Whether or not you suspect they seem to be a indication of God's assure, or there is a pot of gold looking ahead to you at their close, rainbows are one of mother nature's most joyful-inducing shows.René Descartes's sketch of how primary and secondary rainbows are formed, Discours de la Méthode, 1637. Descartes' 1637 treatise, Discourse on Approa