Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/719

Rh CLIMATE.] A M E R I C A (Ml fore, the Woods reach from side to side of the continent. But as we recede from the equator the humidity diminishes rapidly and though the continent becomes narrower to wards the south, the supply of rain falls off in a still greater proportion, and the forests extend over a much smaller space. At the foot of the Andes the forests ex tend to 16 or 18 of S. latitude; on the east coast to 25 or probably 30. K L are the Pampas or open lands of Buenos Ayres, extending on the east side of the Andes from Cape Horn to the latitudes just mentioned. If we divide this region into three parts, the most easterly, refreshed by occasional rains from the Atlantic, is covered with a strong nutritive herbage ; the second, which is drier, dis plays a thin coarse wiry grass ; and the third portion, which extends to the Andes, receiving little or no rain, is nearly a desert : all the three are destitute of timber, but the sur face of the third is dotted with dwarfish shrubs. I is the southern part of Chili. Here the prevailing winds, which ure from the west, coming loaded with the moisture of the Pacific Ocean, produce copious rains to nourish the herbage and the forests. This applies, however, chiefly to the country south of the 35th parallel. From that to Coquimbo, in latitude 30, the wood is scanty. Beyond 50 on the east coast of North America, and 55 or 58 on the west, very little wood grows, in consequence of the rigour of the climate. oderating Great misapprehensions have arisen with regard to the rtuences. climate of America, from comparisons being drawn between the east side of the new continent and the west side of the old. We have already pointed out the influence of winds blowing from the sea in modifying the state of the atmo sphere over the land, both as to heat and humidity. When this circumstance is attended to, and when the east and west sides of the old and the new continents are respectively com pared with one another, the difference is found to be small, and easily accounted for. In the torrid zone, and on the sea-shore, the temperature of both continents is found to be the same, viz., 82; but in the interior the difference is rather in favour of America. There is no counterpart in the New World to the burning heats felt in the plains of Arabia and N. Africa. Even in the western and warmest part of the parched steppes of Caraccas, the hottest known region in America, the temperature of the air during the day is only 98 in the shade, which rises to 112 in the sandy deserts which surround the lied Sea. At Calabozo, farther east in the Llanos, the common temperature of the day is only from 88 to 90; and at sunrise the thermo meter sinks to 80. The basin of the Amazon is shaded with lofty woods; and a cool breeze from the east, a minor branch of the trade wind, ascends the channel of the stream, following all its windings, almost to the foot of the Andes. Hence this region, though under the equator, and visited with almost constant rains, is neither excessively hot nor unhealthy. Brazil, and the vast country extending west ward from it between the Plata and the Amazon, is an uneven table-land, blest with an equable climate. At Rio Janeiro, which stands low, and is exposed to a heat comparatively great, the temperature in summer varies from 68 to 82 Fahr., and the mean is only about 74. Farther north, and in the interior, the Indians find it necessary to keep fires in their huts; and in the country near the sources of the Paraguay, hoar-frost is seen on the hills during the colder months, and the mean tem perature of the year falls below 65 or 67. On the de clivities of the Andes, and on the high plains of Upper Peru, the heats are so moderate that the plants of Italy, France, and Germany come to maturity. Lower Peru, though a sandy desert, enjoys a wonderful degree of cool ness, owing to the fogs which intercept the solar rays. At Lima, which is 540 feet above the sea, the temperature vr.ies from 53 to 82, but the mean for the whole year is only 72. In the plains of La Plata the mean temperature of the year is very nearly the same as at the corresponding north latitudes on the east side of the Atlantic. At Buenos Ayres, for instance, the mean annual heat is 19 7 of the centigrade thermometer (68 Fahr.), while that of places on the same parallel in the Old World is 19 S. The range of temperature is probably greater in the basin of the Plata; but as we advance southwards, the diminishing breadth of the continent makes the climate approximate to that of an island, and the extremes of course approach each other. In the Strait of Magalhaens the temperature of the warmest month does not exceed 43 or 46; and snow falls almost daily in the middle of winter, though the latitude corre sponds with that of England. But the inference drawn from this, that the climate is unmatched for severity, is by no means just, for the winter at Staten Island is milder than in London. In point of fact, the climate of Patagonia is absolutely colder than that of places in the same latitude in Europe; but the difference lies chiefly in the very low temperature of the summer. This peculiarity no doubt results chiefly from the greater coolness of the sea in the southern hemisphere; for beyond the parallel of 48, the difference of temperature in the North and South Atlantic amounts, according to Humboldt, to 10 or 12 of Fahren heit s scale. If we push our researches a step farther, and inquire what is the cause of the great warmth of the Northern Sea, we shall be forced to admit that a very satisfactory answer cannot be given. Something may be due to the influence of the Gulf Stream, a minute branch of which is supposed to carry the waters of the torrid zone to the shores of Shetland and Norway; but such an agent seems too trifling to account for the phenomenon. The sum, then, of the peculiar qualities which distinguish the climate of South America may be briefly stated. Near the equator the new continent is perhaps more humid than the old; and within the tropics generally, owing to its vast forests, the absence of sandy deserts, and the elevation of the soil, it is cooler. Beyond the tropics the heat is nearly the same in the south temperate zone of America and the northern one of the old continent, till we ascend to the latitude of Cape Horn, where we have cold summers and a very limited range of the thermometer. The mountain ranges of North America form two widely Highlai distant highland regions, separated from each other by the of N. vast interior plain, which contains, in its southern slope, Amenc: the Mississippi with all its tributaries, and the other rivers flowing into the Gulf of Mexico, while its northern part contains the great fresh-water lakes, and many rivers taking a northward course to Hudson s Bay or to the Arctic seas. The watershed of this plain, dividing the streams that run into the Missouri and Mississippi from those communicating with the Saskatchewan, with Lake Winnipeg, and with Lake Superior, is along a line from west to east nearly coinciding with the 48th parallel of latitude, and has a mean elevation of 1500 feet. Along the whole of the western side, from near the mouth of the Mackenzie in the Arctic Ocean, and from Alaska on the Pacific shore, to the Isthmus of Nicaragua and Panama, that is, across 60 of latitude from north to south, extends with a grand double curve the continuous length of the Rocky Mountains, and others which prolong the line, having a position in North America similar to that of the Andes in South America, and shutting off, in some parts, a comparatively narrow portion of the con tinent, with the Pacific shore, from the great central plain. But several minor ranges, branching off or confronting the principal mountain-ridge or backbone of North America, enclose large spaces of a table-land, traversed by the Columbia, the Fraser, and the Colorado rivers, with those which join them, and holding the Great Salt Lake of