nd atmosphere, and proposed that they light the great
cavern from end to end and make it an ideal place where they could live
as it suited them.

"I see that you guess the end. My ancestor was a great student of the
sciences and had already thought of putting electricity to practical
use. You are surprised? Yes, it has been applied to our purposes for two
hundred years, while your people have understood its use such a short
time."

"Great heavens!" exclaimed the Englishman. "I see it all; the sun is an
electric one!"

"Yes."

"And it runs mechanically over its great course as regularly as
clock-work."

"More accurately, I assure you, but there probably never was a greater
mathematical problem than they solved in deciding on the size the sun
should be and amount of light necessary to fill up all the recesses of
the great vacancy. It was all very crude at the start; for years a great
electric light was simply suspended in the centre of the cavern's roof
and the light did not vary in color. A son of the first king suggested
the plan of giving the sun diurnal movement and the changing light. The
moon and stars were a later development. They found, too, that the light
could not be made to reach certain recesses in the cavern where the roof
approached the earth, so they finally built a great wall to keep the
inhabitants within proscribed boundaries, and to prevent them from
understanding the machinery of the heavens."

"Wonderful!" exclaimed Thorndyke. "But the temperature of the
atmosphere, how does that happen to be so delightful and beneficial?"

"I believe they do not themselves thoroughly comprehend that. The heat
comes from the internal fires, and the fresh air from without in some
mysterious way. At first, in a few places, the heat was too severe, but
the scientific men among the first settlers obviated this difficulty by
closing up the hottest of the fissures and opening others in the cooler
parts of the cavern."

"And the people, where did they come from?"

"From all parts of the earth. We had agents outside who selected
such men and women that were willing to come, and who filled all the
requirements, mentally and physically."

"But why do they desire to live here instead of out in the world, when
they have all the wealth that they need to assure every advantage."

"They dread death, and it is undoubtedly true that life is prolonged
here; our medical men declare that the longevity of every generation i