Wave break

“ No matter how fiercely the waves are running, let the wind lull, and a brisk rain of an hour will take all the rough edge off them. It is the dashing and breaking waves that sailors dread. A regular swelling wave, no matter how high it towers, will do no harm, as a vessel will rise with it, and ride lightly over. ”

“ I saw the worst assault at night on a seaside parade where the sea smote on the doors of England with the hammers of earthquake, and a white smoke went up into the black heavens. There one could thoroughly realise what an awful thing a wave really is. I talk like other people about the rushing swiftness of a wave. But the horrible thing about a wave is its hideous slowness. ”

“ If the liquid space is free, the vibrations are gradually extinguished; if they meet an obstacle, there is a shock. If the obstacle is a shore, they form a tidal-wave and raise large billows, while a few miles away from the shore the sea is quiet. When the obstacle is a shoal or a contrary vibration, heavy waves are raised on the surface of the sea; they seem to start from the bottom, and put ships in great danger. The waves produced in both cases are waves of transmission, as also are those which beat on reefs in pleasant weather, and those which prolong the swell after storms. ”

“ A study of breaking waves shows us that the cause of their great power to effect damage to coast structures, such as piers, harbour works, and shipping in harbours, is really due to the forward motion of the water as the wave is breaking. Every cubic foot of water weighs 631⁄2 lbs., so that a cubic yard of water weighs about three-quarters of a ton. If this water is moving with a speed of many feet per second in a forward direction, the energy of motion stored up in it is tremendous, and fully sufficient to account for the destructive power of storm waves on a coast. ”

“ Up came a second wave. The lulling of the wind gave the waves a chance to gather force and height. This one curled fairly over my head and, looking up and over my shoulder at the great, green, foam-streaked wall of water, I thought my last minute above the surface had come!
It broke. I can remember nothing at all of the ensuing few moments. I only know that I was smothered, drowned, completely overwhelmed by the deluge of water that came inboard. The force of it burst open the slide of the hatch and barrels of water flooded into the cabin. The Wavecrest settled. ”

“ If you are far enough out, the breaking wave curves over you like a roof inlaid and prismatic, bending down on the other side of you in layers of chalk and drifts of snow, and the lightning flash of the foam ends in the thunder of the falling wave. ”

“ When the water begins to increase, it comes on with a prodigious noise as if it were an earthquake. In its first great approach it makes three great waves. The first wave washes over the bark from stem to stem: The second is not so strong; at the third they raise the anchor and resume their voyage up the river, rowing with such swiftness that they seem to fly for the space of six hours, while the flood lasts. ”

“ IT is impossible for the most careless spectator to look at a steam-vessel making her way along a lake, a boy’s boat skimming across a pond, or even a duck paddling on a stream, without noticing that the moving body is accompanied in all cases by a trail of waves or ripples, which diverge from it and extend behind. In the case of a steamer there is an additional irregular wave-motion of the water caused by the paddle-wheels or screw, which churn it up, and leave a line of rough water in the steamer’s wake. ”

“ It has already been shown that when a single wave-disturbance is made upon water it gradually develops itself into a group of waves. The single wave when created causes a disturbance on water which extends both forwards and backwards. As the wave moves forward the wave-disturbance is always growing in front and dying away behind, and the wave-group therefore moves forward, but the centre or limits of the group move with only half the velocity of a single wave. ”

“ The motion of the particles of the water in a deep-sea wave resembles that of the white knobs in the model described. Those who swim will recall to mind their sensations as a sea wave surges over them. The wave [6] lifts up the swimmer, then pushes him a little forward, then lets him down, and, lastly, drags him back. It is this dragging-back action which is so dangerous to persons who cannot swim, when they are bathing on a steep coast where strong waves are rolling in towards the shore. ”

“ As soon as the shock is over, the body of water thus forced out to sea returns as a huge wave, and, on approaching a sloping shore, rears up like a wall, and breaks with overwhelming force. Sometimes, however, its volume, height, and velocity are so great that it comes ashore bodily, and breaks far inland, causing even greater destruction to life and property. ”

“ Now this [139] motion increases with the onward career of the gale. “Vires acquirit eundo.” And when the mass of the fluid over which the wind is blowing has once been agitated, and the equilibrium of its upper layers been thoroughly disturbed, if the current of air not only continue, but wax stronger and stronger, there scarcely seems any limit to the momentum which the rolling wave may thus acquire. The arithmetic of a few facts upon this subject will, however, give us some idea of what that momentum must be on certain occasions. ”

“ A breaking wave concentrates its transmitted force on a portion of the water forming the undulation, which, consequently, strikes a more powerful blow over a limited area against any structure than the more distributed shock of a simple undulation beating against a vertical wall. Moreover, the recoil of broken waves down a sloping beach or rubble mound produces a greater scour than the simple reflection of an undulation from a vertical wall, especially where the depth is sufficient to provide a cushion of water below the undulation, protecting the toe of the wall from the wash of recoil. ”

“ As each wave slows, the next wave behind it, in deeper water, tends to catch up. As the wavelength decreases, the height generally becomes greater. The lower part of a wave, being nearest the bottom, is slowed more than the top. This may cause the wave to become unstable, the faster-moving top falling forward or breaking. Such a wave is called a breaker, and a series of breakers is surf. Swell passing over a shoal but not breaking undergoes a decrease in wavelength and speed, and an increase in height, which may be sudden and dramatic, depending on the steepness of the seafloor’s slope. ”

“ Each drop as it strikes the water becomes a centre of disturbance, from which a series of ring-ripples expand outwards. Gravity and inertia are the agents by which this wave-motion is produced, and a rough experiment will suffice to show that the rate of propagation does not amount to a foot a second. A series of slight mechanical shocks is experienced by a body plunged in the water, as the wavelets reach it in succession. But a finer motion is at the same time set up and propagated. ”

“ The wave which is breaking into foam, which is rippling over the pebbles, which throws up the broken water, which falls back on to the land and makes music, sound, melody as it breaks—that is the wave which is nearly over; it is the wave whose course is run. ”

“ You climb wave after high wave, and are not swallowed up as you expected. You wait, between guns, for the boom and the shock of the next, with a passionate anticipation, as you wait for the next wave. ”

“ By some unexplored tidal law, parties would seem to move through successive ebb and flow toward a final culmination of mischievous extreme, each refluent wave returning with heavier mass, until the accumulated weight of madness and folly overtopples, breaks, and dissolves in noisy foam. ”

“ Without tempest, with only rollers to deal with, and with a moderate wind right abaft, a cross wave will give your craft such a shock, that the ship's bell will strike, and if these big rollers with their sweeping motion, continue for any time, your masts will go by the board, your seams will open—you will be a wreck. ”

“ From the beach, a little below the foot of the tower, seaward, as far as the eye could reach through the mist and spray, the ocean tossed and rolled. Great hills of water, green and angry, rose as though pushed up from below, their crests lashed into foam and then blown into vapor by the gale; wave succeeded wave, until a mighty host of waters, rank on rank, impelled by the wind, dashed themselves to foam on the ever-resisting shore. ”

“ By the initial impulse of explosion or lifting of the ground, a ‘great sea wave’ is generated, which travels 175shorewards with a velocity dependent upon its size and the depth of the ocean. At the same instant, a ‘sound wave’ may be produced in the air, which travels at a quicker rate than the ‘great sea wave.’ A third wave which is produced, is an ‘earth wave,’ which will reach the shore with a velocity dependent on the intensity of the impulse and the elasticity of the rocks through which it is propagated. ”

“ The creation of the waves will bring it to rest in time, unless it is continually urged forward by some external and impressed force, and wave-generation is a reason for a part at least of the resistance we experience when we attempt to push it along. ”

“ But when the bottom of the wave strikes the land, it stops, while the top goes on. It no longer has the bottom of the wave to hold it up. Where was solid water beneath it, is now air, and for the first time it feels the grip of gravity, and down it falls, at the same time being torn asunder from the lagging bottom of the wave and flung forward. And it is because of this that riding a surf-board is something more than a mere placid sliding down a hill. In truth, one is caught up and hurled shoreward as by some Titan’s hand. ”

“ These invasions of the sea, or tidal-waves, are often more dreaded by the people, who have had experience of them, than the shocks on land. The huge wave* are also propagated in the ocean to a very great distance from the center of disturbance. ”

“ We know how, as the circles widen, the height of the wave grows less and less, until, at no great distance from the centre of disturbance, the wave can no longer be discerned, so slight is the slope of its advancing and following faces. How tremendous, then, must have been the upheaval of the bed of ocean by which wave-circles were sent across the Pacific, retaining, after travelling 5000 miles from the centre of disturbance, the height of a two-storied house! ”

“ For, see, since a wave is only a communicated agitation or impetus, and since the water that composes a wave is changing every instant, new water is rising into the wave as fast as the wave travels. You slide down this new water, and yet remain in your old position on the wave, sliding down the still newer water that is rising and forming the wave. You slide precisely as fast as the wave travels. If it travels fifteen miles an hour, you slide fifteen miles an hour. Between you and shore stretches a quarter of mile of water. ”

“ In all departments of natural science we find ourselves confronted by the phenomena of wave-motion. In the study of earthquakes and tides, telegraphs and telephones, as well as terrestrial temperature, no less than in the examination of water waves and ripples, sound, music, or light and heat, we are bound to consider waves of some particular kind. ”

“ In addition to seismic sea waves, earthquakes below the surface of the sea may produce a longitudinal pressure wave that travels upward at the speed of sound. When a ship encounters such a wave, it is felt as a sudden shock which may be so severe that the crew thinks the vessel has struck bottom. ”

“ As a wave progresses over the surface, wave-energy is continually being imparted to portions of the water in front, and it is transferred away from others in the rear. In the very act of setting a fresh particle of water in oscillation, the portions already vibrating must diminish their own motion. They may hand on the whole of their energy or only a part of it to their neighbours. This distinction is a very important one, and it determines whether a single act of disturbance shall create a solitary wave or wave-train in a medium. ”

“ Storms are a sort of violent readjustment in some polarized flow. You have a polarized circuit, a circuit of unstable equilibrium. The instability increases till there is a crash. Everything seems to break down. Thunder roars, lightning flashes. The master roars, the whip whizzes. The sky sends down sweet rain. The ship knows a new strange stillness, a readjustment, a refinding of equilibrium. ”

“ It must however be understood that it is not the particles of water first set in motion that travel and spread out in concentric circles; but the force is propagated by the rising and falling of each separate particle of water as it is disturbed by the momentum of the descending wave before it. When standing at a pier-head, or on a rock against which the sea dashes, it is usual to hear the observer cry out, if the weather is stormy and the waves very high, "Oh! ”

“ The whole theory of the trail of waves made by a canal-boat is only comprehensible if it is clearly seen that a water-surface wave has a certain velocity determined by its wave-length. If the wave-speed is small, the waves are short. As the speed increases the waves get longer. Or the matter may be put in another way. We may say that just as a pendulum has a certain rate of vibration depending on its length, so a water wave has a certain frequency, and therefore, a certain speed of propagation dependent upon the wave-length, or shortest distance from one wave-crest to the next. ”