??? ?? ???? ???? ??? ???? ??? ??? ?? ? ??? ??? ???René Descartes's sketch of how Principal and secondary rainbows are formed, Discours de la Méthode, 1637. Descartes' 1637 treatise, Discourse on Strategy (Discours de la Méthode), further Innovative this rationalization. Being aware of that the dimension of raindrops did not look to affect the ob