10. _The colour-blind find more difficulty in comparing colours when different materials are used, than when the coloured objects are all of the same nature._ 11. _Most colour-blind find more difficulty with transmitted than with reflected light._ 12. _The colour-blind have a defective memory for colours._ 13. _Colours may be changed to the normal-sighted whilst leaving them unchanged to the colour-blind._ When three colours of the normal-sighted are included in one of the colour-blind, it is obvious that a change from one colour to another of the three will make no difference to the colour-blind. Also when the spectrum is shortened, the addition or rays corresponding to the shortened portion to another colour will not alter its appearance to the person with the shortened spectrum. For instance, to a person with shortening of the red end of the spectrum, a blue will still remain blue, when so many red rays from the shortened portion have been added to it as to make it appear rose to the normal-sighted. 14. _The colour-blind may have a sense of luminosity similar to that of the normal-sighted._ 15. _The dichromic distinguish between the colours of the normal-sighted, which are included in one of theirs by their relative luminosity and the difference of saturation which is apparent to them._ A test should therefore have the means of presenting colours of different saturation in succession. 16. _Colour-blindness is frequently associated with very high intelligence and exceptional ability._ V. _The Lantern Test._[11]--1. _Description of apparatus._ The lantern contains four discs: three carrying seven coloured glasses, and one with seven modifying glasses. Each disc has a clear aperture. The other mechanical details are: an electric or oil lamp with projecting accessories, a diaphragm for diminishing the size of the light projected, handles for moving the discs and the indicator showing the colour or modifier in use. The diaphragm is graduated in respect to three apertures to represent a 5-1/2-inch railway signal bullseye at 600, 800, and 1000 yards respectively when the test is made at 20 ft. The glasses are as follows:--- _Coloured glasses._ 1. Red (A and B). 2. Yellow. 3. Green. 4. Signal Green. 5. Blue. 6. Purple. _Modifying glasses._ 7. Ground glass. 8. Ribbed glass. 9. Neutral (No. I). 10. " ( " II). 11. " ( " III). 12. " ( " IV). 13. " ( " V). [11] Made by Reiner and Keeler, 9, Vere Street, W.; and Meyrowitz, 1a, Old Bond Street, W. [Illustration: Fig. 3.]