CORRESPONDENCE Oi' RAY. 71 



white paper with the juice. Those trials he made by the 

 infusion of the flowers themselves, sometimes succeeded, 

 and sometimes not ; but I do not value any exception 

 made against the rule, if it be grounded upon either of 

 these two latter ways of examination ; for if in a great 

 glass full of juice of betony you can perceive but a very 

 Hglit vestigium of redness, although you hold it so that 

 the rays of light are refracted through the whole mass, 

 what can we then expect to see in a paper slightly 

 moistened with that juice, or a thin leaf of a flower? 

 You may satisfy yourself that spirit of salt hath turned 

 blue juices red, if you please to consult Mr. Boyl's Book 

 of Colours, Part 3, Experiments 20 and 21 . There you 

 will see it hath changed syrup of violets and juice of 

 blue-bottles, and I doubt not but it will change also 

 chicory flowers, though perhaps with some variety, if the 

 trial be made as it was there. 



The only general exception that Mr. Fisher knows of 

 is, that acid spirits do not work upon juices of plants or 

 fruits that are very acid. Juice of lemons, they say, will 

 not change by the infusion of any acid spirit they know 

 of, — no, not by standing long, and corruption, which 

 will change the juices of many other fruits or plants, 

 although they be acid. They have also made trial of 

 white currants, but cannot perceive that acid spirits alter 

 them. The reason, I suppose, why juices turn red by 

 standing is, that in time, by a long fermentation, the 

 acid spirit loosens itself from the other parts, and then 

 works the same effect upon them which an infused spirit 

 doth at first. I infused wallflowers in spirit of salt, as 

 Mr. Boyl somewhere saith he did leaves of yellow roses, 

 but could observe no change \ and yet I am not satisfied 

 fully, until I make trial of a considerable quantity of the 

 juice. I told you that alkalies restored juices to their 

 natural colours again, but I must recant ; for although it 

 happened to fall out so in some trials I saw made, yet 

 they say generally they turn them into green, or at least 

 some colour that hath some tincture of green ; but yet 



