As we’d roll along, we’d sing three-and four-part harmony, with Mother and Dad joining in as soprano and bass. “Bobolink Swinging on the Bow,” “Love’s Old Sweet Song,” “Our Highland Goat,” “I’ve Been Working on the Railroad.” “What do only children do with themselves?” we’d think. Dad would lean back against the seat and cock his hat on the side of his head. Mother would snuggle up against him as if she were cold. The babies were asleep now. Sometimes Mother turned around between songs and said to us: “Right now is the happiest time in the world.” And perhaps it was.