How does Zane Grey use imagery in Riders of the Purple Sage?

Imagery:

"As a rider guarding the herd he had never thought of the night's wildness and loneliness; as an outcast, now when the full silence set in, and the deep darkness, and trains of radiant stars shone cold and calm, he lay with an ache in his heart. For a year he had lived as a black fox, driven from his kind."

"Wrangle uttered a horrible strangling sound. In swift death action he whirled, and with one last splendid leap he cleared the cason rim. And he whirled downward with the little frog-like shape clinging to his neck!