Magnetic Poles of the Earth—Variation of the Magnetic Needle—Phenomena of the Northern Lights. Captain Ross, an English navigator, left England about twenty years ago, in pursuit of the north magnetical pole. He followd the magnetical needle, directing its course westwardly till he arrivd at Baffin’s bay in America, where he left his ship and traveld about two hundred miles still farther west, at which place he determind to be the north magnetic pole. This point being several hundred miles south of the north geographical pole, determines its opposite or south magnetical pole to be an equal distance north of the south geographical pole, though on the opposite side of the earth. From the north magnetic pole southward, the line of coincidence, or line of no variation as it is sometimes calld, passes through Hudson’s bay, the state of Michigan, Ohio, and the several states lying south of these. This line forms a perfect The variation of the magnetic needle in Oregon, among other things, has attracted my attention. Surveyors of this country tell me that the magnetical needle varies to the right of the geographical pole about 19 deg. and 20 min. Some, however, have observd in different places a variation of more than 20 degrees. This difference may be accounted for, by the great amount of iron disseminated through the country. I have taken the trouble to draw a diagram of a section of the earth, to ascertain what the variation of the magnetic needle would be geometrically, at Oregon city. This corresponds, to a considerable degree of nearness, with experiments made with the compass. Concerning the depth to which the magnetic pole is seated in the earth, I have no means of ascertaining. This could best be done with a dipping needle along the line of no variation, at a suitable distance from the equator, so that the north end of the needle may have a perfect freedom of dip. Let the distance be ascertaind from the observer to the north magnetic pole, as manifested at the surface, which differs not much from two hundred miles, west of Baffin’s bay. This distance may form the base line of a right-angled triangle. Let the surface angle at the magnetic pole be the right angle, and the dipping needle will show the angle at the place of the observer between the line on the surface of the earth and the line made by the dip. The observer then has a right-angled triangle, with sufficient data to ascertain at what depth the magnetic pole lies below the surface of the earth. It would be gratifying to me, if some philosopher along the line of coincidence would take the trouble to ascertain the depth of the magnetic pole, and publish his experiments. Possibly, some day, a knowledge of that fact may add to the light of science. The reasons why the magnetic needle at some places on the earth has a stationary variation from the geographical pole, and at others an annual movable variation, seems by some to be not easily accounted for, but I am of opinion that the same reasons may be assigned for the stationary position of the needle that are assigned for the stationary appearance of a planet in its orbit around the sun. The motion of the magnetic pole around the earth, to an observer at any one point on the earth, as at London at present, presents during its whole circuit two stationary points or extremes to the left in its forward, and to the right in its retrograde movement. The extreme slowness of the magnetic pole round the earth, causes the stationary variation of the needle to remain nearly the same for a great many years. Hence so long as the magnetic pole continues to revolve around the earth, every other place on the earth will give in its turn a stationary and an annual variation. Soon after my arrival at Oregon city, in the fall of the year, I observd that the central portion of that body of light calld Aurora Borealis, was as much to the right of the north geographical pole as the variation of the magnetic needle. I was then led to conclude that it was a constant attendant upon the north magnetical pole, moving westward gradually as the magnetic pole advances in that direction. Very evidently the Northern Lights are occasiond by emissions of electrical light flowing from the great amount of electricity concentrated at the north magnetical pole. Decorative glyph
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