Samenvatting
A series of subjective visibility tests, performed with luminous area, red-light sources of different sizes in artificially generated fog, show that in daytime fog of 50-ft visual range and night-time fog of 100-ft visual range, there wee no appreciable difference in visibility between 2-in. -diameter and 6-in. -diameter sources of equal intensities, In night-time fog of 500-Pt visual range, the larger source was found to be somewhat more visible than the smaller one.