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TEMPERATURE OF THE SEA.
43
to the waters of the Mediterranean can attain. In the tropical latitudes
of the Atlantic and the South Sea, the azure of the ocean is no less beautiful than that of the Tyrrhenian Sea; while in the direction of the poles
the water gradually assumes a greenish tint. Naturalists have concluded from this fact that the refraction of the rays of light, which are
much more vivid under tropical latitudes, play a principal part in the
blue coloring of the sea. Maury thinks that the saltness is also one of
the causes which contributes the most to give its azure tint to the water ; and observes that the Gulf Stream of the American coasts, superior
in salinity and in temperature to the water around it, is also of a much
deeper blue. In the same way the shallow water let into the salt marshes
of coasts gains in intensity of color in proportion as the salt is concentrated there. Still, it is very possible that the coloring of the sea is due
in great part, like the marvelous tints of the Swiss lakes,* to innumerable
corpuscules held in suspension, upon which the light strikes. '
The law of the distribution of temperature, in the depth of the ocean,
is not as yet more determined than that of the coloring of the water.
At the surface of the sea it is as easy to make observations as in the air,
and it has been determined, without difficulty, that this superficial sheet
of water presents, on an average, in all climates, the same degree of heat
as the superincumbent atmosphere. Thus, from the polar regions to the
equatorial zone, the water becomes warmer with an almost regular gradation, and, from the freezing-point under the Arctic circle, the temperature
rises to 68 and 77 degrees Fahr. under the tropics, and to 86 and even
above 90 degrees Fahr. in the Pacific, the Red Sea, and the Indian Ocean.f
With regard to the increase or decrease of heat in a vertical direction, we
had till recently only the vaguest notions, in consequence of the want
of exact soundings. It is, in fact, very difficult to lower to a depth of
several hundred, and even several thousand fathoms, thermometrical apparatus strong enough to resist the enormous pressure of one atmosphere for every 33 feet.
Sir James Ross was one of the first who attempted to apply the resources of modern science to a systematic exploration of the temperature
in the depths of the sea; but he seems to have committed the error of
generalizing too hastily from the incomplete results which he had obtained ; and, in his eagerness, he believed he had discovered a law which the
subsequent researches of navigators have not confirmed. He thought
that he could establish the fact that under the equator the temperature
of the water diminishes gradually to 1200 fathoms, where it is only 39*2
degrees Fahr. On each side of the equator the upper waters gradually
cool, and the limit of four degrees is progressively raised toward the surface ; it is at the fiftieth degree of latitude, in the southern hemisphere,
that it finally reaches the level of the sea. Farther in the direction of
the pole the superficial water continues to grow colder, while the line of
four degrees sinks gradually to the depth of 765 fathoms. Thus, as the
* See the section entitled Lakes. f Eitzroy, Weather-Book, p. 84.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000050 |
| Type | Books/Pamphlets |
| Transcript | TEMPERATURE OF THE SEA. 43 to the waters of the Mediterranean can attain. In the tropical latitudes of the Atlantic and the South Sea, the azure of the ocean is no less beautiful than that of the Tyrrhenian Sea; while in the direction of the poles the water gradually assumes a greenish tint. Naturalists have concluded from this fact that the refraction of the rays of light, which are much more vivid under tropical latitudes, play a principal part in the blue coloring of the sea. Maury thinks that the saltness is also one of the causes which contributes the most to give its azure tint to the water ; and observes that the Gulf Stream of the American coasts, superior in salinity and in temperature to the water around it, is also of a much deeper blue. In the same way the shallow water let into the salt marshes of coasts gains in intensity of color in proportion as the salt is concentrated there. Still, it is very possible that the coloring of the sea is due in great part, like the marvelous tints of the Swiss lakes,* to innumerable corpuscules held in suspension, upon which the light strikes. ' The law of the distribution of temperature, in the depth of the ocean, is not as yet more determined than that of the coloring of the water. At the surface of the sea it is as easy to make observations as in the air, and it has been determined, without difficulty, that this superficial sheet of water presents, on an average, in all climates, the same degree of heat as the superincumbent atmosphere. Thus, from the polar regions to the equatorial zone, the water becomes warmer with an almost regular gradation, and, from the freezing-point under the Arctic circle, the temperature rises to 68 and 77 degrees Fahr. under the tropics, and to 86 and even above 90 degrees Fahr. in the Pacific, the Red Sea, and the Indian Ocean.f With regard to the increase or decrease of heat in a vertical direction, we had till recently only the vaguest notions, in consequence of the want of exact soundings. It is, in fact, very difficult to lower to a depth of several hundred, and even several thousand fathoms, thermometrical apparatus strong enough to resist the enormous pressure of one atmosphere for every 33 feet. Sir James Ross was one of the first who attempted to apply the resources of modern science to a systematic exploration of the temperature in the depths of the sea; but he seems to have committed the error of generalizing too hastily from the incomplete results which he had obtained ; and, in his eagerness, he believed he had discovered a law which the subsequent researches of navigators have not confirmed. He thought that he could establish the fact that under the equator the temperature of the water diminishes gradually to 1200 fathoms, where it is only 39*2 degrees Fahr. On each side of the equator the upper waters gradually cool, and the limit of four degrees is progressively raised toward the surface ; it is at the fiftieth degree of latitude, in the southern hemisphere, that it finally reaches the level of the sea. Farther in the direction of the pole the superficial water continues to grow colder, while the line of four degrees sinks gradually to the depth of 765 fathoms. Thus, as the * See the section entitled Lakes. f Eitzroy, Weather-Book, p. 84. |
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