Lord of the Flies Chapters 10 & 11

After reading these two chapters, this book disgusts me. Once they stepped foot on the island they had order and rules and organization. But now that Jack is in charge he is teaching the group of boys to act uncivilized and attack the boys that they were once compains with. Honestly, Im dissappointed that another character has died, and that it was Piggy. Both Piggy and Simon were the characters that tried to harmonize the group and reach their initial group of being rescued. They were killed for that. Jack's uncivilized manor is horrid. I don't understand why Roger would even push a boulder. What made these boys go so crazy, Was it the beast????