I should like to recommend to [the reader]…that he gaze long and philosophically one afternoon in spring at the azure of the sky, on a day wholly without clouds and preferably in a Mediterranean country. Then he will observe that this azure is composed, as it were, of a precious substance which eludes his rational faculties, for at the same time that it will apear to him to be made up of an infinitely smooth and hard substance, like an agate sphere, this homogeneity, so opaque and materially corporeal, will seem luminous and as if composed of transparency and of spirituality itself. And in this the sensations just described will be in accord with physics, since the hardness and the violence, so to speak, of such an azure are constituted of nothing but infinite layers of superposed transparent air. Exactly the same thing is true of a beautiful pictorial matter. [A color existing as a beautiful and transcendant pictorial matter]…is constituted and formed, like the very azure of the sky which serves as our example, by a succession of subtle, quasi-spiritual and infinitely fine successive layers, as transparent as possible, and for the obtaining of which the magic of media intervenes.