. The semi-centennial anniversary of the National Academy of Sciences, 1863-1913 . Fig. I. Direct Photograph of the Sun with Dot RepresentingEarth for <f ^ ~ -c ?J/ c ^Ar Fig. 2. Lines of Force of a Magnetized Steel Sphere. THE SEMI-CENTENNIAL ANNIVERSARY 39 When the plate is tapped, to relieve the friction, the particlesfall into place along the lines of force, revealing a characteristicpattern of great beauty. A small compass needle, moved aboutthe sphere, always turns so as to point along the lines of the magnetic poles, it points toward the center of the
. The semi-centennial anniversary of the National Academy of Sciences, 1863-1913 . Fig. I. Direct Photograph of the Sun with Dot RepresentingEarth for <f ^ ~ -c ?J/ c ^Ar Fig. 2. Lines of Force of a Magnetized Steel Sphere. THE SEMI-CENTENNIAL ANNIVERSARY 39 When the plate is tapped, to relieve the friction, the particlesfall into place along the lines of force, revealing a characteristicpattern of great beauty. A small compass needle, moved aboutthe sphere, always turns so as to point along the lines of the magnetic poles, it points toward the center of the between them, at the equator, it is parallel to thediameter joining the poles. As the earth is a magnet, it should exhibit lines of forceresembling those of the sphere. If the magnetic poles coincidedwith the poles of rotation, the north-seeking end of a freelysuspended magnetic needle should point vertically downward atone pole, and vertically upward at the other, and the needleshould be horizontal at the equator. A dip-needle, used tomap the lines of force of the earth, is shown on the screen. Ihave chosen for illustration an instrument designed for
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscience, bookyear1913
