Some idea may be formed of the vastness of the territory drained by the Amazons from the fact that at the sources of its northern and southern tributaries, the rainy season takes place at opposite times of the year. So wonderful is the length of the stream that, while at the foot of the Andes it begins to rise early in January, the Solimoens swells only in February: and below the Rio Negro the Amazons does not attain its full height before the end of March. The swelling of the river is colossal as itself. In the Solimoens and farther westwards the water rises above forty feet; and Von Martius even saw trees whose trunks bore marks of the previous inundation fifty feet above the height of the stream during the dry season. Then for miles and miles the swelling giant inundates his low banks, and, majestic at all times, becomes terrible in his grandeur when rolling his angry torrents through the wilderness. The largest forest-trees tremble under the pressure of the waters, and trunks, uprooted and carried away by the stream, bear witness to its power. Fishes and alligators now swim where a short while ago the jaguar lay in wait for the tapir, and only a few birds, perching on the highest tree-tops, remain to witness the tumult which disturbs the silence of the woods. When at length the river retires within its usual limits, new islands have been formed in its bed, while others have been swept away; and in many places the banks, undermined by the floods, threaten to crush the passing boat by their fall,--a misfortune which not seldom happens, particularly when high trees come falling headlong down with the banks into the river. The lands flooded to a great depth at every time of high water are called in the language of the country ‘Gapo,’ and are one of the most singular features of the Amazons. They extend hundreds of miles along the river’s course, and vary in width on each side from one to ten or twenty miles. Through the Gapo a person may go by canoe in the wet season, without once entering into the main river. He will pass through small streams, lakes, and swamps, and everywhere around him will stretch out an illimitable waste of waters, but all covered with a lofty virgin forest. For days he will travel through this forest scraping against the trunks of trees, and stooping to pass beneath the leaves of prickly palms now level with the water though raised on stems forty feet high. In this trackless maze the Indian finds his way with unerring certainty, and by slight indications of broken twigs or scraped bark goes on day by day as if travelling on a beaten road.