LEAVE MAN ACS. 349 



lowest ebb. Presently, however, the rains on the table-lands 

 of Guiana, and on the northern spurs of the Andes, where 

 the rainy season prevails chiefly in February and March, 

 repeat the same process in their turn. During April and 

 May the northern tributaries are rising, and they reach 

 their maximum in June. Thus, at the end of June, when 

 the southern rivers have already fallen considerably, the 

 northern rivers are at their flood-tide. The Rio Negro, for 

 instance, rises at Manaos to about forty-five feet above its 

 lowest level. This mass of water from the north now presses 

 against that in the centre, and bears it southward again. 

 The rainy season along the course of the Amazons is from 

 December till March, corresponding very nearly, in the time 

 of the year and in duration, with our winter. It must he 

 remembered that the valley of the Amazons is not a valley 

 in the ordinary sense, bordered by walls or banks enclosing 

 the waters which flow between. It is, on the contrary, a 

 plain some seven or eight hundred miles wide and between 

 two and three thousand miles long, with a slope so slight 

 that it hardly averages more than a foot in ten miles. Be- 

 tween Obydos and the sea-shore, a distance of about eight 

 hundred miles, the fall is only forty-five feet ; between Taba- 

 tinga and the sea-shore, a distance of more than two thou- 

 sand miles in a straight line, the fall is about two hundred 

 feet. The impression to the eye is, therefore, that of an 

 absolute plain ; and the flow of the water is so gentle that, 

 in many parts of the river, it is hardly perceptible. Never- 

 theless, it has a steady movement eastward, descending the 

 gentle slope of this wide plain, from the Andes to the sea ; 

 this movement, aided by the interflow from the south and 

 north at opposite seasons, presses the bulk of the water to 

 its northernmost reach during our winter months, and to 



