Dodge, Mary Mapes, 1830-1905 · [New York : Scribner & Co.] · leaf 178
FIG. 3. ABOUT MAGNETS. 711 … are shown more clearly when a horseshoe mag-net is used, because the poles are near eachother. These curved lines are called lines offorce, because they indicate the direction of themagnetic force. But you must not think that the lines of forcehave any real existence, any more than themeridians and…
Children's literature
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