meteors, with different degrees of accuracy and probability. As it would
be superfluous to enter minutely into their various conjectures, which
are frequently grounded on erroneous principles, we shall content
ourselves with selecting a few of the latest remarks; and which are
apparently supported by philosophical reasoning.
Dr. Franklin, in his physical and meteorological observations, supposes
a water-spout and a whirlwind to proceed from the same cause, their only
difference being, that the latter passes over the land, and the former
over the water. This opinion is corroborated by _M. de la Pryme_, in the
_Philosophical Transactions_; where he describes two spouts observed at
different times in Yorkshire, whose appearances in the air were exactly
like those of the spouts at sea; and their effects the same as those of
real whirlwinds.
Whirlwinds have generally a progressive as well as a circular motion; so
had what is called the spout at _Topsham_, described in the
_Transactions_; and this also by its effects appears to have been a real
whirlwind. Water-spouts have also a progressive motion, which is more or
less rapid; being in some violent, and in others barely perceptible.
Whirlwinds generally rise after calms and great heats: the same is
observed of water-spouts, which are therefore most frequent in the warm
latitudes.
The wind blows every way from a large surrounding space to a whirlwind.
Three vessels employed in the whale-fishery, happening to be _becalmed_,
lay in sight of each other, at about a league distance, and in the form
of a triangle. After some time a water-spout appeared near the middle of
the triangle; when a brisk gale arose, and every vessel made sail. It
then appeared to them all by the _trimming_ of their sails, and the
course of each vessel, that the spout was to leeward of every one of
them; and this observation was farther confirmed by the comparing of
accounts, when the different observers afterwards conferred about the
subject. Hence whirlwinds and water-spouts agree in this particular
likewise.
But if the same meteor which appears a water-spout at sea, should, in
its progressive motion, encounter and pass over land, and there produce
all the phenomena and effects of a whirlwind, it would afford a stronger
conviction that a whirlwind and a water-spout are the same thing. An
ingenious correspondent of Dr. Franklin gives one instance of this that
fell within his own observation[57].
A fluid moving from all points horizontally towards a center, must, at
that center, either mount or descend. If a hole be opened in the middle
of the bottom of a tub filled with water, the water will flow from all
sides to the center, and there descend in a whirl. But air flowing on or
near the surface of land or water, from all sides towards a center, must
at that center ascend; because the land or water will hinder its
descent.
If these concentring currents of air be in the upper region, they may
indeed descend in the spout or whirlwind; but then, when the united
current reached the earth or water, it would spread, and probably blow
every way from the center. There may be whirlwinds of both kinds; but
from the effects commonly observed, Dr. Franklin suspects the rising one
to be most frequent: when the upper air descends, it is perhaps in a
greater body extending wider, as in thunder-gusts, and without much
whirling; and when air descends in a spout or whirlwind, he conceives
that it would rather press the roof of a house _inwards_, or force in
the tiles, shingles, or thatch, and force a boat down into the water, or
a piece of timber into the earth, than snatch them upwards, and carry
them away.
The whirlwinds and spouts are not always, though most frequently, in the
day-time. The terrible whirlwind which damaged a great part of _Rome_,
June 11. 1749. happened in the night; and was supposed to have been
previously a water-spout, it being asserted as an undoubted fact, that
it gathered in the neighbouring sea, because it could be traced from
Ostia to Rome.
The whirlwind is said to have appeared as a very black, long, and lofty
cloud, discoverable, notwithstanding the darkness of the night, by its
continually lightening, or emitting flashes on all sides, pushing along
with a surprising swiftness, and within three or four feet of the
ground. Its general effects on houses were, stripping off the roofs,
blowing away chimnies, breaking doors and windows, _forcing up the
floors, and unpaving the rooms_, (some of these effects seem to agree
well with a supposed vacuum in the center of the whirlwind) and the very
rafters of the houses were broke and dispersed, and even hurled against
houses at a considerable distance, &c.
The Doctor, in proceeding to explain his conceptions, begs to be allowed
two or three positions, as a foundation for his hypothesis. 1. That the
lower region of air is often more heated, and so more rarified, than the
upper; and by consequence specifically lighter. The coldness of the
upper region is manifested by the hail, which sometimes falls from it in
warm weather. 2. That heated air may be very moist, and yet the moisture
so equally diffused and rarified as not to be visible till colder air
mixes with it, at which time it condenses and becomes visible. Thus our
breath, although invisible in summer, becomes visible in winter.
These circumstances being granted, he presupposes a tract of land or
sea, of about sixty miles in extent, unsheltered by clouds and
unrefreshed by the wind, during a summer’s day, or perhaps for several
days without intermission, till it becomes violently heated, together
with the lower region of the air in contact with it, so that the latter
becomes specifically lighter than the superincumbent higher region of
the atmosphere, wherein the clouds are usually floated: he supposes also
that the air surrounding this tract has not been so much heated during
those days, and therefore remains heavier. The consequence of this, he
conceives, should be, that the heated lighter air should ascend, and the
heavier descend; and as this rising cannot operate throughout the whole
tract at once, because that would leave too extensive a vacuum, the
rising will begin precisely in that column which happens to be lighted,
or most rarified; and the warm air will flow horizontally from all parts
to this column, where the several currents meeting, and joining to rise,
a whirl is naturally formed, in the same manner as a whirl is formed in
a tub of water, by the descending fluid receding from all sides of the
tub towards the hole in the center.
And as the several currents arrive at this central rising column, with a
considerable degree of horizontal motion, they cannot suddenly change it
to a vertical motion; therefore, as they gradually, in approaching the
whirl, decline from right to curve or circular lines, so, having joined
the whirl, they ascend by a spiral motion; in the same manner as the
water descends spirally through the hole in the tub before mentioned.
Lastly, as the lower air nearest the surface is more rarified by the
heat of the sun, it is more impressed by the current of the surrounding
cold and heavy air which is to assume its place, and consequently its
motion towards the whirl is swiftest, and so the force of the lower part
of the whirl strongest, and the centrifugal force of its particles
greatest. Hence the vacuum which encloses the axis of the whirl should
be greatest near the earth or sea, and diminish gradually as it
approaches the region of the clouds, till it ends in a point.
This circle is of various diameters, sometimes very large.
If the vacuum passes over water, the water may rise in a body or column
therein to the height of about thirty-two feet. This whirl of air may be
as invisible as the air itself, though reaching in reality from the
water to the region of cool air, in which our low summer thunder-clouds
commonly float; but it will soon become visible at its extremities. The
agitation of the water under the whirling of the circle, and the
swelling and rising of the water in the commencement of the vacuum,
renders it visible below. It is perceived above by the warm air being
brought up to the cooler region, where its moisture begins to be
condensed by the cold into thick vapour; and is then first discovered at
the highest part; which being now cooled, condenses what rises behind
it, and this latter acts in the same manner on the succeeding body;
where, by the contact of the vapours, the cold operates faster in a
right line downwards, than the vapours themselves can climb in a spiral
line upwards; they climb, however, and as by continual addition they
grow denser, and by consequence increase their centrifugal force, and
being risen above the concentrating currents that compose the whirl,
they fly off, and form a cloud.
It seems easy to conceive, how, by this successive condensation from
above, the spout appears to drop or descend from the cloud, although the
materials of which it is composed are all the while ascending. The
condensation of the moisture contained in so great a quantity of warm
air as may be supposed to rise in a short time in this prodigiously
rapid whirl, is perhaps sufficient to form a great extent of cloud: and
the friction of the whirling air on the sides of the column may detach
great quantities of its water, disperse them into drops, and carry them
up in the spiral whirl mixed with the air. The heavier drops may indeed
fly off, and fall into a shower about the spout; but much of it will be
broken into vapour, and yet remain visible.
As the whirl weakens, the tube may apparently separate in the middle;
the column of water subsiding, the superior condensed part drawing up to
the cloud. The tube or whirl of air may nevertheless remain entire, the
middle only becoming invisible, as not containing any visible matter.
Dr. Stuart, in the _Philosophical Transactions_, says, “It was
observable of all the spouts he saw, but more perceptible of a large
one, that towards the end it began to appear like a hollow canal, only
black in the borders, but white in the middle; and though it was at
first altogether black and opaque, yet the sea-water could very soon
after be perceived to fly up along the middle of this canal like smoke
in a chimney.”
When Dr. Stuart’s spouts were full charged, that is, when the whirling
pipe of air was filled with quantities of drops and vapour torn off from
the column, the whole was rendered so dark that it could not be seen
through, nor the spiral ascending motion discovered; but when the
quantity ascending lessened, the pipe became more transparent, and the
ascending motion visible. The spiral motion of the vapours, whose lines
intersect each other on the nearest and farthest side of this
transparent part, appeared therefore to Stuart like smoke ascending in a
chimney; for the quantity being still too great in the line of sight
through the sides of the tube, the motion could not be discovered there,
and so they represented the solid sides of the chimney.
Dr. Franklin concludes by supposing a whirlwind or spout to be
stationary, when the concurring winds are equal but if unequal, the
whirl acquires a progressive motion in the direction of the strongest
pressure. When the wind that communicates this progression becomes
stronger above than below, or below than above, the spout will be bent
or inclined. Hence the horizontal process and obliquity of water-spouts
are derived.
WATER-WAY, _gouttiere_, a long piece of timber serving to connect the
sides of a ship to her decks, and form a sort of channel to carry off
the water from the latter by means of scuppers. See that article.
The convexity of the decks, represented by N, M, N, in the
MIDSHIP-FRAME, plate VII. necessarily carries the water towards the
sides, where this piece is fixed, which is principally designed to
prevent the water from lodging in the seams, so as to rot the wood and
oakum contained therein. The water-ways N N are therefore hollowed in
the middle lengthways, so as to form a kind of gutter or channel, one
side of which lies almost horizontally, making part of the deck, whilst
the other rises upwards, and corresponds with the side, of which it
likewise makes a part. They are scored down about an inch and a half, or
two inches, upon the beams, and rest upon lodging-knees or carlings.
They are secured by bolts driven from without through the planks,
timbers, and water-ways, and clinched upon rings on the inside of the
latter.
The scuppers, which are holes by which the water escapes from off the
deck, are accordingly cut through the water-ways.
WAVE, a volume of water elevated by the action of the wind upon its
surface, into a state of fluctuation.
Mr. Boyle has proved, by a variety of experiments, that the utmost force
of the wind never penetrates deeper than six feet into the water; and it
should seem a natural consequence of this, that the water put in motion
by it can only be elevated to the same height of six feet from the level
of the surface in a calm. This six feet of elevation being then added to
the six of excavation, in the part whence that water was raised, should
give twelve feet for the greatest elevation of a wave, when the height
of it is not increased by whirlwinds, or the interruption of rocks or
shoals, which always gives an additional elevation to the natural swell
of the waves.
We are not to suppose, from this calculation, that no wave of the sea
can rise more than six feet above its natural level in open and deep
water; for some immensely higher than these are formed in violent
tempests, in the great seas. These, however, are not to be accounted
waves in their natural state; but they are single waves composed of many
others: for in these wide plains of water, when one wave is raised by
the wind, and would elevate itself up to the exact height of six feet,
and no more, the motion of the water is so great, and the succession of
the waves so quick, that during the time wherein this rises, it receives
into it several other waves, each of which would have been of the same
height with itself. These accordingly run into the first wave, one after
another as it rises: by this means its rise is continued much longer
than it would naturally have been, and it becomes accumulated to an
enormous size. A number of these complicated waves arising together, and
being continued in a long succession by the duration of the storm, make
the waves so dangerous to shipping, which the sailors, in their phrase,
call mountains high.
WAY _of a ship_, the course or progress which she makes on the water
under sail. Thus, when she begins her motion, she is said to be under
way; and when that motion increases, she is said to have fresh way
through the water. Hence also she is said to have _head-way_ or
_stern-way_. See those articles.
WEARING. See the article VEERING.
WEATHER is known to be the particular state of the air with regard to
the degree of the wind, to heat or cold, or to driness and moisture.
WEATHER is also used as an adjective, applied by mariners to every
thing lying to-windward of a particular situation. Thus a ship is said
to have the weather-gage of another, when she is farther to-windward.
Thus also, when, a ship under sail presents either of her sides to the
wind, it is then called the weather-side; and all the rigging and
furniture situated thereon are distinguished by the same epithet; as,
the _weather-shrouds_, the weather-_lifts_, the weather-_braces_, &c.
See the article LEE.
_To_ WEATHER, is to sail to-windward of some ship, bank, or head-land.
WEATHER-BIT, a turn of the cable of a ship about the end of the
_windlass_, without the _knight-heads_. It is used to check the cable,
in order to slacken it gradually out of the ship, in tempestuous
weather, or when the ship rides in a strong current. See also RING-ROPE.
WEATHER-SHORE, a name given by seamen to the shore lying to the
windward.
_To_ WEIGH, denotes in general to heave up the _anchor_ of a ship from
the ground, in order to prepare her for sailing. See also AWEIGH.
WELL, an apartment formed in the middle of a ship’s hold to inclose the
pumps, from the bottom to the lower deck. It is used as a barrier to
preserve those machines from being damaged by the friction or
compression of the materials contained in the hold, and particularly to
prevent the entrance of ballast, &c. by which the tubes would presently
be choaked, and the pumps rendered incapable of service. By means of
this inclosure, the artificers may likewise more readily descend into
the hold, in order to examine the state of the pumps, and repair them,
as occasion requires.
WELL _of a fishing-vessel_, an apartment in the middle of the hold,
which is entirely detached from the rest, being lined with lead on every
side, and having the bottom thereof penetrated with a competent number
of small holes, passing also through the ship’s floor, so that the
salt-water running into the well is always kept as fresh as that in the
sea, and yet prevented from communicating itself to the other parts of
the hold.
WELL-ROOM _of a boat_, the place in the bottom where the water lies,
between the ceiling and the platform of the stern-sheets, from whence it
is thrown out into the sea with a scoop.
WHARF, a perpendicular building of wood or stone raised on the shore of
a road or harbour, for the convenience of lading or discharging a vessel
by means of cranes, _tackles_, _capsterns_, &c.
A wharf is built stronger or slighter, in proportion to the effort of
the tide or sea which it is to resist, and to the weight which it is
intended to support.
WHARFINGER, the person who has the charge of a wharf, and takes account
of all the articles landed thereon, or removed from it, into any vessel
lying alongside thereof; for which he receives a certain fee called
wharfage, which becomes due to the proprietor for the use of his
machines and furniture.
WHEEL _of the helm_. See HELM.
WHELPS. See the article CAPSTERN.
WHIP, a sort of small tackle, either formed by the communication of a
rope with a single immoveable block, as fig. 3. plate XI. or with two
blocks, one of which is fixed, and the other moveable, as fig. 5. It is
generally used to hoist up light bodies, as empty casks, &c. out of a
ship’s hold, which is accordingly called _whipping_ them up. See TACKLE.
_To_ WHIP, is also to tie a piece of packthread, spun-yarn, &c. about
the end of a rope, to prevent it from being untwisted and loosened.
_Boatswain’s_ WHISTLE. See CALL.
WHOODING. See the article RABBIT.
WINCH, a cylindrical piece of timber, furnished with an axis, whose
extremities rest in two channels placed horizontally or perpendicularly.
It is turned about by means of an handle resembling that of a draw-well,
grind-stone, &c. and is generally employed as a _purchase_, by which a
rope may be more conveniently or more powerfully applied to any object,
than when used singly, or without the assistance of mechanical powers.
WIND, _vent_, a stream or current of air which may be felt; and usually
blows from one part of the horizon to its opposite part.
The horizon, besides being divided into 360 degrees, like all other
circles, is by mariners supposed to be divided into four quadrants,
called the north-east, north-west, south-east, and south-west quarters.
Each of these quarters they divided into eight equal parts, called
points, and each point into four equal parts, called quarter-points. So
that the horizon is divided into 32 points, which are called _rhumbs_ or
_winds_; to each wind is assigned a name, which shews from what point of
the horizon the wind blows. The points of north, south, east, and west,
are called _cardinal points_ and are at the distance of 90 degrees, or
eight points from one another.
Winds are either constant or variable, general or particular. Constant
winds are such as blow the same way, at least for one or more days; and
variable winds are such as frequently shift within a day. A general or
_reigning_ wind is that which blows the same way, over a large tract of
the earth, almost the whole year. A particular wind is what blows, in
any place, sometimes one way, and sometimes another, indifferently. If
the wind blows gently, it is called a breeze; if it blows harder, it is
called a gale, or a stiff gale; and if it blows with violence, it is
called a storm or hard gale[58].
The following observations on the wind have been made by skilful seamen:
and particularly the great Dr. Halley.
1st. Between the limits of 60 degrees, namely, from 30° of north
latitude to 30° of south latitude, there is a constant east wind
throughout the year, blowing on the Atlantic and Pacific oceans; and
this is called the _trade-wind_.
For as the sun, in moving from east to west, heats the air more
immediately under him, and thereby expands it; the air to the eastward
is constantly rushing towards the west to restore the equilibrium, or
natural state of the atmosphere; and this occasions a perpetual east
wind in those limits.
2d. The trade-winds near their northern limits blow between the north
and east, and near the southern limits they blow between the south and
east.
For as the air is expanded by the heat of the sun near the equator;
therefore the air from the northward and southward will both tend
towards the equator to restore the equilibrium. Now these motions from
the north and south, joined with the foregoing easterly motion, will
produce the motions observed near the said limits between the north and
east, and between the south and west.
3d. These general motions of the wind are disturbed on the continents,
and near their coasts.
For the nature of the soil may either cause the air to be heated or
cooled; and hence will arise motions that may be contrary to the
foregoing general one.
4th. In some parts of the Indian ocean there are periodical winds, which
are called Monsoons; that is, such as blow half the year one way, and
the other half-year the contrary way.
For air that is cool and dense, will force the warm and rarefied air in
a continual stream upwards, where it must spread itself to preserve the
equilibrium: so that the upper course or current of the air shall be
contrary to the under current; for the upper air must move from those
parts where the greatest heat is; and so, by a kind of circulation, the
N. E. trade-wind below will be attended with a S. W. above; and a S. E.
below with a N. W. above: And this is confirmed by the experience of
seamen, who, as soon as they get out of the trade-winds, generally find
a wind blowing from the opposite quarter.
5th. In the Atlantic ocean, near the coasts of Africa, at about 100
leagues from shore between the latitudes of 28° and 10° north, seamen
constantly meet with a fresh gale of wind blowing from the N. E.
6th. Those bound to the Caribbee islands, across the Atlantic ocean,
find, as they approach the American side, that the said N. E. wind
becomes easterly; or seldom blows more than a point from the east,
either to the northward or southward.
These trade-winds, on the American side, are extended to 30, 31, or even
to 32° of N. latitude; which is about 4° farther than what they extend
to on the African side: Also, to the southward of the equator, the
trade-winds extend three or four degrees farther towards the coast of
Brasil on the American side, than they do near the Cape of Good Hope on
the African side.
7th. Between the latitudes of 4° and 4° south, the wind always blows
between south and east. On the African side the winds are nearest the
south; and on the American side nearest the east. In these seas Dr.
Halley observed, that when the wind was eastward, the weather was
gloomy, dark, and rainy, with hard gales of wind; but when the wind
veered to the southward, the weather generally became serene, with
gentle breezes next to a calm.
These winds are somewhat changed by the seasons of the year; for when
the sun is far northward, the Brasil S. E. wind gets to the south, and
the N. E. wind to the east; and when the sun is far south, the S. E.
wind gets to the east, and the N. E. winds on this side of the equator
veer more to the north.