“You’re right again, dad,” said Cub, with a grim grin of subdued wonder and eagerness.

“I shouldn’t be a bit surprised to find that the Associated Press has chartered a boat and is following us,” declared Mr. Perry.

“Would that be mathematics or geography?” asked Bud.

“It would be imagination,” replied Mr. Perry with a keen smile.  “But, say, Cub, don’t you think you’ve grabbed off enough glory for yourself?  Give your friends a chance to win some honors.”

“Right you are, dad,” returned the boy at the key, rising and removing the phones from his ears.  “Hal, you call half this list and then let Bud call the rest”

It was well for the sake of a distribution of honors that this course was taken, for a thrilling surprise was in store for them in response to the next call.

CHAPTER IX

The Radio Diagram

As good fortune decreed, Hal found Number One in the new list sitting in and listening for anything interesting in the ether.  It required only a few short sentences to acquaint this amateur with the object of the Catwhisker’s search.

“I can tell you just how to find those fellows,” he replied.  “I listened-in to the best line of detective work on that subject you ever heard of.  Sherlock Holmes isn’t in it there.”

“Hooray!” shouted Bud, as he finished jotting down the last sentence.

“There are three amateurs, one in Clayton, N.Y., one in Rockport and one in Gananoque, Ontario, who have radio compasses and they worked together to locate the fellow on the island,” continued the informant with the eagerness of fraternal interest and generosity.  “I will give you their calls—­”

The message was interrupted by a strong spark, which could not be ignored.  Sender Number one stopped sending, and Hal gave ear to the new message.

“I will save you the trouble,” read the dots and dashes evidently addressed to the operator he had just “crowded out,” “I am at Rockport and am one of the three radio compass boys referred to.  I can supply the dope right now.”

Hal threw over the aerial switch and flashed the one word “Shoot!” Then he swung back again and all three boys listened eagerly.

“Have you a good map of the Thousand Island region?” inquired the loop aerial operator.

“Yes,” Hal replied.

“Well, take these directions and then draw the line on the map.  Draw one line from Clayton, N.Y., northeast, 47-1/2 degrees from perpendicular; another from Rockport, Ontario, southeast, 11 degrees from perpendicular; another from Gananoque, southeast, 76 degrees from perpendicular.  The intersection of those lines will indicate the island those messages came from.”

“He was on an island, was he?” asked Hal.

“Sure, or on a boat,” was the reply.  “He could not have been on the mainland.  We were careful and could not have been more than a mile off in our reckoning.  All three of us hit it the same.”