1. We investigated the present condition of illuminating means including radioactive luminous paint to the dial navigational instruments to rationalize uisual navigation by exponding look out of range and hastenning adaptability to darkness. 2. In addition to above, we found pattern of rational proportion among length, breadth, and space interval of scale etc., of dial experimentally to make it easy to read, to lesson measuring time of taking bearing etc. 3. Examined actual effect of radio-active luminous paint and showed a procedure to the definitnition of the practical brightness of it.