The cultural history of clouds seemed to be shaped by amateurs — the likes of Luke Howard and the Honorable Ralph Abercromby — each of whom projected the ethos of his particular era onto those billowing blank slates in the troposphere. Gavin Pretor-Pinney was our era’s. On today’s Sunday Read, the story of the Cloud Appreciation Society and how Mr. Pretor-Pinney, backed with good will, challenged the cloud authorities.