24 



fal yellow. Violets, roses, carnations, and most flowers 

 lose their colour, by being long in the open air. And by 

 the same means blue essential oil of chamomile-flower* 

 changes to a dirty green. 



Many colours may be produced, destroyed, and re- 

 generated, upon simple mixture. Let dried rose-leaves 

 stay awhile in spirits of wine, and they lose their colour 

 without tinging the liquor. But add a little oil of vitriol, 

 and it turns red : put in a little urinous spirit, and the 

 red changes to green, which by adding a little more oil 

 of vitriol, turns to a red again. 



Make a slight infusion of bruised galls in water, so as 

 not to discolour it. Make also a weak infusion of green 

 vitriol in water, which will be still transparent. Yet mix 

 them together, and an inky blackness will immediately 

 arose. But add a little oil of vitriol, the blackness will 

 vanish, and the liquor be transparent again. Yet the 

 blackness may be recalled by adding a little salt of 

 tartar. 



If a little bruised camphire which is very white, be 

 put into transparent oil of vitriol, the camphire will dis- 

 solve, and tinge the liquor first brown, and at length a 

 fine black. But upon the addition of fair water, t)ie 

 blackness entirely vanishes, and the camphire regains its 

 native whiteness. 



A transparent infusion of sugar of lead in water being 

 wrote with, when dried becomes invisible. But the bare 

 fumes of another transparent liquor, namely, infusion of 

 quick lime and orpiment in water, will quickly make the 

 invisible writing black and visible. 



And not only secondary, but primary colours are pro- 

 ducible by simple mixture. If the sun's rays pass 

 through two pieces of differently coloured glass, sup- 

 pose a blue and a yellow piece laid on each other, and 

 these rays are received upon white paper, they produce a 

 beautiful green. A mixture of seven, or even five, ori- 

 ginal colours, will make a pure white. If different co- 

 loured flames be brought to mix, the experiment is 

 made to perfection. 



flames from different bodies are of different colours. 



