once."

"You needn't hurry," exclaimed Elsa. "As long as I have no money, I
can't go home!"

Roger looked from Ernest to Elsa, then out the door across the desert to
where the Sun Plant lay in the burning, quivering blue air.

"We'll try it out, Ern," he said. "You know how grateful I am to you
both."

Ernest nodded. "Nobody's using the horses, so I'll drive in and leave
the team at Hackett's. If Dick gets well before I come back he can drive
himself out. Otherwise it will be waiting for me. Elsa, do you think you
could fix up a clean collar and shirt for me?"

"If she can't, I can," offered Charley.

"Take anything you can find of mine," Roger's face was more cheerful
than it had been for days. "I'll get the reports and drawings ready for
you."

So, by the united efforts of the two households, Ernest was made ready
for a flying trip to civilization. He was so happy and excited over the
trip that he really lifted some of the sadness that had hung so heavily
over the ranch house. After his departure, Gustav slept at the ranch, in
order to do the chores while Roger remained at the Plant.

Ever since he had reached the desert Roger had been conducting heat
tests and while he was able under perfectly controlled conditions to
produce higher temperatures than those of the tables he had used for so
many years, his average readings under the absorber glass were less
than he had counted on. And so he was at work on a new type, low
pressure engine, for which his average temperatures would produce ample
heat.

Ernest took little stock in his new idea. "It may take fifty years to
work it out," he had said the day he left for Washington. "Increase your
absorption area and let it go at that. Better men than you have spent
their lives on the low pressure idea and failed."

"I tell you," Roger had insisted, "that with a few changes of this
present engine, I'll produce _the_ low pressure engine of to-day."

"Well, go to it, old man! In the meantime, I'll fetch you some money so
you can buy all the parts needed, and not have to continue your awful
career of mountain brigand. The devilish thing about you inventors is
that you putter so. My God, you drive me crazy! I do honestly believe
that if it weren't for fear of starvation, you'd be puttering here for
ten years."

"You're getting to be nothing better than a common scold, Ern," returned
Roger with a laugh. "I'll be glad to get you out of the camp. Run along
now and do y