Wavefront

“ The rhythm of waves beats in the sea like a (48) pulse in living flesh. It is pure force, forever embodying itself in a succession of watery shapes which vanish on its passing.
I stand on my dune top watching a great wave coursing in from sea, and know that I am watching an illusion, that the distant water has not left its place in ocean to advance upon me, but only a force shaped in water, a bodiless pulse beat, a vibration.
Consider the marvel of what we see. Somewhere in ocean, perhaps a thousand miles and more from this beach, the pulse beat of earth liberates a vibration, an ocean wave. ”

“ 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. ”

“ WE have all stood many times by the seashore, watching the waves, crested with white foam, roll in and break upon the rocks or beach. Every one has more than once cast a stone upon still water in a lake or pond, and noticed the expanding rings of ripples; and some have voyaged over stormy seas, whereon great ships are tossed by mighty billows with no more seeming effort than the rocking of a cradle. In all these things we have been spectators of a wave-motion, as it is called, taking place upon a water surface. ”

“ It is that all space is filled with what we may call an ocean of æther, which can be tossed into waves and ripples just as the air we breathe is traversed in all directions by aerial vibrations, and the restless sea by waves and ripples on the water-surface. ”

“ Their chief object has been to show you that the swiftly moving ocean waves, which dash and roll unceasingly against the coast-lines of our island home, are only instances of one form of wave-motion, of which we find other varieties in other media, giving rise to all the entrancing effects of sound and light. In these expositions we have been able to do no more than touch the fringe of a great subject. ”

“ Our new waves are very short; an army of ten thousand, marching in single file, would find room in an inch; but, though small, they are swift in motion: they will travel seven times around the earth in a second, and then be prepared for an interstellar journey. When they impinge on us, compensating for small size by vast number, they still produce a powerful sensation—we call it heat. Their effect upon the ear or eye is about the same as upon any other portion of the body; our ears are deaf, our eyes blind to them. ”

“ A careful observer can in this school of Nature instruct himself in all the laws of wave-motion, and gather a fund of knowledge on this subject during an hour’s dalliance at low tide on some sandy coast, or in the quiet study of seaside pools, the surface of which is corrugated with trains of ripples by the breeze. ”

“ Every breaking wave had its summit illuminated by a light similar to that of phosphorus, and the sides of the vessel, coming in contact with the sea, were strongly marked by a luminous line. Great bodies of light moved in the water along our side, sometimes slower, sometimes quicker ”

“ The waves produced are like the billows of the ocean, and have the same quality of loud booming tones, possessing the same wild exuberance of motion. The passionate torrent swirls in wild ecstasy around the rocks, springing aloft and tipping the waves with a silvery radiance or clashing its emerald waters in plumes of spray. One never tires gazing at the waters leaping and gliding like living creatures as they dash themselves to pieces on the rocks, or listening to the swash and gurgle of the rapid waters or the keen clash of heavier waves. ”

“ The waves of the sea even appear to the eye to be endowed with a progressive motion, but an instant's observation will convince us of our error; for if such were the case, every object floating on the ocean would be gradually carried on shore. A vessel floating on the waves is not carried along by them, at least not until it reaches within a few yards of the shore, where the water is really in motion; but out in the open sea a floating body will alternately rise on their crests, and fall into the valleys that separate them. ”

“ Observe a sea-fowl, or, if you are a swimmer, abandon yourself to the action of the waves; you are not carried forward, but simply rocked up and down. The propagation of a wave is the propagation of a form, and not the transference of the substance which constitutes the wave.
The length of the wave is the distance from crest to crest, while the distance through which the individual particles oscillate is called the amplitude of the oscillation. You will notice that in this description the particles of water are made to vibrate across the line of propagation. ”

“ 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! ”

“ On the earth, houses, towns, cottages, and country feel every shock given to the exterior of the globe. On sea, the vessels rocked by the waves are still in motion; in the air, the balloon oscillates incessantly on the fluid strata of divers densities. ”

“ The waves which spread round a central point when a stone is thrown into the water, give one the idea that the water which forms the wave really moves towards the observer. But it is not so, as may be readily proved by placing on the surface a floating body, which we shall find is but little, if at all, influenced by the undulations of the water. The appearance of rolling waves given on the stage by means of a painted cloth, to which an undulatory motion is given, is an instance of this apparent movement. ”

“ 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. ”

“ What a significant symbol is afforded by the wave! There is much in life, in history, and in all nature that is typified by it. We have cold waves and hot waves, and in the spring and fall migrations of the birds we have “bird waves.” Earthquake shocks go in waves and circles; how often our views and conceptions of things are expressed by the circle! It is a symbol of most profound meaning. It helps us to understand how the universe is finally inexplicable; that there is neither beginning nor end, and that it retreats forever into itself. ”

“ We see a wave a quarter of a mile off, then a few hundred yards nearer in, then just offshore; we seem to have been watching the same travelling mass of water—there has been no appreciable change in mass or in shape—yet all the while the original beat has taken on a flowing series of liquid bodies, bodies so alike, so much the same, that our eye will individualize them and follow them in—the third wave, we say, or the second wave behind the great wave. ”

“ Among the waves which reach the eye many, nay, most, are so small that ordinary vision cannot perceive their action. Take, however, a telescope, and so gather them together as to intensify this action, and they are rendered perceptible, just as the unnoticed heaving of ocean becomes a manifest wave-motion when it reaches a regularly narrowing inlet. Thus, from stars so remote that their light has required thousands, or, even in some cases, perhaps, hundreds of thousands of years in reaching us, the light-waves flow steadily in upon us. ”

“ LEAVING the consideration of waves and ripples on a water-surface, we pass on to discuss the subject of waves and ripples in the air. Nearly every one is aware, in a general way, that sound is due to a disturbance created in the atmosphere. Few, however, are fully acquainted with the nature of the movements in the air which excite our sense of hearing, and to which we owe, not only the pleasures of conversation and the enjoyment of all the sounds in nature, but those delights of music which are amongst the purest forms of pleasure we possess. ”

“ The crest of a wave falls over a portion of air, imprisoning it for a moment, and the mingled air and water of different densities prevent the light of the sun or sky from going straight down into the black depths and being lost, but by being reflected and turned back it shows like beautiful white lace, constantly created and dissolved with a thousandfold more beauty than any that ever came from human hands. ”

“ 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. ”

“ I felt the same tingling force flooding through me that I had already once experienced, as our flying ship raced on, again swaying and spinning as it flashed through the mighty ether-currents whose meeting and collision formed the great region of vibrations about us, though outside was only the same blackness as before. With every moment, though, our ship, our mechanisms, our own bodies, were glowing with waxing light, while in the darkness behind I saw that the great swarm of ships racing after us was itself aglow now with light, as it, too, rushed into the great radio-active region after us. ”

“ 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. ”

“ Each kind of medium may allow of waves peculiar in their conditions, so that it is a beautiful exercise in analogical reasoning to decide how, in making inferences from one kind of medium to another, we must make allowance for difference of circumstances. The waves of the ocean are large and visible, and there are the yet greater tidal waves which extend around the globe. From such palpable cases of rhythmical movement we pass to waves of sound, varying in length from about 32 feet to a small fraction of an inch. ”

“ He is inevitably marked, to ear and eye, as the legendary ninth wave, the foamiest green breaker of the line, ever re-forming and breaking, so long as he is visible, brighter, taller, and farther in-shore than the rest. ”

“ 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. ”

“ If we could see the particles of the air in the concert-room, and fasten our attention upon any one of them, we should see it executing a most complicated motion under the combined action of these air-wave-producing instruments. We should be fascinated by the amazing dance of molecules to and fro and from side to side, as the medley of waves of compression or rarefaction embraced them and drove them hither and thither in their resistless grasp. ”

“ And further, if there chance to blow any wind, or that the air between you and the Object be in a motion or current, whereby the parts of it, both rarify'd and condens'd, are swiftly remov'd towards the right or left, if then you observe the Horizontal ridge of a Hill far distant, through a very good Telescope, you shall find it to wave much like the Sea, and those waves will appear to pass the same way with the wind. ”

“ Even if we watch distant rocks with a telescope, although the surface of the ocean may be as smooth as the surface of a mirror, there is not the slightest visible evidence of what is popularly called a wave. ”

“ 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. ”

“ They laugh at the seaman who tells us of waves a hundred feet in height. Engineers affect to be able to measure the tempest, and to assure us that twenty feet is the utmost height of a wave. On the other hand, an excellent observer assures us, on the testimony of his own sight, that standing in safety on the shore, observing calmly, and in absence of all distraction, he has seen waves that would overtop the towers of Notre Dame, and the heights of Montmartre. ”

“ As the derivative wave, consisting of the large mass of water set in motion by the comparatively small rise and fall of the primary wave, is propagated through the branch oceans, it is affected by many circumstances, such as the continual variation in width between the opposite shores, the alterations in the depth of the channels, and the irregularity of the coast line. ”

“ The light of the firmament comes to us across the direction of the solar rays, and even against the direction of the solar rays; and this lateral and opposing rush of wave-motion can only be due to the rebound of the waves from the air itself, or from something suspended in the air. ”