had come up with calculations that said this poison beam had to be something like a radar beam or a laser beam or something like that.  And the American scientists were right out there in front, along with guys from England and France and Italy and Germany and even Russia.  All the big brains of the world were workin’ on it!  Those Martians were gonna wish they’d come visitin’ polite instead of barging in like they owned the world!  They’d be lucky if they wound up ownin’ Mars!

Lockley pressed for details about the scientists’ results.  He didn’t expect to get them, but the driver cheerfully obliged.

Radio, said the driver largely, worked by making waves like those on a pond.  They spread out and reached places where there were instruments to detect them, and that was that.  Radar made the same kind of waves, only smaller, which bounced back to where there was an instrument to detect them.  These were ripple waves.

Lockley interpreted the term to mean sine waves, rounded at top and trough.  It was a perfectly good word to express the meaning intended.

These were natural kindsa waves, pursued the driver.  Lightning made them.  Static was them, and sparks from running motors and blown fuses.  Waves like that were generated whenever an electric circuit was made or broken besides their occurrence from purely natural causes.

“We can’t feel ’em,” said the driver expansively.  “We’re used to waves like that.  Animals couldn’t do anything about ’em and didn’t need to before there was men.  So when we come along, we couldn’t notice ’em any more than we notice air pressure on our skin.  We’re used to it!  But these scientists say there’s waves that ain’t natural.  They ain’t like ripples.  They’re like storm waves with foam on ’em.  And that’s the kind of waves we can notice.  Like storm waves with sharp edges.  We can notice them because they do things to us!  These Martians make ’em do things.  But now we know what kinda waves they are, we’re gonna mess them up!  And I’m savin’ up a special kick for one o’ those Martians when they’re licked just as soon as I can find out which end of him is which an’ suited to that kinda attention!”

Lockley found himself suspicious and was annoyed.  Jill was safe now.  This driver was well-informed, but probably everybody was well-informed now.  They had reason to become so!

The truck trundled through the night.  High overhead, a squadron of planes arrived to take its place in the ever-moving patrol around the Park.  Another squadron, relieved, went away to the southwest.  There was a deep-toned, faraway roaring from the engines aloft.  All the sky behind the trailer seemed to mutter continuously.  But the roof of stars ahead was silent.

Lockley stayed tense and was weary of his tenseness, Jill was safe.  He tried to reason his uneasiness away.  The cab of the truck wobbled and swayed.  The feel of the vehicle was entirely unlike the feel of a passenger car.  It felt tail-heavy.  The driver had ceased to talk.  He seemed to be musing as he drove.  He’d asked about the invaders but seemed almost indifferent to any adventures Jill and Lockley might have had on their way out.  He didn’t ask what they’d done for food.  He was thinking of something else.