“Look here, old man,” said Bob, anxiously, “you want to quit thinking about that or you’ll be sick.”

“Sick?” Frank tried to force a laugh. “I’m the healthiest invalid ever you saw.”

“No, Frank, I mean it. Put that thought out of your mind, or you will be sick. Why—”laying a hand on his brow—“you’ve got a fever right now.”

Jack was worried, too.

“Great guns, Frank, you must take Bob’s advice. What if you came down sick? We’d be in a pretty fix.”

“Oh, you fellows make me tired,” said Frank, irritatedly. “I’m all right.”

But Bob’s worry was not routed. He took his chum by an arm and started marching him toward camp.

“I’m going to give you a dose of calomel and make you lie down,” he said. “Come on.”

“Calomel? Have a heart.”

“Yes, calomel,” said Bob, firmly. “That’s what you need, that and a nap.”