und in
many of the storms cited by Colonel Reid. With respect to Mr. Espy's
_cause_ of storms, the experiments of Regnault may be considered as
decisive of the question:--1st, because the specific heat of vapor is so
much less than Espy assumed it to be; and 2d, because the expansion of
air in a free space does not suffer any change of volume by ascending,
except what is due to diminished pressure, and the natural temperature
of that elevation.

INDICATIONS OF A STORM.

In accordance with our theory, the direction and force of the wind in a
storm are due to ascending columns of air, supplied from the upper
portion of the atmospheric stratum beneath the clouds. The commotion
begins at the highest limits of the cirri, and even at greater
elevations. Hence, the hazy appearance of the sky is a legitimate
precursor of the coming gale. As a general thing, the wind will blow (at
the surface) towards the centre of greatest commotion, but it is too
dependent on the ever-varying position and power of temporary nuclei of
disturbance, to be long steady, except when the disturbance is so remote
that its different centres of induction are, as it were, merged into one
common focus. When a vortex is descending, or passing from north to
south, and withal very energetic at the time, the southerly wind (which
may always be considered the principal wind of the storm in this
hemisphere) may blow steadily towards the vortex for three or even four
days. When a vortex is ascending, the induced northerly current will be
comparatively moderate, and be frequently checked by the southerly wind
overblowing the storm, and arriving the day before the vortex which
produced it.

The important point for the navigator, is to know the time of meridian
passage of the vortex, and its latitude at the time of the passage, and
then be guided by the indications of the weather and the state of
barometer. If it commences storming the day before the passage, he may
expect it much worse soon after the passage; and again, if the weather
looks bad when no vortex is near, he may have a steady gale setting
towards a storm, but no storm until the arrival of a vortex. Again, if
the barometer is low the day before the vortex passes, there may be high
barometer to the west, and the passage be attended by no great
commotion, as it requires time for the storm to mature, and consequently
its greatest violence will be to the east. If at the ship the barometer
is high, th