. The principles of physics. ISOGONIC CtJEVES. 533 Experiment Jf. — We can easily find, as did Columbus, the declinationat any place by the following method : Set up two sticks so that a stringjoining them will lie in the same vertical plane with the Pole Star; thestring will lie in the geographical meridian. Place a long magneticneedle over the string; the angle between the needle and the string is therequired declination. If great accuracy be required, allowance must bemade for the fact that the star is not exactly over the pole, but appearsto describe daily around it a circle whose diameter
. The principles of physics. ISOGONIC CtJEVES. 533 Experiment Jf. — We can easily find, as did Columbus, the declinationat any place by the following method : Set up two sticks so that a stringjoining them will lie in the same vertical plane with the Pole Star; thestring will lie in the geographical meridian. Place a long magneticneedle over the string; the angle between the needle and the string is therequired declination. If great accuracy be required, allowance must bemade for the fact that the star is not exactly over the pole, but appearsto describe daily around it a circle whose diameter is at the present timeabout 2i°. 503. Isogonic curves. —Tl;ese are lines connecting all points. Fig. 417. of equal declination on the earths surface. The line of nodeclination or isogonic of 0° (Fig. 417) commences at the pole about lat. 70°, long. 96°, passes in a south-easterly direction across Lake Erie and Western Pennsyl-vania, and enters the Atlantic Ocean near the boundarybetween the Carolinas. Pursuing its course through thesouth polar regions, it reappears in the eastern hemisphereand crosses Western Australia, the Caspian Sea, and thenceto the Arctic Ocean. There is also a detached line of nodeclination inclosing an oval area in Eastern Asia and thePacific Ocean. In the eastern (or Atlantic) hemisphere. 534 ETHEK DYNAMICS. bounded by the line of no declination, the declination iswestward, as indicated by continuous lines in the the western (or Pacific) hemisphere the declination iseastward, as indicated by dotted lines. The magnetic poles are not fixed objects that can be locatedlike an island or cape, but are constantly changing. Theyappear to
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
