This investigation, then, it goes without saying, deals with alternating currents, and, to be more precise, with alternating currents of high potential and high frequency.  Just in how much a very high frequency is essential for the production of the results presented is a question which even with my present experience, would embarrass me to answer.  Some of the experiments may be performed with low frequencies; but very high frequencies are desirable, not only on account of the many effects secured by their use, but also as a convenient means of obtaining, in the induction apparatus employed, the high potentials, which in their turn are necessary to the demonstration of most of the experiments here contemplated.

Of the various branches of electrical investigation, perhaps the most interesting and immediately the most promising is that dealing with alternating currents.  The progress in this branch of applied science has been so great in recent years that it justifies the most sanguine hopes.  Hardly have we become familiar with one fact, when novel experiences are met with and new avenues of research are opened.  Even at this hour possibilities not dreamed of before are, by the use of these currents, partly realized.  As in nature all is ebb and tide, all is wave motion, so it seems that; in all branches of industry alternating currents—­electric wave motion—­will have the sway.

One reason, perhaps, why this branch of science is being so rapidly developed is to be found in the interest which is attached to its experimental study.  We wind a simple ring of iron with coils; we establish the connections to the generator, and with wonder and delight we note the effects of strange forces which we bring into play, which allow us to transform, to transmit and direct energy at will.  We arrange the circuits properly, and we see the mass of iron and wires behave as though it were endowed with life, spinning a heavy armature, through invisible connections, with great speed and power—­with the energy possibly conveyed from a great distance.  We observe how the energy of an alternating current traversing the wire manifests itself—­not so much in the wire as in the surrounding space—­in the most surprising manner, taking the forms of heat, light, mechanical energy, and, most surprising of all, even chemical affinity.  All these observations fascinate us, and fill us with an intense desire to know more about the nature of these phenomena.  Each day we go to our work in the hope of discovering,—­in the hope that some one, no matter who, may find a solution of one of the pending great problems,—­and each succeeding day we return to our task with renewed ardor; and even if we are unsuccessful, our work has not been in vain, for in these strivings, in these efforts, we have found hours of untold pleasure, and we have directed our energies to the benefit of mankind.

We may take—­at random, if you choose—­any of the many experiments which may be performed with alternating currents; a few of which only, and by no means the most striking, form the subject of this evening’s demonstration:  they are all equally interesting, equally inciting to thought.