Modern electricity and magnetism, theoretically and practically considered (1885)
Avery, Elroy M[cKendree], 1844- [from old catalog] · New York and Chicago, Sheldon and company · leaf 138
Fig. 212. adjoining poles opposite and therefore attracting. If asmall magnetic needle be suspended over the card boardat any point, its length will tend to lie in the directionof the lines of magnetic force at that point as mapped outby the iron filings. («.) The fio:ures may be permanently fixed…
Electricity · Magnetism
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