Lake Gaiba is a stretch of water ten miles long, with a narrow mouth opening into the River Paraguay. The lake is surrounded by mountains, clad in luxuriant verdure on the Bolivian side, and standing out in bare, rugged lines on the Brazilian side. The boundary of the two countries cuts the water into two unequal halves. The most prominent of the mountains are now marked upon the exhaustive chart drawn out. Their christening has been a tardy one, for who can tell what ages have passed since they first came into being? Looking at Mount Ray, the highest of these peaks, at sunset, the eye is startled by the strange hues and rich tints there reflected. Frequently we asked ourselves: "Is that the sun's radiance, or are those rocks the fabled 'Cliffs of Opal' men have searched for in vain?" We often sat in a wonder of delight gazing at the scene, until the sun sank out of sight, taking the "opal cliffs" with it, and leaving us only with the dream. On the shores of the lake the beach is covered with golden sand and studded with innumerable little stones, clear as crystal, which scintillate with all the colors of the rainbow. Among these pebbles I found several arrowheads of jasper. In other parts the primeval forest creeps down to the very margin, and the tree-roots bathe in the warm waters. Looking across the quivering heat-haze, the eye rests upon palms of many varieties, and giant trees covered with orchids and parasites, the sight of which would completely intoxicate the horticulturist. Butterflies, gorgeous in all the colors of the rainbow, flit from flower to flower; and monkeys, with curiously human faces, stare at the stranger from the tree-tops. White cotton trees, tamarinds, and strangely shaped fruits grow everywhere, and round about all are entwined festoons of trailing creepers, or the loveliest of _scarlet_ mistletoe, in which humming-birds build their nests. Blue macaws, parrots, and a thousand other birds fly to and fro, and the black fire-bird darts across the sky, making lightning with every flutter of his wings, which, underneath, are painted a bright, vivid red. Serpents of all colors and sizes creep silently in the undergrowth, or hang from the branches of the trees, their emerald eyes ever on the alert; and the broad-winged eagle soars above all, conscious of his majesty. Here and there the coast is broken by silent streams flowing into the lake from the unexplored regions beyond. These _riachos_ are covered with lotus leaves and flowers, and also the Victoria Regia in all its gorgeous beauty. Papyrusa, reeds and aquatic plants of all descriptions grow on the banks of the streams, making a home for the white stork or whiter _garza_. Looking into the clear warm waters you see little golden and red fishes, and on the bed of the stream shells of pearl.