north-east, east, and south-east winds increase in cool. Over a portion of the coasts of Guiana and of Eastern Venezuela the mean minimum temperatures average over summer, and north, north-west, and west winds in wintei. In the mountains there are local winds, much influenced 68° The lowest mean minima are found in the interior east by topography. _ of the Andes and south of latitude 20° S. Temperatures Darwin first distinctly emphasized the essential characbelow 32° occur normally every winter over the highlands teristics of South American rainfall. In the latitudes of of the southern interior of Brazil, and thence southward prevailing easterly winds (trades) the eastern ^ j f n. a n a over the interior of Argentina. The highest mean maxima side of the continent and the eastern slopes of (104°) occur in the northern portion of Argentina. All of the Andes are well watered, while the western slopes are the west coast has decidedly lower maxima. . Throughout comparatively dry. In the latitudes of prevailing westerly the mountainous region of South America altitude controls winds the western slopes of the mountains have the most temperature to a marked degree. Places situated far precipitation, while the eastern side is dry. The rainfall above sea-level (e.y., Quito) enjoy “ perpetual spring temis considerable (60-80 inches peratures. On the high peaks, even on the equator, there and over) on the elevated is eternal snow. windward coasts of the conFor the mean of the year the barometric equator crosses tinent (Guiana, South-east South America closely along the line of the geographical Brazil) within the trade-wind equator, running north of it on the western belts, as it is on the eastern Pressure coast. The middle portion of the continent is slopes of the Andes, and over and winds. under the control of the tropical high pressure an extended area along the belt while over the southern extremity the pressure Amazon. Within the southdecreases rapidly towards the south pole. The seasonal east trade belt there is notmigration of sun and heat equator involve a sympathetic ably less rainfall in the lee migration of barometric equator and tropical high pressure of the highlands of Southbelt In January the barometric equator moves south to east Brazil, and the rainfall about lat. 10° in Brazil, while the axisq of the tropical also decreases rapidly in the high pressure belt lies about along 30 S. lat m tbe interior over the more Atlantic, and 35° S. lat. in the Pacific. In u y e southern latitudes of this barometric equator lies along the northern coast and the same belt. The migration axis of the tropical high pressure belt is also farther north of the belt of equatorial calms Rainfal:.. than in January. Seasonal changes and mean monthly and rains over the northern ranges of pressure are slight. The broad northern por ion portion of South America involves a seasonal rainfall oei e of the continent east of the Andes, and noit 0 the greater part of the trade-wind latitudes. There is a tropical high pressure belt, is in the trade-wind zone._ Here dry season while the trade blows, and a rainy season the trades prevail as a rule, except when the sun is most while the equatorial rainy belt is overhead. The coas o nearly overhead. They are then replaced by the equa- Guiana, and Pernambuco and Bahia have winter rams. torial belt of calms and rains, which migrates north and The west coast within the trade-wind latitudes, from ■ south over this portion of the continent, following e lat. to about 30° S., is very dry. It is. shut oft from t e sun. The west coast within the trade-wind latitudes trades, and has southerly, cool, non-rainy winds. Along south of the equator has its own system of winds, which
