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II4 Image, virtual, formed by reflexion in a plane mirror, 7. Images of a point in rippled water, 36. “Local colour,” brilliancy of: dependent on illumination, 68, 76, 78, 97; On proportion of suspended particles, 68, 83, 102; on reflective power of bottom, 70, note, 102 ; on angle of vision, 72, 75, note, 81; in reflexions of dark objects, 78, 79, note, 82, 95, 104; increased by ripple, gr. Maxwell’s colour-discs, roo, note. Mediterranean, 83, 84, 96. Mirrors, tilted to represent wave surfaces, 26. Mixture of colours, 100. Painting of reflexions in rippled water, 51. Particles, suspended, 67, 68, 83, 97: Pigments, mixture of, 100. Purple caused by mingling of tones in rippled water, 82, 99. Purple colour of shadows on snow, 108; on water, 107, IIOo. Purple colour of deep water, 96. Purple patches due to seaweed, 98. Rain falling on still water, 50. Rainbow, reflexion of, 21. Reflective power of water, 64, note, Reflexion, law of, 5. Reflexion, irregular, 9, 107. Reflexion, total internal, 61, note. ‘* Reflexion,” the observer’s view of the image, ro. Reflexions, perspective of, 18. Reflexions, elongated, 34 ef seg. ; perspective of ditto, 56; ditto inclined, 43; distorted, 55. Refraction, 61, 81. 9 Rings,” 52. Ripple interrupting the image, 31, 95. Ripple elongating the image, 34, 44, 50. Ripple reflecting light from different parts of sky, 89, 98, 99, 106. Ripple showing local colour, 91 él Seq. Rood, Prof. Ogden, tor, 108, note. Ruskin, quoted, 17, 21, 48, 59, 80. Sand, wet, reflexions in, 73, 106, 107. Sandy bottom, 70, note, 98, 103. Sea-water, colour of: Aitken on, $3; Davy on, 88; Threlfall on, S4. Seaweed, 85; purple patches caused by, 98, rio. Shade and shadow, 109. Shadows on water, 77, 81, 104, 107, I10; on snow, 107. Sky, extent of, reflected in rippled water, 47, 89, 98, 106. “Streaks,” vertical, 36 ez seg., 104;
