Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/548

Rh 488 ARGENTINE REPUBLIC Mountains, of the province of Buenos Ayres and those of Cordova, the mountain districts of the country consist of the eastern elope of the gigantic range of the Andes and its branches, which latter make all the north-western part of the country a mountainous region. The great chain of the Andes con sists of a confused mass of broken and contorted strata, piled upon an elevated ridge of granite, through which numerous volcanoes, many of them still active, have ejected vast quantities of lava and scoriae. Along most parts of the great mountain chain there are three subsidiary and more or less parallel ridges, between which fertile valleys are formed in many places, whilst in other parts the separation between them is not very clearly defined. In the north-west the boundary with Bolivia lies along the most eastern of the ridges just mentioned, so that the valleys to the west of it are within that republic, but the boundary with Chili lies along the western ridge, so that the central and eastern ridges, with the fine valleys which lie between them, belong to the Argentine Republic. The great chain of the Andes, as described by Mr Evan Hopkins, who made extensive explorations in various parts of it, is formed of innumerable varieties of granite, gneiss, echists, hornblende, chloritic slates, porphyries, &c., and these rocks alternate with each other in great meridional bands. The crystalline rocks follow no particular order in the alternation. For miles only granite and gneiss are found, and again schist, quartz, gneiss, itc., intervening. i The whole of the crystalline rocks, especially the micaceous , variety, pass insensibly from the crystalline to the laminated structure. We have first the granite base, in which the crystals are somewhat confusedly mixed ; these gradually become arranged upwards into parallel lines, and the rock is then called gneiss ; by degrees the felspar is decomposed, and the mass becomes schistose, with enclosed veins of the predominating element of the compound below. This is the general character of the primary structure of the Andes, and upon it there are many bits of sandstones, limestones, &c., especially on the eastern chain. Mr Dar- 3 The most careful and elaborate researches into the win s re- geological conformation of the country were made by Mr Darwin, who published the results in his work on the geology of South America. He points out evidences of a gradual upheaval of the plains of Patagonia and the Pam pas, to the extent of 400 feet in the southern part of the former, and 100 feet in the latter district. The Pacific and Atlantic Oceans were once connected through what is at present the basin of the Santa Cruz river, in latitude 50 S. This latter district appears to have been upheaved at least 1400 feet before the period of the gradual upheaval above mentioned, as indicated by the present position of gigantic boulders, which have been transported on icebergs 60 and 70 miles from their parent rock. The enormous layers of gravel and sand, on the plains and even on the hills of eastern Patagonia, give evidence of its having at one time formed the bed of an ocean which rolled against the Andes or intervening ranges of moun tains. The characteristic feature of the plains of Patagonia is gravel, whereas that of the Pampean formation, which includes the Chaco, is earth which, according to Mr Darwin s lucid arguments, has been deposited in the form of sand in the estuary of the River Plata, the position of which has been continually changing in consequence of the gradual upheaval of the country. This formation extends to the south-west and north-west from the present estuary, over an area at least 750 miles long and 400 miles broad, and the thickness of the deposit is from 30 to 100 feet. The hills of Tapalquen, Tandil, and Vulcan, composed of unstratified granular quartz, project through the eastern part of this Pampean formation. The higher range of the Sierra Ventana further south is also quartz. South of the searches. Sierra Ventana, for a distance of 380 miles, crystalline rocks are seldom if ever met with on the east coast ; and beyond that a porphyritic formation is found resembling the lowest stratified formation of the Andes. &quot;The highest peaks of the Cordillera, says MrDarvvin, &quot;appear to consist of active, or more commonly, dormant volcanoes such as Tupungato, Maypu, and Aconcagua, which latter stands 23,000 feet above the level of the sea, and many others. The next highest peaks are formed of the gypseous and porphyritic strata, thrown into vertical or highly inclined positions. . . . This grand range has suffered both the most violent dislocations, and slow, though grand, upward and downward movements in mass : I know not whether the spectacle of its immense valleys, with mountain masses of once- liquefied and intrusive rocks now bared and intersected, or whether the view of those plains, composed of shingle and sediment hence derived, which stretch to the borders of the Atlantic Ocean, is best adapted to excite our astonishment at the amount of wear and tear which these mountains have undergone.&quot; We commend Mr Darwin s work to the attention of readers desirous of becoming better acquainted with the geological conformation of the Argentine Republic. The great extent of this country in latitude makes its Climate climate range through all diversities of temperature from that of Northern Europe and Canada to that of Egypt and Arabia. The climate of Southern Patagonia is less intem perate than that of Labrador at the same distance from the equator in the northern hemisphere, but colder than the Atlantic shores of Europe in the same latitude. As the difference of climate in the same latitude in the northern hemisphere is in a great measure attributed to the fact of the warm water from the equatorical regions drifting towards the shores of the north of Europe, whilst the cold water from the Arctic regions is constantly flowing southwards along the coast of Labrador, so also the intermediate nature of the climate of Patagonia is doubtless, in some measure, due to the tendency of the cold water of the Antarctic regions to flow northwards through the cen tral parts of the Atlantic Ocean, as pointed out by Maury&amp;gt; thus throwing the warm water southwards along the coasts of Brazil and Patagonia. Argentine Patagonia might, not inaptly, be termed the Sweden, and Chilian Patagonia the Norway of the southern hemisphere. In the north of Patagonia and the southern part of the province of Buenos Ayres the climate, as regards temperature, resembles that of England ; and northwards of this is the broadest part of the republic, which contains the city of Mendoza in the far west, and Buenos Ayres in the east, and enjoys one of the finest climates in the world, rivalling that of Southern France and Northern Italy. North of this the summer heat becomes too oppressive, and in the extreme north the climate is thoroughly tropical. In some parts of the north west the altitude of the country gives it a cooler climate than that of the Chaco in the same latitude. Along the Argentine slopes of the Andes and the adjacent country the climate is remarkable for its dryness, because the pre valent westerly winds lose the moisture which they bring from the Pacific before crossing the mountains. This peculiarity is most marked in the southern part of the continent, where Chilian Patagonia is deluged with almost incessant rain, whilst Argentine Patagonia is dry and arid. In the east, as at Buenos Ayres, there is more rain, which, with southerly winds and occasional north-westerly storms, is often very heavy. The oppressive humidity which is characteristic of the northerly and north-easterly winds forms the most disagreeable and unhealthy weather experi enced in that part of the country. The climate of Cordova, and also that of some of the more westerly districts, is found very suitable for consumptive patients. The first Europeans who visited the River Plate were a History, party of Spanish explorers in search of a south-west passage to the East Indies. Their leader, Juan Dias de Solis, landed, in 1516, with a few attendants on the north coast