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64 THE OCEAN.
springing from the depths of the ocean, advance abruptly upon its sloping beaches, destroying all they encounter on their way.
It is along the shores of continents and around rocky islands that ordinary waves and heavy surf appear in all their grandeur and assume dimensions truly formidable. In accordance with the more or less gradual
inclination of the bottom to the shore, a wave coming from the open sea
rolls over a bed more and more shallow, and mus't perforce slacken its
speed; but at the same time, it increases by its own depth the stratum
of water which it overflows, and consequently the wave which follows it
is subjected to less retardation of the impulsive force. The second wave
constantly gains on the first, and finally reaches it, swelling its crest, and,
slackening its own speed in its turn, gives a third wave time to distance
it also. Finally, near the strand, the liquid mass, swelled by the pursuing
waves, and unable to spread out farther at its base along the shore, which
is too near, gains in height what it wants in breadth, and, rising like a
wall, it bends over with a wide curve in front, and breaks with a thundering sound, throwing water, mixed with sand and foam, far along the
shore. This surge, which is dreadful indeed during tempests, rises much
higher than the waves; to the ancients the whitening billows of the open
sea, whose crests were seen to shine, like the fleeces of sheep, were the
flocks of Proteus; while the waves of the shore, still called in our days
cavalli and cavalloni by the people of the south of Europe, were the
foaming horses of Neptune.
The height to which the crests of some of these waves attain when the
configuration of the coast favors the movement, seems sometimes to partake of the marvelous. The mass of water which rises vertically can
then only be compared to an ascending cataract. Spallanzani relates
that sometimes, in violent tempests, the waves reach half-way up, or even
to the top, of Stromboluzzo, a peak of lava which rises near Stromboli,
318 feet above the mean level of the sea. The Bell Rock light-house,
which rises boldly to 112 feet in height on a rock off the Scottish coast,
is often enveloped in waves and foam even long after the tempest has
ceased to disturb the sea.* Smeaton, too, has seen waves covering the
Eddystone light-house, and leaping in a spout of water 82 feet above the
lantern; the mass which is thus raised around the edifice can not be less
than from 2616 to 3924 cubic yards, and would weigh as much as a large
three-decker. After these great storms, salt pools are scattered here and
there on the top of the cliffs.
The pressure exerted by these masses of water, hurled with such impetus, is no less surprising. Thomas Stephenson ascertained that the force
of the sea dashed against the Bell Rock light-house amounted to about
17 tons for every square yard. In the Island of Skerryvore the heaviest
calculated pressure is about three tons and a half for every yard—that is
to say, more than 6^- lbs. avoirdupois for every 0*16 of a square inch.
With such a force the displacement of blocks which seem enormous to us
* Mrs. Somerville, Physical Geography.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000073 |
| Type | Books/Pamphlets |
| Transcript | 64 THE OCEAN. springing from the depths of the ocean, advance abruptly upon its sloping beaches, destroying all they encounter on their way. It is along the shores of continents and around rocky islands that ordinary waves and heavy surf appear in all their grandeur and assume dimensions truly formidable. In accordance with the more or less gradual inclination of the bottom to the shore, a wave coming from the open sea rolls over a bed more and more shallow, and mus't perforce slacken its speed; but at the same time, it increases by its own depth the stratum of water which it overflows, and consequently the wave which follows it is subjected to less retardation of the impulsive force. The second wave constantly gains on the first, and finally reaches it, swelling its crest, and, slackening its own speed in its turn, gives a third wave time to distance it also. Finally, near the strand, the liquid mass, swelled by the pursuing waves, and unable to spread out farther at its base along the shore, which is too near, gains in height what it wants in breadth, and, rising like a wall, it bends over with a wide curve in front, and breaks with a thundering sound, throwing water, mixed with sand and foam, far along the shore. This surge, which is dreadful indeed during tempests, rises much higher than the waves; to the ancients the whitening billows of the open sea, whose crests were seen to shine, like the fleeces of sheep, were the flocks of Proteus; while the waves of the shore, still called in our days cavalli and cavalloni by the people of the south of Europe, were the foaming horses of Neptune. The height to which the crests of some of these waves attain when the configuration of the coast favors the movement, seems sometimes to partake of the marvelous. The mass of water which rises vertically can then only be compared to an ascending cataract. Spallanzani relates that sometimes, in violent tempests, the waves reach half-way up, or even to the top, of Stromboluzzo, a peak of lava which rises near Stromboli, 318 feet above the mean level of the sea. The Bell Rock light-house, which rises boldly to 112 feet in height on a rock off the Scottish coast, is often enveloped in waves and foam even long after the tempest has ceased to disturb the sea.* Smeaton, too, has seen waves covering the Eddystone light-house, and leaping in a spout of water 82 feet above the lantern; the mass which is thus raised around the edifice can not be less than from 2616 to 3924 cubic yards, and would weigh as much as a large three-decker. After these great storms, salt pools are scattered here and there on the top of the cliffs. The pressure exerted by these masses of water, hurled with such impetus, is no less surprising. Thomas Stephenson ascertained that the force of the sea dashed against the Bell Rock light-house amounted to about 17 tons for every square yard. In the Island of Skerryvore the heaviest calculated pressure is about three tons and a half for every yard—that is to say, more than 6^- lbs. avoirdupois for every 0*16 of a square inch. With such a force the displacement of blocks which seem enormous to us * Mrs. Somerville, Physical Geography. |
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