Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . that, instead of proceeding instraight and parallel lines, they form curves whoseconvexity is turned towards each other. The cur-vature of the lines is greater in proportion to theirproximity; but if the points are placed too neartogether, both currents flow in one track, not sepa-rating until they reach one of the wires connectedwith the outside of the jars. The resistance of theair and other causes often occasion a stream of elec-tricity to follow a
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . that, instead of proceeding instraight and parallel lines, they form curves whoseconvexity is turned towards each other. The cur-vature of the lines is greater in proportion to theirproximity; but if the points are placed too neartogether, both currents flow in one track, not sepa-rating until they reach one of the wires connectedwith the outside of the jars. The resistance of theair and other causes often occasion a stream of elec-tricity to follow a very crooked path in passing overa card. Hence the lines traced by the two currentsin these experiments may be irregular, though thetendency to converge is perfectly evident. 371. Contracting Helix. — The mutual attrac-tion between different portions of the same currentmoving in the same manner, may be rendered evi-dent by the instrument represented in Fig. 160. Awire, coiled into a loose helix, is supported in avertical position by a brass pillar connected withone of the screw-cups on the base board. The lower 20^ 234 DAVIS S end of the helix dips into mercury contained in aglass cup with a metal bottom, by means of which the mercury is brought Fi^. 160. \. .. * into connection with the other the battery isapplied, the portions ofthe current traversingthe different turns ofthe helix of course flowparallel to each other,and in the same direc-tion. Their mutualattractions cause theturns of the helix toapproach each other, shortening it sufficiently to liftthe end of the wire out of the mercury. Thisinterrupts the current, and the helix is lengthenedagain by the elasticity of the wire composing it,producing continued vibration. A spark is seen inthe glass cup at each rupture of contact. It isnecessary to adjust the quantity of mercury so thatthe wire may be raised out of it when the coilshortens itself. 372. A bar magnet passed partly within the helix,a
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
