LEAVE MANAOS. 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 be 
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 
