working both engines; but, afraid of
overheating the one they termed their "night engine", they went back to
one motor for the rest of the journey into Para, where they arrived an
hour late. And it was to find bad news awaiting them.

The landing-field official announced that the _Clarion's_ flyers had
left not fifteen minutes before for Freetown, Africa. And upon
investigating the helium valves in the wings of the Sky-Bird, our boys
found to their dismay that fully a third of the pressure was gone,
indicating that an equal quantity of gas had escaped in some manner.

It may be added that there was very little doubt in their minds as to
this manner.

CHAPTER XVII

ACROSS THE ATLANTIC

Our friends looked at each other dismally when they had ascertained the
cause of the Sky-Bird's sluggish flying. Paul and Tom even gave the
craft a tentative push, and found that the loss of her helium had made
her so much heavier to move over the ground that the difference was
manifest at once.

"This looks kind of black for us, fellows," remarked Bob.

"And we've got those scoundrels to thank for it without the shadow of a
doubt," put in Paul, with flashing eyes. "I'd give a year of my life
to get my hands on that Pete Deveaux right now."

"It's lucky they got out ahead of us," added Tom significantly.

"Well, if they were here, and if we thrashed the stuffing out of the
entire bunch, that wouldn't put back our lost helium and former speed,"
said the practical John. "What we've got to do now is to try to remedy
matters."

"Easier said than done, I'm thinking," Tom observed. "We can't get any
more helium here; in fact, not until we get back to Panama. Of course
that will be too late."

"I don't know about that," hinted John.

"What's your remedy?" asked Bob.

"I know," said Paul. "The machine's out of balance now, because they
have let more helium out of one wing than the other, and none at all
out of the fuselage. By letting some out of our body tank, and enough
out of the lightest wing to bring it in equilibrium with its mate, we
can get a perfect balance again, and that ought to give us air
steadiness and more speed."

"Right you are, Buddy," declared John. "Good head! That's my idea
exactly."

"But won't that make us even heavier than we are now?" inquired Bob.

"Sure," responded John, "but balance is the main thing in an airplane,
you know. When we get that, the old girl will act a whole lot be