The three legged stool symbolizes the Christian Trinity. Each leg represents something different, the first is God the father. The sceond God the son, and the third the Holy Spirit.
"Selecting the smoothest and roundest stones"-Line 17-18. This is an example of image because it describes the stones with texture.
Tone and Theme
The black dot and black dot are metaphors for death. They are metaphors because out of the black box the black dot is drawn for the lottery. The "winner" who pick the black dot gets "awarded" with death.
"The morning of June 27th was clear and sunny, with the fresh warmth of a full-summer day."-Line 1-2. The tone here is peaceful and calm and it seems like it's going to be a calm book with a happy ending and nothing bad happening.