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7//G/J 7'7i > /6'Q UENGY AND HIGH POTENTIAL CURRENTS. 345 X^oq

c x is connected with one of its ends to the line l from the alter-nator g and with the other end to one of the plates c of a con-denser o Ci, the plate (oj) of the latter being connected to a muchlarger plate In this manner both capacity and self-inductionwere adjusted to suit the dynamo frequency.

As regards the rise of potential through resonant action, ofcourse, theoretically, it may amount to anything since it dependson self-induction and resistance and since these may have anyvalue. But in practice one is limited in the selection of thesevalues and besides these, there are other limiting causes. Onemay start with, say, 1,000 volts and raise the e. m. f. to 50 timesthat value, but one cannot start with 100,000 and raise it to tentimes that value because of the losses in the media which aregreat, especially if the frequency is high. It should be possibleto start with, for instance, two volts from a high or low fre-quency circuit of a dynamo and raise the e. m. f. to many hun-dred times that value. Thus coils of the proper dimensionsmight be connected each with only one of its ends to themains from a machine of low e. m. f., and though, the circuit ofthe machine would not be closed in the ordinary acceptance of theterm, yet the machine might be burned out if a proper resonanceeffect would be obtained. I have not been able to produce, norhave I observed with currents from a dynamo machine, suchgreat rises of potential. It is possible, if not probable, that withcurrents obtained from apparatus containing iron the disturbinginfluence of the latter is the cause that these theoretical pos-sibilities cannot be realized. But if such is the case I attributeit solely to the hysteresis and Foucault current losses in the core.Generally it was necessary to transform upward, when the e. m.f. was very low, and usually an ordinary form of induction coilwas employed, but sometimes the arrangement illustrated in Fig.184 II., has been found to be convenient. In this case a coil c ismade in a great many sections, a few of these being used as aprimary. In this manner both primary and secondary are ad-justable. One end of the coil is connected to the line L t fromthe alternator, and the other line l is connected to the intermedi-ate point of the coil. Such a coil with adjustable primary andsecondary will be found also convenient in experiments with thedisruptive discharge. When true resonance is obtained the topof the wave must of course be on the free end of the coil as, forinstance, at the terminal of the phosphorescence bulb ts. This is