13. Arrangement for measuring the luminosities of pigments 83 14. Measurement of the intensity of rays reflected from white and coloured surfaces 88 15. Intensity of rays reflected from vermilion, emerald green, and French ultramarine 92 16. Method of obtaining two patches of identical colour 95 17. Absorption by red, blue, and green glasses 99 18. Light reflected from metallic surfaces 100 19. Intensities of vermilion, carmine, mercuric iodide, and Indian red 101 20. Intensities of gamboge, Indian yellow, cadmium yellow, and yellow ochre 101 21. Intensities of emerald green, chromous oxide, and terre verte 103 22. Intensities of indigo, Antwerp blue, cobalt, and French ultramarine 104 23. Method of obtaining a colour template 104 24. Template of carmine 106 25. Template of luminosity of white light 108 26. Absorption of transmitted and reflected light by Prussian blue and carmine 107 27. Collimator for comparing the intensity of two sources of light 109 28. Spectrum intensities of sunlight, gaslight, and blue sky 109 29. Comparison of sun and sky lights 111 30. Slide with slits to be used in the spectrum 113 31. Screen on which to match gamboge 116 32. Diaphragm in front of prism 128 33. Curve of sensitiveness of silver bromo-iodide 136 34. Curves of colour sensations 139 35. Kœnig's curves of colour sensations 151 36. Maxwell's colour-box 152 37. Maxwell's curves of colour sensations 154 38. Chromatic circle 168 39. Disc to cause alternate opening and closing of two slits 179 40. Disc painted blue and red 181 41. Electro-motor with discs attached 183 42. Method of cutting disc to allow an overlap of a second disc 184 43. Arrangement to find value of gamboge in terms of emerald green and vermilion 188