Stacy spurred his pony close up to the leaders.  The lad’s face was solemn, but it shone like an Eskimo’s after a full meal of blubber.  Ned Rector was next ahead of the fat boy.  Chunky pretended not to see Rector.  Riding close up to him, the fat boy softly gave his rattlesnake imitation.

Ned Rector made a high dive, landing head first in a thicket of mesquite brush, while his pony was left kicking and bucking on the trail.  Stacy was having more trouble with his own pony.

“Whoa, there, you fool!  Whoa!  What’s got into this beastly pinto?” howled the fat boy.

“That’s what I’d like to know too,” snapped the captain, wheeling his horse, giving the fat boy a quick, sharp glance.

Ned, having picked himself out of the mesquite bush, was limping back.

“You hit him, Stacy Brown!” shouted Rector.

“I never touched him.  What’s the matter with you?” protested Chunky indignantly.

“No quarreling, boys,” warned the professor.

“Well, he doesn’t want to be poking my pony!”

“Well, he doesn’t want to be accusing me of poking his old bundle of bones.”

“Pretty lively critter for a bundle of bones, I should say,” answered the captain grimly.

“Nobody trailing,” announced the scouts returning a few minutes later.  The captain may have had a suspicion, but if so he kept it to himself, making no reply to the report of his two scouts.

For reasons best known to himself Stacy did not give his rattlesnake imitation again.  But every little while a broad grin would grow on his countenance, which the fat boy would suppress as quickly as possible.

“This is too good a thing to be nipped in the bud,” he muttered.  “No, sir, I don’t give my secrets away yet awhile.  Mebby I never shall.”

Stacy well knew that swift punishment would be meted out to him if the others caught him at his new trick, so the fat boy kept silent, looking the picture of innocence.

CHAPTER XVIII

ONE HISS TOO MANY

The Ten-Mile cross trail was made about half past one o’clock in the afternoon.  Walter Perkins entered the camp on his head, Tad Butler hanging to the mane of his bucking pony, both feet out of the stirrups, Stacy Brown making desperate efforts to quiet his own mount.

The ponies had heard the soft hiss of a rattlesnake, but the ears of Rangers and Pony Riders had failed to catch the sound.  Perhaps it was the yell that the fat boy had uttered instantly after giving the imitation that had too suddenly attracted the attention of the party.

“What’s the matter with those fool cayuses?” shouted Dippy Orell.  “What—–­”

Dippy did not finish his remark.  He landed on his back thoroughly shaken down.  He was up with a roar, starting for the pony with blood in his eye.