The other parallel chains that extend over the table-land in Venezuela and Guiana, though not of great height, are very rugged and often crowned with mural ridges; they are separated by flat savannahs, generally barren in the dry season, but after the rains covered with a carpet of emerald-green grass, often six feet high, mixed with flowers. The vegetation in these countries is beautiful beyond imagination: the regions of the Upper Orinoco and Rio Negro, and of almost all the mountains and banks of rivers in Guiana, are clothed with majestic and impenetrable forests, whose moist and hot recesses are the abode of the singular and beautiful race of the Orchideæ and tangled creepers of many kinds. Although all the mountains of the system of Parima are wild and rugged, they are not high; the inaccessible peak of the Cerro Duida, which rises insulated 7155 feet above the plain of Esmeralda, is the culminating point, and one of the highest mountains in South America east of the Andes. The fine savannahs of the Rupununi were the country of romance in the days of Queen Elizabeth. South of Pacaraime, near an inlet of the river, the far-famed city of Manoa was supposed to stand, the object of the unfortunate expedition of Sir Walter Raleigh; about 11 miles south-west of which is situated the lake Amucu, “the Great Lake with golden banks,”—great only during the periodical floods.[51] On the southern side of the basin of the river Amazons lies the table-land of Brazil, nowhere more than 2500 feet high, which occupies half that empire, together with part of the Argentine republic and Uruguay Orientale. Its form is a triangle, whose apex is at the confluence of the rivers Mamore and Beni, and its base extends, near the shore of the Atlantic, from the mouth of the Rio de la Plata to within three degrees of the equator. It is difficult to define the limits of this vast territory, but some idea may be formed of it by following the direction of the rapids and cataracts of the rivers descending from it to the plains around. Thus, a line drawn from the fall of the river of the Tocantins, in 3° 30ʹ S. latitude, to the cataracts of the Madeira, in the eighth degree of south latitude, will nearly mark its northern boundary; from thence the line would run S.W. to the junction of the Mamore and Beni; then turning to the S.E. along the ridges of mountains called the Cordillera Geral, and Sierra Parecis, it would proceed south to the cataract of the Paraná, called the Sete Quedas, in 24° 30ʹ S. lat.; and lastly from thence, by the great falls of the river Iguassu, to the Morro de Santa Martha, in lat. 28° 40ʹ, south of the island of St. Catherine.