ails farther down, while at another season of the year these
conditions are reversed. Therefore, though the Amazon has a larger
drainage basin than any other river in the world, and in some parts the
yearly rainfall is 280 inches, there is no very great fluctuation in the
stages of water. The Orinoco River, which flows through Venezuela, and
whose drainage area is largely covered with mountains, has a greater
fluctuation than any other river, the difference between high and low
water amounting to seventy feet.

The River Nile has an annual rise of from fourteen to twenty-six feet.
This river is the sole dependence of the inhabitants of lower Egypt, and
their sustenance depends upon the height to which the river rises; if it
does not rise high enough the agricultural lands are not sufficiently
irrigated, and if it rises too high their crops are destroyed by the
floods. In this section they depend entirely upon the overflow of the
Nile for irrigation, and not upon the rainfall. There is scarcely ever
a rainfall in lower Egypt except about once a year on the coast of the
Mediterranean. After ascending the river for a short distance we come
into an area of no rain for a distance of 1500 miles along the river.
Egypt has a superficial area of about 115,200 square miles, and only
about one-twelfth of this area is in a position to be cultivated.

As there is no rainfall in this region, the sole dependence for
agricultural purposes is from the River Nile when it rises to a
sufficient height to admit of irrigation. The river brings down
quantities of rich earth which during the overflow is deposited, and
thus the agricultural regions are refertilized annually.

The River Nile is what is called a tropical river and is fed by the
rains in upper Egypt caused by the monsoon winds that prevail in that
section of Africa during the summer season, as they do in India. As has
been explained in a former chapter, the monsoon winds blow steadily for
about six months from off the southern ocean. These winds are highly
charged with moisture, which is not precipitated till it strikes the
mountainous regions of the interior. Here the high mountains, which are
often snow-capped, cause a profuse precipitation, which runs off into
the various feeders of the Nile, causing a gradual rise in the river
that reaches the highest point about September of each year. If the
Nile should dry up, or if the annual floods should materially change in
height, it