The Law of Storms / The various phenomena by which their approach can be ascertained with certainty, and practical directions to mariners for the avoidance of their fury, compiled from various sources

by John Ross

THE LAW OF STORMS:

THE VARIOUS PHENOMENA BY WHICH THEIR
APPROACH CAN BE ASCERTAINED WITH
CERTAINTY, AND PRACTICAL
DIRECTIONS TO MARINERS
FOR THE AVOIDANCE
OF THEIR FURY.

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COMPILED FROM VARIOUS SOURCES

BY
CAPT. JOHN ROSS.

A. ROMAN & COMPANY,

Booksellers, Publishers and Importers,
417 and 119 Montgomery Street, San Francisco.
27 HOWARD ST., NEW YORK.

1869.

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Entered according to Act of Congress, in the year 1869,

By Capt. John Ross,

In the Clerk’s Office of the District Court of the United States
for the Northern District of California.

Printed by SPAULDING & BARTO,
Mining and Scientific Press Job Office,
414 Clay Street, San Francisco.

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ON HURRICANES AND THE
LAW OF STORMS.

In the Northern Hemisphere, when the Polar and Equatorial currents of air are alternating with each other, the regular shifting of the wind round the compass will be through S., S.W., W., N.W., N., N.E., E., S.E., S.—and the changes will take place oftener between south and west, and between north and east, than between west and north, and between east and south.

Similarly in the Southern Hemisphere, it may be inferred that when Polar currents of air alternate with Equatorial, the regular shifting of the wind round the compass will be successive through S., S.E., E., N.E., N., N.W., W., S.W., S.

This is Dove’s “Law of Gyration,” (or the law of the rotation of winds). And collecting the main points into a few general propositions, it may be laid down, that all steady winds are modified by the rotation of the earth, in such a manner that Equatorial currents of air receive a westerly deflection, and Polar currents an easterly deflection; but latitudinal currents suffer no change. The N.E. and S.E. Trade Winds are steady Polar currents. The Monsoons are alternations of a Polar and an Equatorial current, twice during the year. Therefore they are N.E. and S.W. in the Northern Hemisphere, and S.E. and N.W. in the Southern Hemisphere.

The S.W. passage winds of the Northern Hemisphere, and the N.W. passage winds of the Southern Hemisphere, are Equatorial currents.

Bodies of air set in motion from a state of rest, turn the wind-vane in the direction of the meridian as follows:

The Polar current in the Northern Hemisphere from N. to E.

The Polar current in the Southern Hemisphere from S. to E.

The Equatorial current in the Northern Hemisphere from S. to W.

The Equatorial current in the Southern Hemisphere from N. to W.

In general the winds in the Northern Hemisphere are as follows:

Those from N. to E. the Polar currents.

Those from E. to S. the transition of the Polar to the Equatorial.

Those from S. to W. the Equatorial current.

Those from W. to N. the transition of the Equatorial to the Polar.

Also, in the Southern hemisphere, the winds are as follows:

Those from S. to E. the Polar currents.

Those from E. to N. the transition of the Polar to the Equatorial.

Those from N. to W. the Equatorial current.

Those from E. to S. the transition of the Equatorial to the Polar.

Thus, a complete revolution of the wind-vane in the Northern Hemisphere is therefore S.W., N.E., S. with the sun, and in the Southern Hemisphere the rotation is S.E., N.W., S., with the sun, also, in that region.

When the course of a steady wind is obstructed in such a manner as to produce a Hurricane, or Cyclone, the wind has a rotary or whirling motion (as it were, on an axis), while the storm itself has a progressive motion.

N. B.—The rotation of the wind during a hurricane, in the Northern Hemisphere, is in a direction contrary to that in which the hands of a watch move. In the Southern Hemisphere, the rotation is in the same direction as that of the hands of a watch. And hence the following shiftings of the vane: In the Northern Hemisphere, when the vortex (or center) of the storm passes to the westward of the place of observation, the rotation is S.W., N.E., S., with the sun; when the vortex passes to the eastward of the place of observation, the rotation is S.E., N.W., S., against the sun.

In the Southern Hemisphere, if the vortex passes to the westward of the place of observation, the rotation is S.E., N.W., S., with the sun.

If the vortex passes to the eastward of the place of observation, the rotation is S.W., N.E., S., against the sun.