granite boulder lying against it on the outside--or what had been a
boulder, though it had been shattered by the impact.

"Say--that's some building material!" Arcot indicated the transparent
sheet. "Just look at that granite rock--smashed into sand! Yet the
window isn't even scratched! Look how the frame that held it is
torn--just torn, not broken. I wonder if we can tear it loose
altogether?" He stepped forward, raising his pistol. There was a thud as
his metal bar crashed down when the ray was shut off. Then, as the
others got out of the way, he stepped toward the window and directed his
beam toward it. Gradually he increased the power, till suddenly there
was a rending crash, and they saw only a leaping column of earth and
sand and broken granite flying up through the hole in the steel shell.
There was a sudden violent crash, then a moment later a second equally
violent crash as the window, having flown up to the ceiling, came
thumping back to the floor.

After the dust had settled they came forward, looking for the window.
They found it, somewhat buried by the rubbish, lying off to one side.
Arcot bent down to tilt it and sweep off the dirt; he grasped it with
one hand, and pulled. The window remained where it was. He grasped it
with both hands and pulled harder. The window remained where it was.

"Uh--say, lend a hand will you, Wade." Together the two men pulled, but
without results. That window was about three feet by two feet by one
inch, making the total volume about one-half a cubic foot, but it
certainly was heavy. They could not begin to move it. An equal volume of
lead would have weighed about four hundred pounds, but this was
decidedly more than four hundred pounds. Indeed, the combined strength
of the three men did not do more than rock it.

"Well--it certainly is no kind of matter we know of!" observed Morey.
"Osmium, the heaviest known metal, has a density of twenty-two and a
half, which would weigh about 730 pounds. I think we could lift that, so
this is heavier than anything we know. At least that's proof of a new
system. Between Venus and Earth we have found every element that occurs
in the sun. These people must have come from another star!"

"Either that," returned Arcot, "or proof of an amazing degree of
technological advancement. It's only a guess, of course--but I have an
idea where this kind of matter exists in the solar system. I think you
have already seen it--in the gaseous state. You r