(Abstract of a paper read before the National Geographic Society, Nov.
15, 1889.)
In preparing an abstract of this paper it is of course difficult to
adhere very closely to the original, inasmuch as that was illustrated
by forty-five lantern slides, while it is only practicable to present a
few plates with this abstract. I may therefore be permitted to give
only a general outline of the subject, with perhaps a more detailed
discussion of one or two of the most notable recent hurricanes off our
Atlantic coast.
The term "Law of Storms" is applied to the code of rules that should
govern the action of the master of a vessel when he has reason to
suspect the approach of a dangerous storm. It will be seen that this
definition, like the code itself, is somewhat vague. So many
considerations enter as factors in the question that it is wholly
impossible to lay down any rules that shall be applicable alike to a
high-powered, well-manned steamship, and to a heavily-laden,
poorly-equipped and short-handed sailing vessel. Disregarding such
differences of conditions (which are, of course, of vital importance in
each individual case, but which cannot be discussed in a brief general
essay), the two grand divisions of the subject may be compared to
_grand strategy_ and _field tactics_. By this I mean that a broad,
comprehensive view of the whole subject of ocean storms--their regions,
seasons, size, severity, and tracks--is one very important part of the
navigator's duty in planning a long campaign, or voyage; and, secondly,
the handling of his vessel when actually in the fight--the coolness,
clear-headedness, and trained experience that utilizes every resource
of the best seamanship and navigation in a fearful struggle with the
fury of a hurricane--all of these are also an essential part of the
education of the ideal sea-captain.
Thanks to the progress of meteorologic research it is comparatively
easy nowadays for anyone to get a very good general idea of the great
hurricane regions of the globe, and the seasons when these dreaded
tropic cyclones prevail in each of these regions. The evidence on this
subject is cumulative and practically conclusive, so that it is
universally known and recognized that the hurricane months are the
summer months in each hemisphere; hurricanes originate in the tropics,
move westward, then poleward into the temperate zones, and finally
eastward in higher latitudes, receding gradually from the equator;
moreover, the essential difference between hurricanes north and south
of the line is as follows: In the Northern Hemisphere the rotation of
the cyclonic whirl is _against_ the hands of a watch, and in the
Southern, _with_. The noted hurricane regions are the West Indies,
coast of China and Japan, Bay of Bengal (especially in May and October,
at the time of the change of the monsoons), and the South Indian Ocean
(about Mauritius). Less noted regions are the South Pacific (East of
Australia), the North Pacific (west of the Mexican coast), and the
Arabian Sea. In planning a distant voyage a navigator should therefore
consider the hurricane regions through which he must pass, just as he
considers the prevailing winds--the trades, monsoons, and ocean
currents.
The handling of a ship in a hurricane is a very different sort of a
thing from this general survey of the entire field, and, without the
eminently practical qualities that we all associate with a good officer
of the navy or mercantile marine, no mere theoretic knowledge can avail
much. And yet this is one of those cases where practice and theory
should go hand in hand,--not theory as something vague and unreal, but
theory as based upon a firm foundation of observed facts. If a vessel
encounter a hurricane, certain conclusions can be drawn from
observations of the shifts of wind, the fluctuations of the barometer,
the appearance of the clouds, and the direction of the ocean swell; the
master of that vessel will undoubtedly draw such conclusions, and store
them away in his mind as part of his fund of experience upon which to
base action at some future time. But if he can consider his own
observations, while fresh in mind, in connection with the observations
made on board many other vessels that encountered the same storm, and
modify or verify his conclusions by such comparison, there cannot be a
doubt but that the lesson will be of far greater value. Sailors lead a
rough life, and their training is often acquired by experience alone.
Moreover, there are certain things that tend to discourage effort on
the part of junior officers, even on board naval vessels: they realize
that their duty is not to originate orders but to execute them, and
sooner or later they get out of the habit of reflecting upon the action
taken to avoid a storm or manoeuver in one, not knowing at the time
what considerations lead to the action that was taken, and not always
having anything brought forcibly to their attention to indicate with
certainty whether the action was well-considered or ill-advised. Upon
finally attaining command themselves they are not, therefore, as well
posted as they might otherwise have been. I mention these things to
explain the undoubted fact that comparatively few masters of vessels
are well posted in certain very important additions to the old law of
storms, as it was discovered by Redfield and enforced by Reid,
Piddington, Thom, and other early writers. In fact, of all the
navigators of various nationalities who have charge to-day of the
commerce of the world, probably four-fifths are wholly ignorant of the
progress that has been made in this direction in the past fifty years.
That such is the case is not, in my opinion, wholly their fault: it is
owing to the fact that far too little attention has been paid to clear,
forcible, and convincing explanation; it is the fault of the teachers,
no less than the scholars,--of meteorologists who talk over the heads
of their audiences, instead of stating facts and conclusions in a way
to command attention and respect from the practical men who furnish the
data, and who deserve some tangible results in return for their long
years of voluntary observation.
[Illustration: A ship in the heart of a cyclone. From Reid's "Law of
Storms."]
It is difficult to put this matter very clearly to those who are not
familiar with the conditions that govern the management of a vessel at
sea, and I shall only attempt to do so in a very general way. It should
be understood, first of all, that a hurricane is an enormous whirlwind,
so large, in fact, that its circular nature was generally recognized
only about fifty years ago. At the immediate center of the whirl there
is a calm space, from five or ten to thirty or forty miles in diameter,
generally with blue sky and bright sunlight. Within a short distance of
this central calm the wind blows with frightful violence, and here a
vessel is driven along in absolute helplessness, enveloped in midnight
darkness, buried in a flying mass of foam and spray, with every sound
annihilated by the roar and shrieks of the elements. The core of the
hurricane, as this region has been called, is small, relative to the
entire area, and it thus happens that a few miles may make all the
difference between shipwreck and safety. The question is, then, to
avoid getting into the core, or heart, of the hurricane. It is evident
enough that if the wind blow in a strictly circular direction around
the center, the bearing or direction of the center must be at exactly
right angles (eight points) to the right (or left) of the direction of
the wind. In other words, in the Northern Hemisphere (where the
direction of rotation is against the hands of a watch) the center bears
eight points to the right of the wind (that is, to the right of the
direction from which the wind blows); in the case of a hurricane off
our coast, for instance, if the wind be NE. at Hatteras the center
would bear (according to the 8-point rule) SE. Considering, further,
that the entire whirl has a progressive motion along a path, or track,
if an observer at Hatteras find that the NE. wind freshens rapidly,
without any shift or change of direction, it is equally evident that
the center of the storm is approaching directly toward that point. In a
similar situation at sea, a shipmaster would naturally see that his
vessel was in a position of great danger: evidently the best thing to
do would be to run before the wind, thus getting out of the way of the
approaching hurricane. This simple case will explain pretty clearly, I
think, how rules were at once formulated and adopted, as soon as
Redfield had proved the approximately circular character of these
storms.
Without going further into this subject, inasmuch as this 8-point rule
is perhaps the most important of all the rules--indeed, all of them
follow directly from it,--suppose that subsequent research, based upon
careful observation and the accurate charting of hundreds of reports
from vessels in similar storms in various oceans, proved conclusively
that the wind in a hurricane does not blow in strictly circular whirls,
but rather spirally inward, so that with a NE. wind off Hatteras the
center bears probably S SE., or even South: evidently this is a matter
of vital importance to the navigator, and all the old rules should be
remodeled to suit the discovery. Such is, indeed, actually the fact,
and in most cases nothing could be worse than to run directly before
the wind; in any event it would be dangerous, and in the case of a
slow-moving cyclone it might readily lead the vessel directly into the
core of the hurricane. This is known to have been the case in many
instances, and vessels have thus been drawn into the inner whirls of
hurricanes and kept there for several days, making one or more complete
revolutions around the center before they could extricate themselves.
In fact, they might never have gotten out, if the storm itself had not
moved off and left them.
The first of the accompanying plates, entitled,