Which detail in these lines from Stephen Crane's The Red Badge of Courage creates an ominous mood? "When another night came the columns, changed to purple streaks, filed across two pontoon bridges. A glaring fire wine tinted the waters of the
river. Its rays, shining upon the moving masses of troops, brought forth here and there sudden gleams of silver or gold. Upon the other shore a
dark and mysterious range of hills was curved against the sky. The insect voices of the night sang solemnly."