Orange. Green. Violet. _B._--Double colour sensations transmitted by unequal pairs of standard glasses. Red orange, transmitted by unequal units of red and yellow, red preponderating. Yellow orange, transmitted by unequal units of red and yellow, yellow preponderating. Yellow green, transmitted by unequal units of yellow and blue, yellow preponderating. Blue green, transmitted by unequal units of yellow and blue, blue preponderating. Blue violet, transmitted by unequal units of blue and red, blue preponderating. Red violet, transmitted by unequal units of blue and red, red preponderating. _C._--Any of the above colours with the addition or subtraction of neutral tint. Neutral tint itself, is transmitted by a combination of equal units of the standard glasses, thus three units red, yellow and blue, when superposed, transmit three units neutral tint. EXAMPLES. Three units red, of standard brightness, completely describes a colour matched by a red glass of three units, and is denoted R. 3·0 Three units red saddened by one neutral tint, completely describes a colour matched by a red glass standard of four units red, combined with a blue and yellow of one unit each, and is denoted R. 3·0 + N.T. 1·0 A given red of three units, which is one unit brighter than standards, after having been saddened by one unit each of red, yellow and blue, is matched by three units of red and is correctly described by Red 3·0 + Light 1·0 Three units of violet, of standard brightness, is matched by a red and a blue glass of three units, and is correctly described by V. 3·0 Three units of orange, of standard brightness, is matched by a red and a yellow glass of three units, and is correctly described by O. 3·0 A binary red violet of standard brightness, in which red preponderates by one unit, is matched by four units red, and a blue of three units, and is correctly described by R. 1·0 + V. 3·0 A binary red orange, of standard brightness, in which orange preponderates by three units, is matched by red four and yellow three units, and is correctly described by R. 1·0 + O. 3·0 A red orange, of less than standard brightness by one unit, in which orange preponderates by three units, is matched by a red five, yellow four, blue one, and is correctly described by R. 1·9 + O. 3·0 + N.T. 1·0 A red violet, in which red preponderates by one unit, and is one unit brighter than standard, is first dulled by one unit red, yellow and blue, and then matched by four red and three blue, and is correctly described by R. 1·0 + V. 3·0 + Light 1·0