glad that she had cautioned
him thus--and in such tones as she had used. For Mary Nestor was a girl
that any young chap would have been glad to have manifest an interest in
him.

"Well, I guess I'll have to say good-by," spoke Tom, at length. "We
expect to start in a couple of days, and I may not get another chance to
see you."

"Oh, I--I hope you come back safely," faltered Mary, and then she held
out her hand, and Tom--well, it's none of our affair what Tom did
after that, except to say that he hurried out, fairly jumped into his
monoplane, and completed the trip home.

As the Red Cloud has been fully described in the volume entitled "Tom
Swift and His Airship," we will not go into details about it now.
Sufficient to say that it was a combination of a biplane and dirigible
balloon. It could be used either as one or the other, and the gas-bag
feature was of value when the wind was too great to allow the use of the
planes, or when the motive power, for some reason stopped. In that event
the airship could remain suspended far above the clouds if necessary.
There was provision for manufacturing the gas on board.

The Red Cloud was fitted up to accommodate about ten persons, though it
was seldom that this number was carried. Two persons could successfully
operate the machinery. There were sleeping berths, and in the main cabin
a sitting-room, a dining-room, and a kitchen. There was also the motor
compartment, and a steering tower, from which the engines could be
controlled.

It was in this craft that the seekers after the diamond makers proposed
undertaking the trip. Mr. Damon came on from his home in Waterfield
about two days before the date set to leave, and Mr. Jenks, had, three
days before this, taken up his abode at the Swift home. Mr. Parker, as
has been stated, was already there, and he had put in his time making
a number of scientific observations, though he had made no more
predictions.

Nothing more had been seen of the mysterious man who had warned Tom,
and the young inventor and Mr. Jenks began to hope that they had thrown
their enemies off the track.

"Though I don't imagine they'll give up altogether," said Mr. Jenks.
"They're too desperate for that. We'll have trouble with them yet."

"Well, it can't be helped," decided Tom. "We'll try and be ready for it,
when it comes," and then, dismissing the matter from his mind, he busied
himself about the airship.

The food and supplies had all been put ab