e of the storms
the barometer is said to stand fully 2 inches lower than outside the
storm field. The average barometric gradient, near the vortex of the
most violent of these storms, is said to be rather more than 1 inch
in 50 nautical miles. As the center of the storm is approached the
more rapid become the changes of wind, until at length, instead of
its direction altering gradually, as is the case on first entering the
storm field, the wind flies around at once to the opposite point, the
sea meanwhile breaking into mountainous and confused heaps. There are
many instances on record of the wind suddenly falling in the vortex
and the clouds dispersing for a short interval, though the wind soon
blows again with renewed fury.

In the northern hemisphere when the falling barometer and other signs
create suspicion that a typhoon is approaching, facing the wind and
taking 10 or 12 points to the right of it, will give the approximate
bearing of its center. Thus, with the wind NE., the center will
probably be from S. to SSE. of the observer's position. However,
it is difficult to estimate the center of the vortex from any given
point. This partly arises from the uncertainty as to the relation
between the bearing of the center and the direction of the wind,
and greatly from there being no means of knowing whether the storm be
of large or small dimensions. If the barometer falls slowly, and the
weather grows worse only gradually, it is reasonable to suppose that
the storm center is distant; and conversely, with a rapidly falling
barometer and increasing bad weather the center may be supposed to
be approaching dangerously near.

Practical Rules.--When in the region and in the season of revolving
storms, be on the watch for premonitory signs. Constantly observe
and carefully record the barometer.

When on sea and there are indications of a typhoon being near, heave to
and carefully observe and record the changes of the barometer and wind,
so as to find the bearing of the center, and ascertain by the shift of
the wind in which semicircle the vessel is situated. Much will often
depend upon heaving to in time. When, after careful observation, there
is reason to believe that the center of the typhoon is approaching,
the following rules should be followed in determining whether to
remain hove to or not, and the tack on which to remain hove to:

In the northern hemisphere, if the right-hand semicircle, heave to on
the starboard ta