These solar motors can be built at no great expense. I was told that ten-horse-power plants would cost about $200 per horse-power, and one-hundred-horse-power plants about $100 per horse-power. This would include the entire plant, with engine and pump complete. When it is considered that the annual rental of electric power is frequently $50 per horse-power, whether it is used or not, it will be seen that the solar motor means a great deal, especially in connection with irrigation enterprises.
The Rear Machinery for Operating the Reflector.
And the time is coming—long-headed inventors saw it many years ago—when some device for the direct utilisation of the sun's heat will be a necessity. The world is now using its coal at a very rapid rate; its wood, for fuel purposes, has already nearly disappeared, so that, within a century or two, new ways of furnishing heat and power must be devised or the human race will perish of cold and hunger. Fortunately there are other sources of power at hand; the waterfalls, the Niagaras, which, converted into electricity, may yet heat our sitting-rooms and cook our dinners. There is also wind-power, now used to a limited extent by means of wind-mills. But greater than either of these sources is the unlimited potentiality of the tides of the sea, which men have sought in vain to harness, and the direct heat of the sun itself. Some time in the future these will be subdued to the purpose of men, perhaps our main dependence for heat and power.
When we come to think of it, the harnessing of the sun is not so very strange. In fact, we have had the sun harnessed since the dawn of man on the earth, only indirectly. Without the sun there would be nothing here—no men, no life. Coal is nothing but stored-up, bottled sunshine. The sunlight of a million years ago produced forests, which, falling, were buried in the earth and changed into coal. So when we put coal in the cook-stove we may truthfully say that we are boiling the kettle with million-year-old sunshine. Similarly there would be no waterfalls for us to chain and convert into electricity, as we have chained Niagara, if the sun did not evaporate the waters of the sea, take it up in clouds, and afterward empty the clouds in rain on the mountain-tops from whence the water tumbles down again to the sea. So no wind would blow without the sun to work changes in the air.
In short, therefore, we have been using the sunlight all these years, hardly knowing it, but not directly. And think of the tremendous amount of heat which comes to the earth from the sun. Every boy has tried using a burning-glass, which, focusing a few inches of the sun's rays, will set fire to paper or cloth.
Professor Langley says that "the heat which the sun, when near the zenith, radiates upon the deck of a steamship would suffice, could it be turned into work without loss, to drive her at a fair rate of speed."
The knowledge of this enormous power going to waste daily and hourly has inspired many inventors to work on the problem of the solar motor. Among the greatest of these was the famous Swedish engineer, John Ericsson, who invented the iron-clad Monitor. He constructed a really workable solar motor, different in construction but similar in principle to the one in California which I have described. In 1876 Ericsson said:
"Upon one square mile, using only one-half of the surface and devoting the rest to buildings, roads, etc., we can drive 64,800 steam-engines, each of 100 horse-power, simply by the heat radiating from the sun. Archimedes, having completed his calculation of the force of a lever, said that he could move the earth. I affirm that the concentration of the heat radiated by the sun would produce a force capable of stopping the earth in its course."