Jack went first because, as he said, it was his idea, and he was willing to show his heart was in the right place.

He rolled and lighted a cigarette, wrinkled his eyes shut in a laugh, and strolled nonchalantly out of the stable.
"Keep an eye on the rim-rock, boys," he called back, without turning his head.

A third of the way he went, stopped dead still, and made believe inspect something upon the ground at his feet.
"Ah, go ON!" bawled Wally, his nerves all on edge.
Jack dug his heel into the dust, blew the ashes from his cigarette, and went on slowly to the gate, passed through, and stood well back, out of sight under the trees, to watch.
Wally snorted disdain of any proceeding so spectacular, but he was as he was made, and he could not keep his dare-devil spirit quite in abeyance.
He twitched his hat farther back on his head, stuck his hands deep into his pockets, and walked deliberately out into the open, his neck as stiff as a newly elected politician on parade.

He did not stop, as Jack had done, but he facetiously whistled "Tramp, tramp, tramp, the boys are marching," and he went at a pace which permitted him to finish the tune before he reached the gate.

He joined Jack in the shade, and his face, when he looked back to the stable, was anxious.
"It must be Grant he wants, all right," he muttered, resting one hand on Jack's shoulder and speaking so he could not be overheard from the house.