The Caldecott prize winner has captured in words and eye-stopping pictures a big day in a small boy's life—the day that he produces without mechanical aid his first, recognizable whistle. Peter tried all day, while fooling around with the things that brighten a city boy's day, to whistle well enough so that his dog, Willie, would respond. He turns in a circle to make himself dizzy, hides in a carton, draws in chalk on the sidewalk and pretends he's his father when he puts on his father's hat. All this is secondary to the effort to whistle and at last he stops Willie in his tracks. The colors here are enough to stop viewers in their tracks. The heat of a city summer is caught in the combination of oranges, yellows and pinks Mr. Keats' technique can only be inadequately described as cutouts in college—bright and beautiful.