. The science-history of the universe . field conductors can be set rotating, as was firstsuggested by Baily in 1879. Consider an ordinary Gramme ring (Fig. 17) woundwith a continuous winding. If a single alternating currentwere introduced at the points A A it would set up an oscil-latory magnetic field, a N pole growing at A, and a S poleat A, then dying away and reversing in direction. Simi-larly, if another alternate current were introduced at B B 200 ELECTRICITY it would produce another oscillatory magnetic field in theB B diameter. If both these currents are set to work buttimed so that t

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. The science-history of the universe . field conductors can be set rotating, as was firstsuggested by Baily in 1879. Consider an ordinary Gramme ring (Fig. 17) woundwith a continuous winding. If a single alternating currentwere introduced at the points A A it would set up an oscil-latory magnetic field, a N pole growing at A, and a S poleat A, then dying away and reversing in direction. Simi-larly, if another alternate current were introduced at B B 200 ELECTRICITY it would produce another oscillatory magnetic field in theB B diameter. If both these currents are set to work buttimed so that the B B current is *% period behind the A Acurrent, they will then combine to produce a rotatory mag-netic field, tho the coil itself stands still. This is quiteanalogous to the well-known way in which a rotatory mo-tion, without any dead points, can be produced from twooscillatory motions by using two cranks at right angles toone another, the impulses being given l/$ period one afterthe other. The above combination is called a diphase.

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