This extract includes two sections from the full article, which also foresaw such advances in electrical usage as fluorescent lighting, heating and cooling. Donahoe's Magazine, March, 1893, pages 291-292:
THE FUTURE OF ELECTRICITY.
BY PROF. A. E. DOLBEAR.
Telegraph- ing without Wires.
For many years telegraphic work was carried on in what is technically called a closed circuit, which means a continuous electrical conductor from the generator through the telegraphic instrument back to the generator. The ground has often been made a part of this circuit. When the telephone began to be used it was noticed that telegraphic signals could often be heard coming from circuits wholly disconnected, sometimes even a mile or two away. Professor Trowbridge of Harvard, showed how it was possible to telegraph across a river or even the Atlantic Ocean without having any connecting cable. An electric current in the earth spreads out in a wonderful way from its ground terminals, and when it comes to a conductor better than the earth a larger proportion will follow it wherever it may lead; hence a part of a current sent into the earth at one place may be utilized in another circuit quite apart from it, and the further apart the earth terminals of the first circuit the greater distance away may the second circuit be. Now if a telegraphic circuit had one terminal in, say Greenland, and the other in Brazil, and another circuit had its terminals, say in Norway and Liberia in Africa, any electric current in one would be felt in the other, and signals with a Morse key made in one might be heard in a telephone in the other circuit. Such effects are due to conduction in the earth, and the observed phenomena has served to show that an intermediate wire is not essential for telegraphic communication. It was shown by the writer some years ago that a conducting circuit was not essential for electrical processes, for telegraph signals and talking have been heard in a telephone quite disconnected from any circuit, and fifty feet away from the nearest, and subsequently he found it possible to set up rapidly intermittent currents between two places several hundred feet apart, by discharging opposite terminals of induction coils into the earth, the second terminal of each coil being in the air so that telegraphic signals could be heard in one circuit without what is called a complete circuit in either apparatus. There is no special limit to this method.
Maxwell pointed out from theoretical considerations more than twenty years ago, that what we call light was probably electro-magnetic in quality, and a few years ago Hertz showed how to produce such waves five hundred thousand times longer than common light waves; also that such waves were reflected and refracted like light with proper lenses. A beam from what is called a search light can be directed and may be seen in clear air in the night a hundred miles or more away. In murky air and fog such light is quickly absorbed, but the longer artificial waves are not thus affected. A beam of Hertzian rays can be thus directed and not suffer so great loss, and being received by a proper electrical apparatus can be made visible; signals thus can be sent where the eye can see nothing in the space, and curiously enough such substances as wood and brick walls are transparent to such waves. There is no limit to this method but the curvation of the earth and the delicacy of the receiving apparatus.
Another method of signalling depending upon electrical conditions will probably be common in a short time; namely, by projecting a beam of light from a powerful electric arc upon the sky or clouds. Such a shaft of light directed upwards can be seen many miles, and by making it intermittent a code of signals can be made useful, say for the weather bureau, in announcing the probabilities for the next day. Lighthouses and vessels at sea can thus indicate their whereabouts when direct light would be cut off by dense fog. With the aid of a long focus lens we shall soon see all sorts of advertisements and fantastic shapes in the sky.
Are the planets inhabited? This question every thoughtful person must often ask himself. The distances between the earth and even the nearest is so immense to appall one to think of.
When our telescopes have apparently reduced the distance a thousand times they are still too remote to see any evidence of the existence of intelligent beings. If there was a city on Mars the size of London it would seem but a speck not distinguishable from other areas. If such a city had electric arc lights such as we possess, it seems very certain they would sometimes be seen with our larger telescopes, and in like manner their inhabitants could sometimes see our lights if provided with as good telescopes as ours.
With a good search light with a million candle power or more directed towards Mars, the beam could be made intermittent and signals could be sent the same as between two mountains. If such search lights were sent from the tops of high mountains here, the atmosphere would not absorb so much as it does at lower levels. Once out of the air, there would be no loss from absorption and the beam would fly on, taking but about four minutes to reach Mars when nearest to us. With similar facilities in Mars there would be no trouble in sending and receiving signals. We have the necessary outfit; it only waits for the placing and patient testing. If no response was made it might signify only that there was no observer there when we were signalling, or that there was no electric light known there or no telescope. It may be drawing a long bow, but I will venture to add that what I have already spoken of as Hertzian waves of greater length than light waves can in like manner be directed to Mars or elsewhere, and there is nothing in the nature of things to hinder electric signalling between planets. One cannot but speculate upon the effect on the civilized world of the first signal from Mars or elsewhere, whether its full significance was understood or not, and one may well reflect upon what question he would like to have first answered by an inhabitant of another world if he could expect an answer. Are there not philosophies that could be exploded with such an electric signal? In any case, many would be made glad and many made sad.