. Meantime, as
the speed of the boat was rushed up to near the limit of twelve miles,
and they fairly flew over the comparatively smooth gulf, each boy
continued to scan the water, hoping to be the first to report success.

"How long since they passed over, do you think?" asked practical Bluff.

"I should say all of an hour," was Frank's ready response.

"One good thing, there wasn't any sort of a breeze. If it had been
blowing fairly hard, the balloon would be twenty miles away by now, even
if afloat."

"That's a fact Bluff; and as there wasn't an air current of more than a
few miles an hour, one thing seems positive."

"What's that, Frank?" demanded Jerry.

"The balloon must have dropped into the water. If it was still in the air
it could be seen through these powerful glasses miles away."

The others recognized the truth of his words.

"You seem to be heading straight out. Have you any reason for such a
thing?" asked Bluff, seeking information.

"I have. Before we started I carefully noted my bearings. I also made
sure that what little air was stirring came direct from the land, which,
in this case, was almost due east. You can easily see from that which way
the balloon must have drifted up to the minute it dragged in the water."

"Frank, what you say is sound, practical good sense. We must come on some
sign in a short time, if we keep straight on and the conditions remain
the same. I'm only afraid we may be too late," remarked Jerry sadly.

No one else spoke for several minutes as the motor-boat sped merrily
along on her mission of mercy. It was a time of great strain. They hoped
for the best, and yet were conscious of a terrible fear lest the
professor and his assistant might have gone down long ere this.

"The breeze is freshening," remarked Bluff presently.

Frank had noted this, too. It was only natural, for after dawn the air
currents that may have become sluggish during the night were in the
habit of awakening and taking on new life.

He looked back. The land was several miles away by this time. If they
were fated to meet with success in their errand, something must be
showing up very soon now.

Sick at heart with apprehension, Frank handed the glasses over to Jerry,
and was pretending to pay strict attention to the motor. Truth to tell,
his nerves were keyed up to a high tension, as he counted the seconds,
and kept hoping for the best.

Frank had noted one thing that gave him not a little co