§55 XXI. COLOURED PAPERS. 163 



hue of No. 6 would be better than No. 12. The most 

 fatiguing is a red ground, as Nos. 15 and 17; and red, which 

 tries the eye in the day, is far more exhausting by candle- 

 light. A glazed paper should also be avoided. 



It is found that (the letters being in black ink) ochrous 

 yellow paper is the best for the eyes by candlelight ; though 

 not so perhaps in full daylight. When too yellow it is trying 

 to the eye. Fawn-colour is good in a strong light, but not 

 bright enough in a dull light. Orange-yellow is very dis- 

 tinct, but too bright for the eye. Lemon-colour is also dis- 

 tinct from contrast, but fatiguing to the sight. Stone-colour, 

 of a yellowish tinge, is clear and comfortable to the eye. 

 Light green stone-colour is the most agreeable of the green 

 tints. Light grass and pea-green are distinct : other greens 

 not so distinct. Light lilac and lavender are also comfortable 

 to the eye, provided they have not too much blue. Light 

 pink is distinct, but not comfortable to the eye, and better for 

 a dull than a bright light. Ked-orange is a contrast which 

 makes the black distinct, but is not comfortable to the eye. 

 Salmon-colour is distinct, but trying to the eye. Light ochrous- 

 colour is better for the eye (as No. 4 of last page). The black 

 of the ink even changes its appearance on certain coloured 

 papers ; as on a red and a green ground ; and on a yellow- 

 green (or on a pistachio-coloured) paper it has a reddish- 

 brown tinge ; so too a red ink on green paper looks russet. 



In all cases where the eye is weak, or when it is much 

 employed by night, the light of lamps or candles should be 

 tempered by covering them with a blue glass shade, in order 

 to obviate the red and yellow rays, and to bring the light as 

 near as possible to that of day; there should also be a 

 sufficient quantity of light to see distinctly, and nothing is 

 more trying to the eye than reading by a dull or iD sufficient 

 light. But as, in order to overcome the red or yellow rays of 

 a lamp, the blue glass must necessarily have a considerable 



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