AMAZON 379 of the Ucayali, is by some considered as its source ; but it properly rises in Lake Laurico- cha near the mines of Cerro Pasco. The head waters, under the name of Tunguragua or Upper Maraflon, flow northerly 500 m. in a series of rapids between the Peruvian Cordille- ras, and on reaching the boundary of Ecuador run E. N. E., maintaining this course to their exit under the equator. But the Amazon is a vast river system, rather than one river. More than 350 branches and lesser tributaries unite in the grand trunk of this giant stream. From hit. 3 N. to 19 8., a distance, measured by the windings of the mountain chain, of 2,000 m., there is not a stream that descends the eastern slope of the Andes that does not con- tribute its waters to swell this mighty flood. Besides the Tunguragua, we find on the S. side the Huallaga, rising within a few miles of its source, and having nearly the same course and length ; it is navigable by steamers to Yurima- guas and by canoes to Tingo Maria. About 200 m. below its mouth enters the magnificent Ucayali. This tributary rises near Ouzco, and has a length of about 1,200 m., with an average width for 250 in. above its mouth of half a mile, and a current of 3 m. an hour. A small steamer has ascended 773 m. from Nauta. Several large but little known streams succeed, as the Javari, Jutahi, Telf6, and Purus, the last of which has been ascended 1,800 m. But the largest contributor to the Amazon is the Ma- deira. At its junction it is 2 m. wide and 66 feet deep. Its extreme length is probably 2^000 m., and it is navigable 480 m. Of its affluents, the Beni rises near Lake Titicaca, and the Mamor6 is separated only 15 m. from the source of the Pilcomayo, the largest afflu- ent of the Paraguay. The Tapajos, 1,000 m. long, rises within 20 m. of the head waters of the Paraguay, and is navigable 160 m. above Santarem. East of the Tapajos are the Xingd and Tocantins, navigable about 150 m., the latter of which, however, is an affluent of the Para, and not of the Amazon proper. From the north, the great river receives the Negro, '1,200 m. long. This tributary is of commercial importance, not only because of the rich region through which it flows, but also because it is connected with the Orinoco by the natural canal Cassiquiare. Nearly par- allel to the Negro are the Japura and Putu- mayo, each 1,000 m. long; and further W. flow the Napo and Pastaca, rising in the Quitonian Andes, the former navigable 500 m., the other a torrent. The total length of the Amazon from its source to Para, following the curves, is 2,750 m. If we consider the Ucayali as the head, it will measure 3,000. Lieut. Hern- don estimated its length from the source of the Huallaga at 3,944 m. Though not the longest, the Amazon is the most voluminous river on the globe. The water passing Obidos every second amounts to 500,000 cubic feet, and its freshening influence is perceptible 500 m. from the coast. Some idea of its magnitude may be gained from the fact that 900 m. from its mouth it receives a tributary 2,000 m. long. The usual current is 3 m. an hour. The depth varies from 42 feet in the upper part to 312 at its mouth; at Tabatinga, where it crosses the Brazilian frontier, it is 66 feet. It is deep at the very edge, not having those sloping shores which characterize most streams. At Nauta, 2,300 m. from the sea, it is m. wide; at the entrance of the Madeira it is 3 m. ; below San- tarem it is 10 in. ; and if we include the Para, its mouth is 180 m. wide. The Para river, however, is distinct, and is joined to the Ama- zon by very narrow channels. Like other tropical rivers, the Amazon is subject to pe- riodical inundations. The banks, usually high, are overflowed, and vast tracts are flooded. The rise above the lowest level is between 7 and 8 fathoms. At Ega the rise begins about the close of February. The tide of the ocean is perceptible at Obidos, 450 m. up. The bore, or pororoca, as it is termed by the natives, is a phenomenon worthy of remark. It was well described by La Condamine, more than 100 years ago, in these terms : " During three days before the new and full moons, the period of the highest tides, the sea, instead of occupying six hours to reach its flood, swells to its highest limit in one or two minutes. The noise of this terrible flood is heard five or six miles, and increases as it approaches. Presently you see a liquid promontory, 12 or 15 feet high, fol- lowed by another, and another, and sometimes by a fourth. These watery mountains spread across the whole channel, and advance with a prodigious rapidity, rending and crushing every- thing in their way. Immense trees are instant- ly uprooted by it, and sometimes whole tracts of land are swept away." It is difficult for ves- sels to withstand such a tide, and hence those accustomed to the navigation of the river avail themselves of esperas, or resting places, where their vessels may be sheltered from its vio- lence. Another characteristic feature is the system of back channels joining the tributaries, and the igarapes or canoe paths through the forest. One may go from Santarem 1,000 m. up the Amazon without ever entering it. The water of the upper Amazon and of the Pasta- ca, Huallaga, Tapajos, Xingu, and Tocantins is blue or olive-green ; that of the lower Ama- zon and of the Madeira, Purus, Jutahi, Javari, Ucayali, Napo, Putumayo, and Japura is yel- lowish; of the Negro and Teff6, black. The temperature of the water will average about 80. The river is full of islands and sand bars, and the axis of the channel is constantly changing. A vast amount of sediment is carried into the sea, but there is no delta proper, the Maraj6 and other islands in the great estuary having a rocky base. The immense valley of the Amazon is walled in by the Andes and the highlands of Guiana and Matto Grosso. No other region of equal area has such a remark- ably uniform character, and its geological formation is of deep interest. Scarcely any-
