"I'm sure I can't tell you," replied Mr. Perry. "But you have a dandy field to work on. All you need is a little imagination; then begin to do a little head-work, and before you know it you'll have a lead to work on. And let me add something more. There are two things in this world, which, working together, can knock a mystery into a cocked hat more successfully than anything else in the world that I know of."
"I bet I know what they are," Cub volunteered, eagerly.
"Mathematics and imagination," almost shouted Hal in a wild scramble of mind to beat Cub with the answer.
The latter cast a wrathful glance at the saucy youth who had broken in ahead of him.
"Tee-hee!" laughed Bud with fitting imitation of Hal's characteristic vocal merriment.
As for Tee-hee, that worthy individual preserved his dignity for the nonce.
"Well," laughed Mr. Perry; "You've hit the nail on the head, but I venture to say you can't explain why mathematics and imagination can put a mystery to rout."
Hal confessed he was unable to explain.
"It's too much highbrow for me," he said. "And I bet it's too much highbrow for Cub."
The latter said nothing. Evidently he was thinking hard. He leaned back in his camp chair and hoisted his feet upon the rail again.