y again up through the ship, up through the
room of the tremendous cylinder coil, and then into the power room. Now
the machines were quiet, for the motors were no longer working.

"Arcot, you didn't shut off the biggest machine of all down there. How
come?"

"I couldn't, Wade. It has no shut-off control, and if it did have, I
wouldn't use it. I will tell you why when we get back to the
_Solarite_."

At last they left the mighty machine; walked once more across its broad
metal top. Here and there they now saw the ends of those quartz
cylinders. Once more they entered the _Solarite_, through the air lock,
and took off the cumbersome insulating suits.

As quickly as possible Arcot outlined to the two who had stayed with the
_Solarite_, the things they had seen, and the layout of the great ship.

"I think I can understand the secret of all that power, and it's not so
different from the _Solarite_, at that. It, too, draws its power from
the sun, though in a different way, and it stores it within itself,
which the _Solarite_ does not try to do.

"Light of course, is energy, and therefore, has mass. It exerts
pressure, the impact of its moving units of energy--photons. We have
electrons and protons of matter, and photons of light. Now we know that
the mass of protons and electrons will attract other protons and
electrons, and hold them near--as in a stone, or in a solar system. The
new idea here is that the photons will attract each other ever more and
more powerfully, the closer they get. The Kaxorians have developed a
method of getting them so close together, that they will, for a while at
least, hold themselves there, and with a little 'pressure', will stay
there indefinitely.

"In that huge coil and cylinder we found there we saw the main power
storage tank. That was full of gaseous light-energy held together by its
own attraction, plus a little help of the generator!"

"A little help?" Wade exclaimed. "Quite a little! I'll bet that thing
had a million horsepower in its motor!"

"Yes--but I'll bet they have nearly fifty pounds of light condensed
there--so why worry about a little thing like a million horsepower? They
have plenty more where that comes from.

"I think they go up above the clouds in some way and collect the sun's
energy. Remember that Venus gets twice as much as Earth. They focus it
on those tubes on the roof there, and they, like all quartz tubes,
conduct the light down into the condensers where