OBTAINING DIRECT FROM ALTERNATING CURRENTS. 411

they offer an appreciable resistance, as the two branches will bethereby better balanced. The translating or other devices to beacted upon by the current are designated by the letters <j, andthey are inserted in the branches c d in any desired manner ; butin order to better preserve an even balance between the branchesdue regard should, of course, be had to the number and characterof the devices.

Figs. 221, 222, 223, and 224 illustrate what may termed “elec-tro-magnetic” devices for accomplishing a similar result—that isto say, instead of producing directly by a generator an electro-motive force in each branch of the circuit, Mr. Tesla establishesa field or fields of force and leads the branches through the samein such manner that an active opposition of opposite effect or di-rection will be developed therein by the passage, or tendency topass, of the alternations of current. In Fig. 221, for example, a is

j

O O

Fig. 221 .

the generator of alternating currents, b b the line circuit, and c nthe branches over which the alternating currents are directed. Ineach branch is included the secondary of a transformer or induc-tion coil, which, since they correspond in their functions to thebatteries of the previous figure, are designated by the letters e f.The primaries h h' of the induction coils or transformers areconnected either in parallel or series with a source of direct orcontinuous currents i, and the number of convolutions is so cal-culated for the strength of the current from i that the cores j s'will be saturated. The connections are such that the conditionsin the two transformers are of opposite character—that is to say,the arrangement is such that a current wave or impulse corres-ponding in direction with that of the direct current in one pri-mary, as h, is of opposite direction to that in the other primary h'.It thus results that while one secondary offers a resistance or op-