00000357 |
Previous | 357 of 595 | Next |
|
small (250x250 max)
medium (500x500 max)
Large
Extra Large
large ( > 500x500)
Full Resolution
All (PDF)
|
326 THE ATMOSPHERE AND METEOROLOGY.
space toward unknown regions of the heavens, the approach of a perturbing planet, every thing, even the friction of the earth on the vapors
which surround it, incessantly develop the magnetic energy ofthe globe,
as an immense coil traversed by most powerful electric currents would
do. In the ground which seems so impassive, but where so many germs
give birth to life, whence so many wonders spring, the mysterious current circulates without ever resting, like an inexhaustible river. Under
the influence of the sun, it hastens or slackens its speed, moves in one direction or the other, and travels over the circumference of the globe, its
equator and its poles. It obeys unceasingly the harmonious laws of nature, while only seeming to act capriciously because of the manifold interruptions causing the apparent irregularity in the succession of its periodicities. Just as the fine magnetic needle trembles and shakes like an
affrighted creature in its box suspended at the ship's helm, so all over the
earth magnetic currents oscillate and move untiringly; directly obeying
the cosmical influences which make themselves only slowly felt on other
functions of the globe, they may rightly be compared to the nervous
phenomena in the animal organism. In consequence of their continual
vibratory motion, the magnetic currents can not be clearly traced on*the
map, and we must always confine ourselves to indicating their mean direction. There are not two instants in the year when the movements of
the needle are identical on the surface of the earth.
The poles toward which the compass points in the two hemispheres
stray constantly around the astronomical poles of the planet, and it is
never at the same point that their precise position must be sought for.
In 1832 Captain John Ross, then sailing in the midst of the polar archipelago of North America, arrived in the neighborhood of the north pole
ofthe compass, since the point of his instrument was directed almost vertically to the earth. This point, toward which all the magnetic currents
ofthe northern hemisphere then converged, was situated in the peninsula
of Boothia Felix, nearly twenty degrees to the south of the terrestrial pole
(70° 5' N.), and at more than ninety-nine degrees to the west ofthe meridian of Paris; but since that epoch it has probably moved a few degrees to
the east. The magnetic pole ofthe south has not been discovered by any
navigator up to the present time. But according to the calculations of
Duperrey, Gauss, and other savants, it would probably be found at fourteen degrees fifty-five minutes from the Antarctic Pole to the south ofthe
continent of Australia. The two points of attraction of the magnet are
thus each situated at the meridian of a group of continents; but they are
not antipodal to one another, since they are found in the same hemisphere
separated from one another by an arc of little more than one hundred
and sixty-one degrees—twenty-nine degrees less than the semi-circumference. As to the magnetic equator, which is the line where the needle
keeps perfectly horizontal to the surface of the earth, it is no more to be
confounded with the equator of rotation than the magnetic poles with the
extremities ofthe planetary axis. It follows a curved line which cuts the
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000357 |
| Type | Books/Pamphlets |
| Transcript | 326 THE ATMOSPHERE AND METEOROLOGY. space toward unknown regions of the heavens, the approach of a perturbing planet, every thing, even the friction of the earth on the vapors which surround it, incessantly develop the magnetic energy ofthe globe, as an immense coil traversed by most powerful electric currents would do. In the ground which seems so impassive, but where so many germs give birth to life, whence so many wonders spring, the mysterious current circulates without ever resting, like an inexhaustible river. Under the influence of the sun, it hastens or slackens its speed, moves in one direction or the other, and travels over the circumference of the globe, its equator and its poles. It obeys unceasingly the harmonious laws of nature, while only seeming to act capriciously because of the manifold interruptions causing the apparent irregularity in the succession of its periodicities. Just as the fine magnetic needle trembles and shakes like an affrighted creature in its box suspended at the ship's helm, so all over the earth magnetic currents oscillate and move untiringly; directly obeying the cosmical influences which make themselves only slowly felt on other functions of the globe, they may rightly be compared to the nervous phenomena in the animal organism. In consequence of their continual vibratory motion, the magnetic currents can not be clearly traced on*the map, and we must always confine ourselves to indicating their mean direction. There are not two instants in the year when the movements of the needle are identical on the surface of the earth. The poles toward which the compass points in the two hemispheres stray constantly around the astronomical poles of the planet, and it is never at the same point that their precise position must be sought for. In 1832 Captain John Ross, then sailing in the midst of the polar archipelago of North America, arrived in the neighborhood of the north pole ofthe compass, since the point of his instrument was directed almost vertically to the earth. This point, toward which all the magnetic currents ofthe northern hemisphere then converged, was situated in the peninsula of Boothia Felix, nearly twenty degrees to the south of the terrestrial pole (70° 5' N.), and at more than ninety-nine degrees to the west ofthe meridian of Paris; but since that epoch it has probably moved a few degrees to the east. The magnetic pole ofthe south has not been discovered by any navigator up to the present time. But according to the calculations of Duperrey, Gauss, and other savants, it would probably be found at fourteen degrees fifty-five minutes from the Antarctic Pole to the south ofthe continent of Australia. The two points of attraction of the magnet are thus each situated at the meridian of a group of continents; but they are not antipodal to one another, since they are found in the same hemisphere separated from one another by an arc of little more than one hundred and sixty-one degrees—twenty-nine degrees less than the semi-circumference. As to the magnetic equator, which is the line where the needle keeps perfectly horizontal to the surface of the earth, it is no more to be confounded with the equator of rotation than the magnetic poles with the extremities ofthe planetary axis. It follows a curved line which cuts the |
|
|
|
|
|
|
| B |
|
| C |
|
| G |
|
| H |
|
| M |
|
| T |
|
| U |
|
| Y |
|
|
|
