ghtfall before the huge tanks had again been
filled. Even then there was a bit more room for the atomic hydrogen that
was simultaneously formed, although twice as much hydrogen as oxygen was
produced. Its task completed, the _Solarite_ rose again and sped toward
the distant city.

A soft red glow filled the sky now, for even through the miles of clouds
the intense sun was able to force some direct rays, and all the city was
lighted with that warm radiance. The floodlights had not yet been turned
on, but the great buildings looming high in the ruddy light were
wonderfully impressive, the effect being heightened by the planned
construction, for there were no individual spires, only a single mass
that grew from the ground to tower high in the air, like some man-made
mountain.

Back at the Capital the _Solarite_ again settled into the broad avenue
that had been cut off to traffic now, and allotted to it as its resting
place. Tonlos met them shortly after they had settled into place, and
with him were five men, each carrying two large bottles.

"Ah-co," as Tonlos pronounced the Terrestrian name, "we have not been
able to make very much of the materials needed for your gas, but before
we made any very great amount, we tried it out on an animal, whose blood
structure is the same as ours, and found it had the same effect, but
that in our case the iodide of potassium is not as effective in
awakening the victim as is the sorlus. I do not know whether you have
tried that on Terrestrial animals or not. Luckily sorlus is the most
plentiful of the halogen groups; we have far more of it than of
chlorine, bromine or iodine."

"Sorlus? I do not know of it--it must be one of the other elements that
we do not have on Earth. What are its properties?"

"It, too, is much like iodine, but heavier. It is a black solid melting
at 570 degrees; it is a metallic looking element, will conduct
electricity somewhat, oxidizes in air to form an acidic oxide, and forms
strong oxygen acids. It is far less active than iodine, except toward
oxygen. It is very slightly soluble in water. It does not react readily
with hydrogen, and the acid where formed is not as strong as HI."

"I have seen so many new things here, I wonder if it may not be the
element that precedes niton. Is it heavier than that?"

"No," replied Tonlos; "it is just lighter than that element you call
niton. I think you have none of it."

"Then," said Arcot, "it must be the next mem