“What is it?” they asked, almost involuntarily sinking their voices into a whisper.
“It is the mystery of Lost River Canyon,” replied Bob, solemnly. “Here’s Mr. Evans. Ask him.”
The boys turned about in their saddles, and saw that the wagon had come up and stopped close behind. They knew that both of its occupants had been listening to the strange sound that had just died away. Mr. Evans looked indifferent, but Uncle Bob was visibly affected.
“What is it, Mr. Evans? and where does it come from?” asked George, as he rode up beside the wagon.
“It undoubtedly has its origin somewhere in the mountains,” was the reply; “but just where it comes from, and what causes it, are questions that no one has yet been able to answer.”
“What is your theory?” asked George.
“I have none.”
“Why doesn’t somebody go into the mountains and solve the mystery?”
“Haven’t I told you over and over again that the attempt has often been made, and that nothing ever came of it?” said Bob. “I gave you to understand that there was a mystery connected with these mountains, and now you know as much about it as I do.”
“Couldn’t one follow up the sound, and so find its source?” inquired Uncle Bob.