“Another quake!” screamed Mrs. Anderson.  But it was over in a second, and calmness succeeded the incipient panic.

Suddenly, overhead, there sounded a queer crackling noise, a vicious, snapping, as if from some invisible whips.

“Mercy!  What’s that?” cried Mrs. Nestor.

“The wireless,” replied Tom, quietly.  “I am going to send a message for help, off into space.  I hope some one receives it—­and answers,” he added, in a low tone.

The crackling increased.  While they gathered about him, Tom Swift pressed the key, making and breaking the current until he had sent out from Earthquake Island the three letters—­“C.Q.D.”  And he followed them by giving their latitude and longitude.  Over and over again he flashed out this message.

Would it be answered?  Would help come?  If so, from where?  And if so, would it be in time?  These were questions that the castaways asked themselves.  As for Tom, he sat at the key, clicking away, while, overhead, from the wires fastened to the dead tree, flashed out the messages.

CHAPTER XXII

ANXIOUS DAYS

After the first few minutes of watching Tom click out the messages, the little throng of castaways that had gathered about the shack, moved away.  The matter had lost its novelty for them, though, of course, they were vitally interested in the success of Tom’s undertaking.  Only Mr. Damon and Mr. Fenwick remained with the young inventor, for he needed help, occasionally, in operating the dynamo, or in adjusting the gasolene motor.  Mrs. Nestor, who, with Mrs. Anderson, was looking after the primitive housekeeping arrangements, occasionally strolled up the hill to the little shed.

“Any answer yet, Mr. Swift?” she would ask.

“No.” was the reply.  “We can hardly expect any so soon,” and Mrs. Nestor would depart, with a sigh.

Knowing that his supply of gasolene was limited, Tom realized that he could not run the dynamo steadily, and keep flashing the wireless messages into space.  He consulted with his two friends on the subject, and Mr. Damon said: 

“Well, the best plan, I think, would be only to send out the flashes over the wires at times when other wireless operators will be on the lookout, or, rather, listening.  There is no use wasting our fuel.  We can’t get any more here.”

“That’s true,” admitted Tom, “but how can we pick out any certain time, when we can be sure that wireless operators, within a zone of a thousand miles, will be listening to catch clicks which call for help from the unknown?”

“We can’t,” decided Mr. Fenwick.  “The only thing to do is to trust to chance.  If there was only some way so you would not have to be on duty all the while, and could send out messages automatically, it would be good.”

Tom shook his head.  “I have to stay here to adjust the apparatus,” he said.  “It works none too easily as it is, for I didn’t have just what I needed from which to construct this station.  Anyhow, even if I could rig up something to click out ‘C.Q.D.’ automatically, I could hardly arrange to have the answer come that way.  And I want to be here when the answer comes.”