Tough problems have been put to the lighting engineers of England in the effort to brighten the blackout on the ground without brightening it for the enemy bomber overhead. A number of eminent men have given time voluntarily to designing “light locks,” study of luminous paints, planning and testing traffic lights and the illumination of railroad yards and docks where work must go on all night, regardless of air-raid hazards. “Artificial starlight” on the streets enables pedestrians to avoid obstacles, but is invisible from the sky. Research into human vision, one project assigned to a subcommittee of the Iluminating Engineering Society, has developéd - that the human eye does not function in darkness as in normal light; in the blackout people develop a “blind spot” at the center of the pupil and see “around the edges.” This means that small objects are not seen, and the air-raid signs must be of a certain minimum size if they are to be of any value in the dark. The blackout entrances to stores are scientifically light-trapped to prevent any escape of light from indoors; a group of English engineers cooperated with a photographic firm to design these light locks. Light-trapped windows have also been developed, and ventilators that circulate air without letting out light to attract an invading airman. The British intend that a dark exterior shall not mean a dim interior.