desert the region called Xanthus. If I were right,
I ought to hit another grey plain, the Mare Chronium in another couple
of hundred miles, and then another orange desert, Thyle I or II. And so
I did."

"Putz verified our position a week and a half ago!" grumbled the
captain. "Let's get to the point."

"Coming!" remarked Jarvis. "Twenty miles into Thyle--believe it or
not--I crossed a canal!"

"Putz photographed a hundred! Let's hear something new!"

"And did he also see a city?"

"Twenty of 'em, if you call those heaps of mud cities!"

"Well," observed Jarvis, "from here on I'll be telling a few things Putz
didn't see!" He rubbed his tingling nose, and continued. "I knew that I
had sixteen hours of daylight at this season, so eight hours--eight
hundred miles--from here, I decided to turn back. I was still over
Thyle, whether I or II I'm not sure, not more than twenty-five miles
into it. And right there, Putz's pet motor quit!"

"Quit? How?" Putz was solicitous.

"The atomic blast got weak. I started losing altitude right away, and
suddenly there I was with a thump right in the middle of Thyle! Smashed
my nose on the window, too!" He rubbed the injured member ruefully.

"Did you maybe try vashing der combustion chamber mit acid sulphuric?"
inquired Putz. "Sometimes der lead giffs a secondary radiation--"

"Naw!" said Jarvis disgustedly. "I wouldn't try that, of course--not
more than ten times! Besides, the bump flattened the landing gear and
busted off the under-jets. Suppose I got the thing working--what then?
Ten miles with the blast coming right out of the bottom and I'd have
melted the floor from under me!" He rubbed his nose again. "Lucky for me
a pound only weighs seven ounces here, or I'd have been mashed flat!"

"I could have fixed!" ejaculated the engineer. "I bet it vas not
serious."

"Probably not," agreed Jarvis sarcastically. "Only it wouldn't fly.
Nothing serious, but I had my choice of waiting to be picked up or
trying to walk back--eight hundred miles, and perhaps twenty days before
we had to leave! Forty miles a day! Well," he concluded, "I chose to
walk. Just as much chance of being picked up, and it kept me busy."

"We'd have found you," said Harrison.

"No doubt. Anyway, I rigged up a harness from some seat straps, and put
the water tank on my back, took a cartridge belt and revolver, and some
iron rations, and started out."

"Water tank!" exclaimed the little biologist, Leroy. "She