What caused Roger to contemplate "the possibilities of irrisestible authority"?

At Castle Rock, Roger is attempting to gain entry to Jack's camp. Robert, already inside, makes Roger announce himself before he can enter-one of Jack's new rules. When Roger enters, Robert shows him a new feature of Jack's camp: the boys have rigged a log so that they can easily trigger a rock to tumble down and crush whatever is below it. Roger appears disturbed by this, and Robert changes the subject, telling him that Jack had a boy named Wilfred tied up for no apparent reason. Roger considers the implications of Jack's "irresponsible authority" and makes his way back down to the caves and the other boys in Jack's tribe.