Elementary lessons in electricity and magnetism (1906)
Thompson, Silvanus P. (Silvanus Phillips), 1851-1916, Schwetzky, Otto H. L. [from old catalog] · Chicago, Thompson & Thomas · leaf 65
in goodworking order, and capable of giving, say, sparks fourinches long when the knuckle is presented to the knob,it will be found that, on fastening a fine pointed needle 1 Invented in 1752 by Franklin, for the purpose of warning him of thepresence of atmospheric electricity, drawn from the air… … Fig. 26. drawn at the knob, while a fine jet or brush of paleblue light will appear at the point. If a lighted taperbe held in front of the point,the flame will be visibly blo^^^laside (Fig. 26) by the streamsof electrified air repelled fromthe point. These air-currentscan be felt with the…
Electricity · Magnetism
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