about three o'clock
They decided that the grassy valley was almost uninfested by things dangerous . They became reckless sometimes , and would work in the pit together . As a rule , though , they were cautious -- this was an inherent and necessary quality of a cave being -- and it was well for them that it was so , for when an emergency came only one of them was in the pit , while the other was aloft in the lookout and alert . It was about three o'clock one afternoon when Ab , whose turn it chanced to be , was working valiantly in the pit , while Oak , all eyes , was perched aloft . Suddenly there came from the treetop a yell which was no boyish expression of exuberance of spirits . It was something which made Ab leap from the excavation as he heard it and reach the side of Oak as the latter came literally tumbling down the bole of the tree of watching . `` Run ! ''