"If we start sinking a shaft into the earth, the heat increases rapidly as we go down—more quickly in some parts of the world than others. On an average, the temperature rises about one degree Fahrenheit each 100 feet of depth. We found it economic, therefore, to use the earth's own heat to heat our farms.
"By means of high speed drills, we can cut a three-foot shaft 3,000 feet deep in the earth in less than a month. We go down until we strike a temperature around 100 to 120 degrees Fahrenheit. Then we lower steel tanks into the cavity and run pipes up to the surface. The tanks are filled with water and two larger pipes run from each tank into the circulating system of pipes, around the lower walls throughout the length and breadth of the farms. The shafts are then closed at the top and we have a circulating system that is both cheap and efficient. The hot water continually rises into the pipes and circulates. As it cools, it flows down again into the tanks, where it is reheated and rises again. Thus the temperature of our farms is uniform all the year around and plant growth is as rapid during the night as during the day.
"Heat alone, however, is not sufficient. We should still get only a normal growth. We wanted five crops a year. I put my research forces to work studying fertilizers. While the old nitrogen fertilizers were excellent, they were not suitable for high pressure, high speed growing methods. We evolved chemicals which were both cheap and easy to apply. We found that small quantities of Termidon, when mixed with water and sprayed over the field by overhead sprayers, which you will see running along the ceiling, would accelerate the growth of the crops enormously.
"This liquid Termidon is sprayed over the entire length and breadth of the field before planting time, so that the soil becomes well soaked. The Termidon immediately turns the soil into a rich, dark strata, the best soil for potatoes, wheat, or corn. No other fertilizer need be used, the Termidon, applied after every growth, giving the soil all the vitality necessary."
They were now in the field, when suddenly Alice asked:
"What is the peculiar tingling in the soles of my feet, I feel as we walk along? You are using some electrical vibrations, I suppose."
"You guessed correctly," Ralph replied. "With all our artifice the speed of the plant growth had not been accelerated sufficiently. I therefore insulated the inside hothouse from the ground. The inside hothouse rests upon glass blocks, and is electrified by high frequency currents. The entire area is sprayed day and night with a high frequency current, in the use of which we found was the real secret of driving plant growth ahead at enormous speed. The theory of course is nothing new, having been known for centuries. What is new, however, is the way it is done. It makes all the difference in the world if the current density is too high or too low, if it is direct or alternating current, and many other details. I found that the quickest way to accelerate plant growth by electricity was to send the current from the growing plant toward the ceiling, and the current must be direct, pulsating, but not alternating."
Ralph asked for a discharge pole from one of the attendants. It was a metal pole about seven and a half feet high. In the middle it had a long glass handle which Ralph grasped. He then set the pole vertically so that its top was about six inches from the glass ceiling. A roar of fine sparks leaped from the steel frame of the ceiling to the top of the pole.
"See," said Ralph, "there is the current we use in accelerating the growth of our plants."
Removing the pole, Ralph continued: "The electrical current density per square foot is not very high and the wheat does not get a very great amount of electricity during the twenty-four hours. The continuance of the force applied is what counts."