The full quote for this episode is:
'Roger gathered a handful of stones and began to throw them. Yet there was a space round Henry, perhaps six yards in diameter, into which he dare not throw. Here, invisible yet strong, was the taboo of the old life. Round the squatting child was the protection of parents and school and policemen and the law. Roger’s arm was conditioned by a civilization that knew nothing of him and was in ruins.'
As the first person to answer stated, it is in the first half of Chapter 4, 'Painted Faces and Long Hair'. I would imagine that it would also be useful to know what the significance of the quotation means. Roger is one of the lesser characters within the novel, a boy who is easily influenced by others and has clearly until this point been relatively well brought up. It is clear that he would like to bully the other boy if he were able but he has been 'conditioned by a civilization', that of Britain, where he grew up, to behave in a kind fashion towards other boys. However, even though there is a war raging and he is now far removed from his family as a result of the plane crash, his upbringing still has a residual effect upon him which is 'invisible yet strong' - his moral education has rendered him incapable at this point of exploiting the weakness of the younger Henry.
The importance of this scene, however, remains in the fact that this scene occurs just before Jack paints his face and that of the other 'hunters' on the island, one of the telling signs of their descent into atavism (savagery) and the dissolving of the parental influence that had so far kept them broadly under control. It is telling that in a few chapters, savagery had so fully controlled the boys' actions that one cannot imagine Roger leaving the space between Henry and the stones and would, perhaps, have been more willing to throw the stones at him. Thus, the scene has been carefully constructed by Golding as a marker of the lingering influence of parental influence on the boys just at the point where we are given a good example of this influence waning.
This quote can be found in Chapter 4, on page 62, of the novel, Lord of the Flies. This scene takes place earlier in the novel and involves Roger throwing stones in proximity to Henry, who is playing on the beach. Roger is careful not to hit Henry with any stones because he has been conditioned by society not to inflict harm upon others. The "invisible six-yard diameter circle" surrounding Henry is a remnant of civility ingrained into Roger by his parents, teachers, and other adult influences. Throughout the novel, Golding depicts the moral degradation of individual characters like Roger. In this scene, Roger is able to maintain control of his emotions and respects Henry's well-being by not aiming directly at him. Later on in the novel, Roger shows no restraint and harms the other boys on the island. Golding suggests that without consistent supervision, rules, and consequences, individuals revert to their animal instincts. Roger's moral upbringing is eventually forgotten as he descends into savagery, becoming the most feared sadist of all the boys.
It's on page 64 of my edition, a few pages into Chapter 4: "Painted Faces and Long Hair".
on mii version its on pagee 42