Nid and Nod by Ralph Henry Barbour — Read

There was an instant of incredulous horror on the cliff top. Then Polly's smothered gasp broke the silence, and the two boys were on their feet. Short of the edge, Ned faltered for a moment, sick and trembling, and it was Bob who crouched on hands and knees and looked first down the steeply sloping face of rock. Beside him the earth was still trickling where Laurie's unwary foot had broken off an overhanging crust.

For a second Bob's gaze, fearfully searching the rocky débris far below, saw nothing. Then came a sharp cry of relief from Ned, who had now dropped beside him, and at the same moment Bob's gaze, retraveling the face of rock, fell on Laurie.