_Use._

At any time when a severe gale or hurricane is expected, the seaman
should at once find the position of his ship on the chart, and place
upon it the graduated point which answers to the direction of the wind
at the time, taking care that the needle is directed to the north, so
that the exterior letters may point on the chart to the respective
points of the compass: this is very essential. This simple process will
at once acquaint the seaman with two important facts relative to the
coming hurricane--his position in the storm, and the direction in
which it is moving.


_Examples._

A captain of a ship in latitude 35° 24' N., longitude 64° 12' W., bound
to the United States, observes the barometer to stand unusually high,
say 30·55 inches: shortly after the mercury begins to fall, at first
slowly and steadily; as the glass falls the wind freshens, and is
noticed to blow with increasing force from the S. so as to threaten a
gale. The position of the ship on the chart is now to be found, and the
graduated point under the letters E. S. is to be placed thereon,
taking care to direct the needle to the north. From these two
circumstances, the falling barometer and the wind blowing from the south
with increasing force, the mariner is aware of this simple fact, that he
is situated in the advancing portion of a body of air which is
proceeding towards the N.E.; and if he turn his face to the N.E. he will
find he is on the right of the axis line, or line cutting the advancing