between the elevation and depression is considerable
within the tropics, where Humboldt tells us the hour of the day can be
known by the height of the barometer, and it decreases toward the poles.
At 4 A.M. it is then at one of its minima, and rises till 10 o'clock.

At, or about the same period, and sometimes when the barometer is falling,
and previous thereto, there is a tendency to fog in localities subject to
that condensation. This tendency is sometimes observed at the other
barometric minimum, late in the afternoon or early in the evening, but
less frequently. The tendency to fog condensation is greatest in this
country about the morning minimum. It seems to be owing to the influence
of the earth; it is confined to the surface atmosphere, and is apparently
produced by the inductive agency of the negative electricity of the earth.
It disappears, whether it be high or low fog, about the time when the
barometer attains its morning maximum, or about 10 A.M.

At about that period, when there has been fog, or earlier, when there has
not, and sometimes as early as 8 A.M., there is a tendency to trade
condensation--cirrus in mid-winter, and a cumulus in mid-summer, and,
during the intermediate time, a tendency to cirro-stratus, partaking more
or less of the character of one or the other, according to the season.

Temperature, in summer, commences its diurnal elevation about 4 A.M.,
also, and rises till about 2 P.M. From that time it falls with very little
variation till 4 o'clock the next morning. It has but one maximum and one
minimum in the twenty-four hours.

As the morning barometric maximum approaches, and the heat increases the
magnetic activity, condensation in the trade appears, or induced
condensation in the upper portion of the surface atmosphere, that portion
near the earth is affected and attracted--and the "wind rises," according
to the locality, the season, and the activity of the condensation. The
tendency to blow increases with the tendency to trade and cumulus
condensation, and continues till toward night, when it gradually dies
away, unless there be a storm approaching. As the heat increases, and
stimulates magnetism into activity, the magnetic needle commences moving
to the west, its regular diurnal variation, and continues to do so until
about 2 P.M., when it commences returning to the east, and so continues to
return until 10 P.M., when it moves west again until 2 A.M., and from
thence to the east,