ABSTRACT
The blue sky above us is the optical layer of the atmosphere, the great lens of the terrestrial globe, its brilliant retina. From ultra-marine, beyond the sea, to ultra-sky, the horizon divides opacity from transparency. . . . But the horizon, the skyline is not only a launch pad. It is also the very first littoral, a vertical littoral, the one which absolutely separates ‘the void’ from ‘the full’. Unremarked invention of the art of painting and of distinguishing a ‘form’ from a ‘background’, the ground line anticipates from afar the maritime shore – the ‘Azure Coast’, that horizontal seaboard that so often causes us to lose sight of the zenithal perspective.1
