Harper's Round Table, January 24, 1882

by Various

If you go to Sandy Hook, or to Rockaway, or Coney Island by boat, you will see some of these things. The wind blows upon the water, and as it moves very easily, a part of the water is pushed up into little heaps by the wind. If the wind is light, these tiny heaps are small, and soon fall down again. When the wind ruffles the water in this way, we call it a ripple. When the wind blows stronger, it pushes up more water, and we call these heaps and ridges waves. As the wind keeps on blowing in the same direction, the heaps rise and fall quickly, and the waves appear to move along over the surface of the water in a great procession. It is really only an appearance. The water does not move along, but only up and down, as the motion started by the wind passes over the surface. However, for our purposes, it is enough to describe things just as they look.

Under the waves the water is calm and still. The huge billows that roll over the sea in storms are seldom much more than fifteen feet high, and they pass over the surface without disturbing the water beyond the depth of a few feet. Every wave has a top, a middle part, and a bottom, or lower part. When a wave coming in from the sea approaches the shore, the bottom of the wave strikes the land first. The sand catches and holds it back and makes it go slower. The top of the wave, not feeling this friction against the ground, rushes forward, leaving the lower part behind. As the wave comes nearer to the beach, the bottom part is held back more and more, and the whole wave tips over. It pitches forward as if tripped up, and the top rushes onward swiftly, while the lower part lags behind. The crest, or upper edge, rises higher, for there is no room for it all to pass, and it lifts up as if trying to stand upright. The air gets caught under the crest of the wave in front, and in a moment the wave, unable to rise any higher, falls flat on its face upon the sand. The air caught under it bursts out with a roaring sound, and escapes through the water in a million white bubbles that make the water look like milky foam.

The white-caps you see upon the open water are made in the same way. The wind seems to be impatient that the waves move so slowly, and it knocks their caps off, and the poor waves seem to get very mad about it, and to grow quite white in the face. The top of the wave tries to rush ahead of the lower part, and tumbles over in the foaming water-fall the sailors call a white-cap.

When a wave reaches the shore, something very curious happens. The bottom of the wave strikes the ground first. The wave drags over the sand as it passes on toward the beach, and draws some of the loose sand after it. First, the smaller and lighter grains are rolled along or lifted up and carried a short distance by the wave. As the water grows more shallow, the wave scrapes and drags over the sand, and the larger grains and even small pebbles are rolled along after the lighter sand. But the wave must go slower here, and thus it lets go its hold and drops its load. When it has passed, the sand, that may have been level before, is raised into a low ridge or windrow. The smaller and lighter grains, being carried farthest, are dropped in one place, and the heavier grains and small pebbles are dropped in another place.

The next wave may stir up and drag along more sand, and lay it down, all sorted out, on the ridge. Other waves may follow, and do the same thing, and so the heap begins to grow: the baby sand-bar has been born. It may have been a mere trifle that started it just there—a crab or the bones of a dead fish, some gravel dropped from a piece of melting ice, a stray bit of sea-weed. No matter what it was, or how trifling the obstruction, the loose sand rolled along by the wave caught just there, and was left behind; the next wave left a little more, and each in turn added to the heap.

Waves are very irregular in size, and perhaps some big fellow may lift up more sand than he can carry, and may drop it all in one place. Then for some time the weather may be pleasant, and the tiny ridge, perhaps not a quarter of an inch high, and twenty feet wide, may rest awhile. Then a storm comes, with large waves, and when they meet this slight obstruction they go over it more slowly, and drop part of their loads upon it. So it may grow very fast in a single day. In front, toward the sea, the sand will be scooped out in long trenches, and behind it will be a stretch of deeper and smoother water. After that every wave that comes in stumbles and appears to trip just there, and there are white-caps over that spot even in pleasant weather. When the smooth swelling rollers are coming in from the sea, they appear to be angry every time they strike their feet on the hidden bar, and they tumble over with a roar, and show a white feather of foam in their caps.

The sand-bar, once started, never stops growing or changing. It grows wider and higher, or it changes its shape, twisting about in the strangest manner. Smaller bars spring up upon it, or disappear only to grow up in another place. At last, some spring day, when the tides run low, the bar appears above the water. Strange things have happened to it. The fish have made it their home, lively crabs scamper about on the wet sand, and thousands of clams find a snug resting-place there.

FINGERS OF THE SEA.

One day last summer I found one of these young sand-bars cast up by a storm at the eastern point of Coney Island, near the inlet at the end of the Marine Railway. It was so strange that I took a shot at it with my camera, and here it is. It is a very small affair, and you may not be able to find it next summer, for I dare say the next storm tore it all to pieces, or carried it away and put it somewhere else.