For a right understanding of anything
that has been done, or can be done for the
prevention of wrecks off our shore, it is
necessary to have, in the first instance, some
clear notion of the nature of the waves
which we desire to keep in check.

Waves are caused by the rubbing of the
wind over a sheet of water, forcing it into
undulations, which are most considerable
when the wind is roughest, and has freest
play over a moveable and level surface of the
widest expanse. Thus there is one cause for
the ripple of the pond and the Atlantic
billow. When there is an off-shore gale, the
waves near land are low, and they mount
higher and higher as we travel seaward over
them. The wind from the coast, when first
striking the water, raises a wave of a certain
height, and when the wind can no longer
force up its increasing weight against the
increasing tendency, by reason of its weight
to tumble down again, it falls; and by its
fall gives undulating movement to the sea
beyond it, as a beam would if it fell on the
same spot. The wind, helped by the
tendency to rise in undulation thus established,
lifts the next wave higher, it is heavier
before it falls; and when it falls a stronger
undulation is produced by the increased
weight of its mass. The force of the wind,
therefore, will be able to carry up the next
wave higher still; and while the weight of
the waves is thus growing, and the undulation
produced by their fall is deepened, the
wind, clear of obstruction from hills, trees,
and other fixed impediments, can gather all
its force into each blow, and becomes
mightier to raise the waters towards heaven.
So we come to the huge undulations of the
mid- Atlantic.

Because the risings and the fallings
necessarily must follow each other in succession,
the descent of one wave urging up the next,
the whole surface of the sea seems to be
moving forwards; but there is no such real
progress in the water. When over the
surface of a field of corn, the waves run with
the wind, every blade bends, rises, and
returns to its place. Undulations may run
rapidly along a shaken rope, yet the rope
does not move forward with them. When
a swell passes a ship at anchor in a calm
day, if a piece of wood be dropped over
the side, though the waves may be running
towards shore at the rate of fifteen miles
an hour, the wood rises and falls where it
was dropped, and does not travel with
them. Sometimes at sea an undulation
which remains for a time after its cause
has departed, crosses another of which the
cause is then in operation. If these waves
were propelling forces, they would dash each
other into foam, with a wild conflict. Being
mere undulations of the water, they cross
over each other without disturbance. It is
true that a vessel with her bows pointed
in the direction towards which the waves are
travelling, although uninfluenced by tide,
will slowly forge a-head; but this she does
simply because the weight of her mass
propels her forward down the slope of each
undulation by which she is lifted. It might
have seemed unnecessary to dwell on an
account of the formation of ordinary deep
water waves (which must not be confounded
with the tidal wave that underlies them),
if a misapprehension as to their nature—
which no man of eminence since Newton's
day has felt a doubt about—had not caused
many conflicting opinions to be expressed
before the Harbour of Refuge Commission,
fourteen years ago.

As to the height attained by billows in
mid ocean, reports do not agree. To the eye
of the seafarer, it truly seems that they
mount up to heaven, they go down again to
the depths; but, of the height of waves in
the sea, as of the number of stars in the sky,
we form our impression subject to some
causes of optical illusion. The rapid movement
of the vessels from which observations
of the height of waves have to be taken,
makes it difficult to include every allowance
due to error in a measurement. The best
attempts can only yield approaches to the truth.
The late Doctor Scoresby, during several
hard gales in the Atlantic, measured many
waves of about thirty feet, and one of forty-
three. Another observer measured forty-five
feet waves off the Island of Ascension, and
declared that they sometimes rose sixty or
seventy feet in the adjacent open sea. A
third, and very competent observer, testified
before the Select Committee on Shipwrecks,
fifteen years ago, that he had measured the
height of waves in the Atlantic in a heavy
gale, and found none to exceed nineteen feet,
after repeated trials, and when every
conceivable allowance had been made for error.
And these calculations refer to the massive
billows far away in the wide and deep
Atlantic. In the narrow and comparatively
shallow seas that surround England,
undulation cannot be established on so grand a
scale. Mr. Thomas Stevenson, a famous
builder and designer of light-houses and
artificial harbours, says, that at the mouth of a
harbour in the German Ocean with six
hundred miles breadth of sea before it, during
south-easterly gales, the extreme height of a
wave was thirteen feet and a-half. In the
deep water of the German Ocean, when a
north-easter is blowing, he has no doubt that
they rise considerably higher. The Count
de Marsilli found the highest wave on the
coast of Languedoc, with six hundred miles
of sea before it, to be fourteen feet ten inches.
On the eastern coast of England there is a
sea-front of about three hundred miles, and
we may assume fifteen feet to be the utmost
height to which the waves are raised in any
gale. When the force that raised the
undulation is withdrawn, the effect continues and
subsides by degrees under the ordinary