100 AMAZONIA AND LA PLATA. 



ment. On the Brazilian frontier it begins to swell in the month of February, 

 and under the combined action of melting snows and torrential rains it gradu- 

 ally attains a level of 40, 50, or even 56 feet above low-water murk. But the 

 flood waters, diversely influenced by the special inundations of the affluents on 

 both sides, do not reach the lower Amazons till the month of April. In the 

 lower reaches a sort of balance is struck between the waters coming from the 

 north and from the south; the rise of the one corresponds with the fall of the 

 other, so that the Amazons always exceeds the dead level that it would reach if 

 regulated by the action of the Maranon alone. 



Durino- the floods the low islands disappear, the banks are inundated, the 

 scattered lagoons unite with the river and ramify in vast inland seas, driving the 

 animals to take refuge in the forest trees, and the Indians to encamp on rafts 

 moored to the shore. Then, as the stream begins to fall, the waters, returning 

 to their bed, slowly erode the soddened banks by their underwash, and huge 

 masses of earth suddenly give way carrying with them trees, snags, and animals. 

 The islands themselves are often exposed to sudden destruction, and when the 

 protecting barriers of drift-wood yield to the force of the current, a few hours 

 suffice for the swirling waters to sweep them away. Then follow those long pro- 

 cessions of tangled masses of earth, snags, branches, breaking asunder and again 

 uniting, accumulating about the headlands, spreading along the margins, often 

 transporting whole floras of herbaceous plants attached to the roots, whole faunas 

 of birds perched on the boughs or of reptiles coiled round the stems. 



The Amazons Estuaky. 



The Atlantic tides ascend the Amazons as far as Santarem, over 600 miles 

 from Cape do Norte, which is regarded as the terminal point of the estuary. But 

 the salt water does not enter the river, and the only effect of the flow is to check 

 the speed and raise the level of the fluvial current. Even round Mexiana Island 

 in the middle of the gulf, the water is quite fresh and potable at all seasons. 



The ffreat clash between the fluvial and marine waters takes place in the 

 broad part of the estuary where the Amazons, losing in depth, spreads over the 

 lateral shoals and banks. Here the waves, impelled by the marine current and by 

 the Atlantic swell in the direction from east to west, and especially from south- 

 east to north-west, meet the fluvial waters on a rapidly-rising bed. Thus is 

 produced the pororoca, that is, according "to Barbosa Rodrigues, the poroc poroc, or 

 " destroyer." This Amazonian bore exceeds in height all those developed in the 

 Seine, Ganges, Yangtze, or elsewhere. Its terrible roar is heard at a distance of 

 five or six miles, and the successive waves, the first of which is at times 10 feet 

 high, form a complete barrier from shore to shore across the estuary. Their 

 violence is felt especially about Cape do Norte towards the mouths of the Ara- 

 guary and the Straits of Maraca Island. 



The estuary, which is intersected by the equator, expands between Marajo 

 Island and the Guiana coast to a broad marine inlet, forming that " fresh-water 

 sea " which so astonished Pinzon and other navigators after him. West and 



