ephone receiver which the operator at
the receiving station wears on his ear. He hears the code of clicks,
and translates them into letters, the letters into words and the
words into sentences. That is how wireless messages are sent."

"And do you propose to send some that way?" asked Mrs. Anderson.

"I do," replied Tom, with a smile.

"Where to?" Mrs. Nestor wanted to know.

"That's what I can't tell," was Tom's reply. "I will have to project
them off into space, and trust to chance that some listening
wireless operator will 'pick them up,' as they call it, and send us
aid."

"But are wireless operators always listening?" asked Mr. Nestor.

"Somewhere, some of them are--I hope," was Tom's quiet answer. "As I
said, we will have to trust much to chance. But other people have
been saved by sending messages off into space; and why not we?
Sinking steamers have had their passengers taken off when the
operator called for help, merely by sending a message into space."

"But how can we tell them where to come for us--on this unknown
island?" inquired Mrs. Anderson.

"I fancy Captain Mentor can supply our longitude and latitude,"
answered Tom. "I will give that with every message I send out, and
help may come--some day."

"It can't come any too quick for me!" declared Mr. Damon. "Bless my
door knob, but my wife must be worrying about my absence!"

"What message for help will you send?" Captain Mentor wanted to
know.

"I am going to use the old call for aid," was the reply of the young
inventor. "I shall flash into space the three letters 'C.Q.D.' They
stand for 'Come Quick--Danger.' A new code call has been instituted
for them, but I am going to rely on the old one, as, in this part of
the world, the new one may not be so well understood. Then I will
follow that by giving our position in the ocean, as nearly as
Captain Mentor can figure it out. I will repeat this call at
intervals until we get help--"

"Or until the island sinks," added the scientist, grimly.

"Here! Don't mention that any more," ordered Mr. Hosbrook. "It's
getting on my nerves! We may be rescued before that awful calamity
overtakes us."

"I don't believe so," was Mr. Parker's reply, and he actually seemed
to derive pleasure from his gloomy prophecy.

"It's lucky you understand wireless telegraphy, Tom Swift," said Mr.
Nestor admiringly, and the other joined in praising the young
inventor, until, blushing, he hurried off to make some adjustm