Behind a big boulder on the opposite side of the defile he saw a man's head appear.
Watching for a time, Sanderson made certain the man was not one of his own outfit, and then he shoved the muzzle of his rifle out, laid his cheek against the stock, and covered the partly exposed head of the man behind the boulder.
Sanderson waited long with his cheek caressing the rifle stock, while the man behind the boulder wriggled farther out, exposing himself more and more in his eagerness to gain a more advantageous position.
And presently, without moving his head, Sanderson discovered that it was Williams who was in danger.
Williams had concealed himself behind a jagged rock, which protected him from the bullets fired from across the defile, and from the sides.
But the rock afforded him no protection from the rear, and the man behind the boulder was going to take advantage of his opportunity.
"That's my engineer, mister," he said grimly; "an' I ain't lettin' you make me go to the trouble of sendin' east for another.

You're ready now, eh ?" The man behind the boulder had reached a position that satisfied him.
Sanderson saw him snuggle the stock of his rifle against his shoulder.
Sanderson's rifle cracked viciously.

The man behind the boulder was lying on a slight slope, and when Sanderson's bullet struck him, he gently rolled over and began to slide downward.

He came--a grotesque, limp thing--down the side of the defile, past the engineer, sliding gently until he landed in a queer-looking huddle at the bottom, near the trail.
Sanderson intently examined other rocks and boulders on the opposite side of the defile.

He had paid no attention to Williams' "Good work, Sanderson!" except to grin and assure himself that Williams hadn't "lost his nerve." Presently at an angle that ran obliquely upward from a flat, projecting ledge, behind which another Double A man lay, partly concealed, Sanderson detected movement.
It was only a hat that he saw this time, and a glint of sunlight on the barrel of a rifle.