The people believe that every five years the Orinoco rises three feet
higher than common; but the idea of this cycle does not rest on any
precise measures. We know by the testimony of antiquity, that the
oscillations of the Nile have been sensibly the same with respect to
their height and duration for thousands of years; which is a proof,
well worthy of attention, that the mean state of the humidity and the
temperature does not vary in that vast basin. Will this constancy in
physical phenomena, this equilibrium of the elements, be preserved in
the New World also after some ages of cultivation? I think we may
reply in the affirmative; for the united efforts of man cannot fail to
have an influence on the general causes on which the climate of Guiana
depends.

According to the barometric height of San Fernando de Apure, I find
from that town to the Boca de Navios the slope of the Apure and the
Lower Orinoco to be three inches and a quarter to a nautical mile of
nine hundred and fifty toises.* (* The Apure itself has a slope of
thirteen inches to the mile.) We may be surprised at the strength of
the current in a slope so little perceptible; but I shall remind the
reader on this occasion, that, according to measurements made by order
of Mr. Hastings, the Ganges was found, in a course of sixty miles
(comprising the windings,) to have also only four inches fall to a
mile; that the mean swiftness of this river is, in the seasons of
drought, three miles an hour, and in those of rains six or eight
miles. The strength of the current, therefore, in the Ganges as in the
Orinoco, depends less on the slope of the bed, than on the
accumulation of the higher waters, caused by the abundance of the
rains, and the number of tributary streams. European colonists have
already been settled for two hundred and fifty years on the banks of