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SUDDEN CHANGES OF DEPTH.
21
are no frosts^to'break off projecting peaks, no lightnings to split, no glaciers to carry them or crumble them away, no meteoric influences to corrode and round them. Nevertheless, if there are not in the sea, as on
the land, agencies like these, ceaselessly at work leveling projections,
there are others- which as ceaselessly labor to smooth the asperities of
the surface. There are the sedimentary deposits brought down by the
rivers, and innumerable millions of the skeletons of animalcula?, which live
in the deep, or fall like snow from the upper strata of the water and
gradually fiU'up the submarine valleys. Those fantastic mountain chains
drawn on the bed of the sea by Buache and other geographers can not,
therefore, really exist, since the geological agencies at work under water
differ from those which carve out the table-lands and mountains on our
continents. If some immense eddy prevented the particles from being
deposited in the deep parts of the ocean, then the rocks and the rifts of
the abysses would keep their first form, like those peaks and craters of
the moon which are not worn away by the inclemencies of an atmosphere.
There are, indeed, tracts in the sea where, perhaps from the influence of
a submarine counter-current, the rocks of the bottom are not covered by
organic alluvium. In the deepest part of that great arm of the sea which
separates the Faroe Islands Horn Great Britain, Wallich drew up from a
depth of more than 600 fathoms* a large fragment of quartz detached
from the living rock, and several pieces of basalt; it is quite possible,
however, that these fragments had been dropped there by an iceberg.
In general, the sea-bed extends for wide spaces in long undulations and
gentle slopes. Sailors, who are carried swiftly over the water by wind
or steam, and who generally take soundings at places far distant from one
another, are tempted to exaggerate the magnitude of inequalities in the
sea-bed, and to see chasms and precipices, where the declivity is in reality
inconsiderable. Escarpments, similar to those of the continental mountains, very rarely present themselves; Fitzroy was,*greatly surprised to
find in the neighborhood of the Abrolhos, near Brazil, such rapid slopes,
that the lead on one side of the ship indicated from 4 to 6 fathoms only,
while on the other side it marked from 16 to 22 fathoms. Sometimes a
special cause explains these abrupt changes of the level. Thus M. de
Villeneuve-Flayosc discovered in the Gulf of Cannes, a spring of fresh
water springing from the depths of a kind of well, the sides of which
sloped at an angle of 27 degrees. But how can we explain that singular
gulf which extends immediately in front of Cape Breton, on the coast of
the Landes ? Ought we to attribute its formation to the meeting of the
tides, which takes place in the channel of the Gulf of Gascony ? This is
a question which it is not yet possible to decide.
We can form some notion of the submarine tracts by surveying the
countries that have emerged from under water at a comparatively recent
epoch. The Landes of France, the low lands which have replaced the
* Marine soundings are always taken in fathoms; a fathom is equivalent to 2 yards, or 6
feet linear.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000026 |
| Type | Books/Pamphlets |
| Transcript | SUDDEN CHANGES OF DEPTH. 21 are no frosts^to'break off projecting peaks, no lightnings to split, no glaciers to carry them or crumble them away, no meteoric influences to corrode and round them. Nevertheless, if there are not in the sea, as on the land, agencies like these, ceaselessly at work leveling projections, there are others- which as ceaselessly labor to smooth the asperities of the surface. There are the sedimentary deposits brought down by the rivers, and innumerable millions of the skeletons of animalcula?, which live in the deep, or fall like snow from the upper strata of the water and gradually fiU'up the submarine valleys. Those fantastic mountain chains drawn on the bed of the sea by Buache and other geographers can not, therefore, really exist, since the geological agencies at work under water differ from those which carve out the table-lands and mountains on our continents. If some immense eddy prevented the particles from being deposited in the deep parts of the ocean, then the rocks and the rifts of the abysses would keep their first form, like those peaks and craters of the moon which are not worn away by the inclemencies of an atmosphere. There are, indeed, tracts in the sea where, perhaps from the influence of a submarine counter-current, the rocks of the bottom are not covered by organic alluvium. In the deepest part of that great arm of the sea which separates the Faroe Islands Horn Great Britain, Wallich drew up from a depth of more than 600 fathoms* a large fragment of quartz detached from the living rock, and several pieces of basalt; it is quite possible, however, that these fragments had been dropped there by an iceberg. In general, the sea-bed extends for wide spaces in long undulations and gentle slopes. Sailors, who are carried swiftly over the water by wind or steam, and who generally take soundings at places far distant from one another, are tempted to exaggerate the magnitude of inequalities in the sea-bed, and to see chasms and precipices, where the declivity is in reality inconsiderable. Escarpments, similar to those of the continental mountains, very rarely present themselves; Fitzroy was,*greatly surprised to find in the neighborhood of the Abrolhos, near Brazil, such rapid slopes, that the lead on one side of the ship indicated from 4 to 6 fathoms only, while on the other side it marked from 16 to 22 fathoms. Sometimes a special cause explains these abrupt changes of the level. Thus M. de Villeneuve-Flayosc discovered in the Gulf of Cannes, a spring of fresh water springing from the depths of a kind of well, the sides of which sloped at an angle of 27 degrees. But how can we explain that singular gulf which extends immediately in front of Cape Breton, on the coast of the Landes ? Ought we to attribute its formation to the meeting of the tides, which takes place in the channel of the Gulf of Gascony ? This is a question which it is not yet possible to decide. We can form some notion of the submarine tracts by surveying the countries that have emerged from under water at a comparatively recent epoch. The Landes of France, the low lands which have replaced the * Marine soundings are always taken in fathoms; a fathom is equivalent to 2 yards, or 6 feet linear. |
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