, where she slid along at good speed.

That afternoon Tom busied himself about some wires and a number of
complicated pieces of apparatus which were in one corner of the main
cabin.

"What are you doing now?" asked Mr. Jenks, who had been talking with Mr.
Parker, and showing that scientist some of the manufactured diamonds.

"Getting our wireless apparatus in shape," answered the lad. "I should
have done it before, but I had so much to do that I couldn't get at it.
I'm going to send off some messages. Dad will want to know how we are
doing."

As he worked away, he also made up his mind to send another message, in
care of his father, for there was a receiving station in the Swift home.
And to whom this message was addressed Tom did not say, but we fancy
some of our readers can guess.

Finally, after several hours of work, the wireless was in shape to send
and receive messages. Tom pulled over the lever, and a crackling sound
was heard, as the electricity leaped from the transmitters into space.
Then he clamped the receiver on his ear.

"All ready," he announced. "Has anybody any messages they wish sent?"
For, with the courtesy of a true host he was ready to serve his guests
before he forwarded his own wireless notes.

"Just tell my wife that I'm enjoying myself," requested Mr. Damon.
"Bless my footstool! But this is great! We're off the earth yet,
connected with it."

Mr. Jenks had no one to whom he wanted to send any word, but Mr. Parker
wish to wire to a fellow scientist the result of some observations made
in the upper air.

Tom noted all the messages down, and then, when all was in readiness he
began to call his home station. He knew that either his father or Mr.
Jackson, the engineer, could receive the wireless.

But, no sooner had the young inventor sent off the first few dots and
dashes representing "S. I."--his home station call--than he started and
a look of surprise came over his face.

"They're calling us!" he exclaimed.

"Who is?" asked Mr. Jenks.

"My house--my father. He--he's been trying to get us ever since we
started, but I didn't have the wireless in shape to receive messages.
Oh, I hope it's not too late!"

"Too late! Bless my soul, too late for what?" gasped Mr. Damon, somewhat
alarmed by Tom's manner.

The lad did not answer at once. He was intently listening to a series
of dots and dashes that clicked in the telephone receiver clamped to his
left ear. On his face there was a look