How does Thomas Hoving use imagery in Andrew Wyeth: Autobiography?

Imagery:

"Why do I call it Night Sleeper? Because that patch of light reminded me of the sleeper trains I used to take to Maine when I was a child. This thing just grew. I had this enormous panel and kept on and on until it was used up. I didn't want a half thought; I wanted a whole one. People think it's half Pennsylvania, half Maine."