The author has, ever since 1950, been in the comparative study of fluorescent lamps and incandescent lamps as artificial light-sources by making quantitative and qualitative experiments to prove which is superior from the viewpoint of eye-hygiene and illumination engineering. This time, the author conducted comparative experiments with both types of light-sources in relation to speed of vision with fixed test types, and discernible velocity with moving objects, coming to the following conclusion. A. Fixed Test Types (1) Of all types of light-sources, irrespective of white or colored, time of exposure drastically lessens for the range from 1 H. Lux to 30 H. Lux, and the minimum is reached at about 50 H. Lux. Then gradual decrease in time of exposure continues up until 100 H. Lux. The speed of vision is proportional to logarithm of intensity of illumination. (2) White light is usually superior in speed of vision to any colored light, namely, de luxe daylight fluorescent lamp is best, and then daylight fluorescent lamp and white fluorescent lamp come next slight differences. Then the incandescent lamp, blue-white fluorescent lamp, green fluorescent lamp, and pink fluorescent lamp follow in the order. (3) The rate of the increase in speed of vision to the increase in intensity of illumination is greater in low intensity of illumination, and it grows smaller as intensity of illumnation rises up. B. Moving Object (4) Discernible velocity varies even with the same regularly spaced black and white stripe-patterns in accordance with the angle to face the direction of movement. Discernible velocity is at the minimum in case of the angle of ±45°, and as getting farther off from this angle, it grows the greater. (5) The broader the space is between the black and white stripes, the greater will be the discernible velocity. (6) In case the size of test type remains unchanged, discernible velocity suddenly grows greater until the intensity of illumination on the surface of test type is as large as 3050 H. Lux, and thence up to 500 H. Lux, it continues to increase but gradually. Discernible velocity is proportional. to logarithm of intensity of illumination. (7) In case intensity of illumination is constant, discernible velocity gets heightened, as the test type grows larger in area. A lineal relation is established between the two factors. (8) In case the bright and dark faces of the moving object continue to alternate, the illumination by fluorescent lamps is found inferior to that of incandescent lamps in low intensity of illumination up to 100 H. Lux. In cases other than the above, no significant difference is noticed between the two light-sources, irrespective of moving object or intensity of illumination.