“The coal,” said he, “was an excellent makeshift for temporary use until a more enduring supply of power was discovered to supersede it. But even now it could if necessary be almost entirely dispensed with and yet there are still vast deposits of it untouched. In the long distant future the time will come when the coal will be regarded as a deposit of food for your race as it is now with ours, but it will not be consumed for its heat or its power except in that way.”
“Have our people then learned how to get power as you do from the use of the principle of the repulsion of gravitation?”
“Indeed they have not,” he answered, “and they are very unlikely ever to find out how to do it unless instructed by us; and that will never be till the Lunarians become lunatics. The new power that has been developed and already brought into considerable use and which will soon become a substitute for all others and endure as long as the earth is habitable is simply sunlight; and the discovery that is to prove by far the most valuable ever made by your race is the direct conversion of its force into electricity, which can as you know be conveyed hundreds of miles and applied to any sort of machinery required. When coal is used to produce electricity, the process is after all an indirect way of utilizing the force of the sun’s rays. Ages ago these rays created the vegetation that afterwards became coal, and in burning the coal now, the force of the sun’s rays consumed in its production is again brought into action in heating the water, that expands into steam that drives the engine, that turns the dynamo, that creates the electric current. It was seen long ago that if some process could be devised by which the force of the sunlight could be consumed in the creation of electricity directly, the suns rays of to-day could be utilized in the production of power instead of using up the coal that was produced by them in former ages. It was discovered in your day that sunlight falling upon the metal selenium is turned in part into electricity. Acting on this hint your scientists experimented with that metal and others, and tried hundreds of combinations and alloys. They have discovered many compounds that possess this property, which is found to depend on the sizes and shapes of the spaces between the molecules of the metal. The impact of the undulations of the ether that give rise to light, striking into the ether confined in these peculiarly shaped spaces impart to it the sort of motion these shapes make it competent to take, which is the new form of motion, electricity. They were largely assisted and guided in their investigations by spectrum analysis. The apparatus for the production of electricity in this way is necessarily of large dimensions presenting large surface to the sun, and as yet is rather expensive, but once made, it lasts forever and produces electricity whenever the sun shines. Improvements are constantly being made that reduce the cost and increase the efficiency. These machines are arranged to turn automatically, a certain face to the sun, revolving on a horizontal plane diurnally and changing their declination vertically to follow the north and south movement of the sun through the seasons. The electricity is transmitted to storage batteries and a surplus thus accumulated during sunshine to be used at night and in cloudy weather or carried off to be used elsewhere. These machines yield especially good results in tropical latitudes and in localities where clear weather predominates, such as southern California, Arizona, northern Mexico, the Sahara desert, Egypt, Arabia, Tartary, Central Australia, etc. In all such countries railroads are operated at nominal expense.
“Stations at intervals transmit the power several hundred miles on either side. As there is practically no limit to this power it has come to be used for the accomplishment of undertakings that were hardly dreamed of before. The irrigation and development of deserts by means of artesian wells and by streams brought from a distance, followed by the construction of roads, settlement and cultivation are being vigorously prosecuted in all parts where the climate is not too cold. Large tracts notably in the Sahara and Gobi deserts and in Arabia and Tartary, have already been made productive and populous. This power can be conveyed to great distances from the point where it is developed, and made to do work in places practically inaccessible to any other form of power. Excavation of canals, railway cuts, tunnels and mines with the transportation of materials for embankments is prosecuted with tremendous energy. Innumerable mines are being pushed far into the bowels of the earth and the interior explored and honeycombed in many directions. This work is however destined to be of vastly more importance in the distant future than at the present. But I think you can now see that with practically unlimited power and unlimited raw materials for the construction of the human race placed in the hands of the race itself your fears that the increase of population will ever press uncomfortably on the means of subsistence are not well founded.”
“Yes I do begin to see that,” said I. “It is all very wonderful. What a career the race has before it! Why it has hardly got out of its cradle yet. What a misfortune that I was not reserved to be born two or three centuries later so I could see some of these future glories!”
“Nay, nay,” he replied, “that is a vain wish. You may be as happy in your own time as you could be in the future. In all the ages of the past, people have been found expressing a poor opinion of their own times, extolling the golden age that was past or the millennium that was to come; and it will be so in the future. If you were to live two centuries hence you would see as many defects and shortcomings, and anticipate as many still future improvements and achievements as you did in your day.”
“Well, I suppose, that must be so; and yet with such an apparently absolute control over the earth it would seem that mankind might make themselves comfortable and contented.”