on it, but I want to use it if you'll let me. It means a new era in
transcontinental air travel!"

He turned sharply to Fuller. "Fuller, I want you to help Arcot with the
ship to chase the Pirate. You'll get the contract to design the new
airliners. Hang the cost. It'll run into billions--but there will be no
more fuel bills, no oil bills, and the cost of operation will be
negligible. Nothing but the Arcot short wave tubes to buy--and each one
good for twenty-five thousand hours service!"

"You'll get the rights on this if you want them, of course," said Arcot
quietly. "You're maintaining these laboratories for me, and your son
helped me work it out. But if Fuller can move over here tomorrow, it
will help things a lot. Also I'd like to have some of your best
mechanics to make the necessary machines, and to start the power units."

"It's done," Morey snapped.

III

Early the next morning Fuller moved his equipment over to the laboratory
and set up his table for work. There Arcot and Morey joined him, and the
designing of the new machine was started.

"First, let's get some idea of the most advisable shape," Fuller began
methodically. "We'll want it streamlined, of course; roughly speaking, a
cylinder modified to fit the special uses to which it will be put. But
you probably have a general plan in mind, Arcot. Suppose you sketch it
for us."

The big physicist frowned thoughtfully. "Well, we don't know much about
this yet, so we'll have to work it out. You'll have plenty of fun
figuring out strains in this machine, so let's be safe and use a factor
of safety of five. Let's see what we'll need.

"In the first place, our machine must be proof against the Pirate's gas,
for we won't be riding a beam with instruments to guide us safely, if we
pass out. I've thought that over, and I think that the best system is
just what we used in the sample bottles--a vacuum. His gas is stopped by
nothing, so to speak, but there is no substance that will stop it! It
will no doubt penetrate the outer shell, but on reaching the vacuum, it
will tend to stay there, between the inner and outer walls. Here it will
collect, since it will be fighting air pressure in going either in or
out. The pressure inside will force it back, and the pressure outside
will force it in. If we did not pump it out, it would soon build up
pressure enough to penetrate the interior wall. Now, since the stuff can
leak through any material, what kind of a