Bloom of Cactus by Robert Ames Bennet — Read

Before the falling Apache smashed down upon the cliff foot the man who had last climbed the long ladder made an upward rush. He was within half a dozen rungs of the top when a large round object rolled out of the doorway. With the quickness of a puma he swung off to one side.

The big missile grazed past the dodger. Three or four yards farther down it crashed upon the ladder. All the mid section of the wobbly structure was shattered to flinders. The lower part slithered sideways along the cliff face, the upper part and the two climbers plunged downward.