“We’re trying to give you room,” Tom called.

“I don’t need the room yet.  I won’t run over you, anyway.  Stand out of the brush, I tell you.”

Tom good-humoredly obeyed, Harry moving, too, though starting an instant later.

Prompt as he was, however, Tom Reade was a fraction of a second too late.

Behind them there was a half-whirring, half-clicking sound.

Then Reade felt a stinging sensation in his left leg three or four inches from the heel.

“Look out!” yelled Rutter, more excitedly than before.  “Get away from there!”

Tom ran some distance down the trail.  Then he halted, laughing.

“I wonder what’s on Rut’s mind,” he smiled, as Hazelton joined him.

Jack Rutter came at a gallop, reining up hard as he reached where Tom had stood.

Again that whirring, clicking sound.  Rutter’s pony reared.

“Still, you brute!” commanded Rutter sternly.  Then, without waiting to see whether his mount would stand alone, Rutter leaped from saddle, going forward with his quirt—–­a rawhide riding whip—–­uplifted.

Into the brush from which Tom had stepped Rutter went cautiously, though he did not lose much time about it.

Swish! swish! swish! sounded the quirt, as Rutter laid it on the ground ahead of him.  Then he stepped out.  The pony had drawn back thirty or forty feet and now stood trembling, nostrils distended.

“Is that the way you take your exercise?” Reade demanded.

Rutter, however, came running along the trail, his face white as though from worry.

“Reade,” he demanded, “Did that thing strike you?”

“What thing,” asked Tom in wonderment.

“The rattler that I killed!”

“Rattler?” gasped both cub engineers.

“Yes.  From the distance I thought I saw it strike out at you.  There’s a nest of the reptiles at some point near that brush.  That’s why I warned you to get away from there.  Never stand in brush, in the Rockies, unless you’ve looked before stepping.  Were you struck?”

“I believe something did sting me,” Reade admitted, remembering that smarting sensation in his left leg.

“Which leg was it? demanded Rutter, halting beside the cub.

“Left—–­a little above the ankle,” replied Tom.

“Take off your legging.  I must have a look.  Hazelton, call to one of your chainmen and send him back to make sure of my pony.”

Harry hastened to obey, then came back breathless.  Rutter, in the meantime, had turned up enough of Tom’s left trousers’ leg to bare a spot on the flesh that was red.  There were fang marks in the centre of this reddened surface.

“You got it, boy,” spoke Rutter huskily.  “Now we’ll have to go to work like lightning to save you.”

“How are you going to do it?” asked Tom coolly, though he felt decidedly queer over the startling news.