70 COERESPONDENCE OF RAY. 



He desires that it may be tried, to see whether it will do 

 the like with others. It worked not until the second 

 day. 



Mr. Fisher thinks that the small quantity of spirit of 

 sulphrn-, added for the keeping of the juices, may contri- 

 bute to the increase of their redness, but not altogether 

 cause it ; for he observes, that the same juices, unmixed, 

 will grow red with standing. 

 October 24, 1670. 



Mr. Jessop's Letter to Mr. Eay (without date). 



Sir, — In answer to yoiu* last, I say, that although it 

 pass for a general rule, that acid spnits change the juices 

 of herbs, flowers, and berries into red, or a colour some- 

 thing inclining to red (for you will find a variety almost 

 in every experiment you shall make), yet I intend not 

 thereby that the rule should be so general as to admit of 

 no exceptions ; and yet I believe that, if the experiment 

 be made with care, there will be found fewer exceptions 

 than you will be apt at fii-st to imagine. I believe Dr. 

 Hulse's experiment upon chicory flowers might have the 

 success you relate ; for the juices of all flowers are in- 

 cluded in a membrane, which some spirits, although they 

 seem very acid, yet may not pierce, and so not work the 

 effect upon the included juice. To confirm this, I re- 

 member that once we put either borage or chicory 

 flowers, I cannot well tell which, into cold vinegar, and 

 we could not perceive the colour to alter, although we 

 let it stand for a considerable time ; but, heating the 

 same vinegar, and putting other flowers in, they imme- 

 diately changed, the heat, as I suppose, softening the 

 membrane, and so opening a passage for the vinegar into 

 the juice. Mr. Boyl's experiments were made upon ex- 

 pressed juices, either in glass phials, which questionless is 

 the best way, or by bruising the flower, and staining a 



