Now whether the Air perform these things by the means of a Subtile Salt, which we elsewhere show it not to be destitute of, or by a peircing Moisture, that is apt easily to insinuate it self into the Pores of some Bodies, and thereby change their Texture, and so their Colour; Or by solliciting the Avolation of certain parts of the Bodies, to which 'tis Contiguous; or by some other way, (which possibly I may elsewhere propose and consider) I have not now the leisure to discourse. And for the same reason, though I could add many other Instances, of what I formerly noted touching the emergency of Redness upon the Digestion of many Bodies, insomuch that I have often seen upon the Borders of _France_ (and probably we may have the like in _England_) a sort of Pears, which digested for some time with a little Wine, in a Vessel exactly clos'd, will in not many hours appear throughout of a deep Red Colour, (as also that of the Juice, wherein they are Stew'd, becomes) but ev'n on pure and white Salt of Tartar, pure Spirit of Wine, as clear as Rock-water, will (as we elsewhere declare) by long Digestion acquire a Redness; Though I say such Instances might be Multiply'd, and though there be some other Obvious changes of Colours, which happen so frequently, that they cannot but be as well Considerable as Notorious; such as is the Blackness of almost all Bodies burn'd in the open Air: yet our haste invites us to resign you the Exercise of enquiring into the Causes of these Changes. And certainly, the reason both _why_ the Soots of such differing Bodies are almost all of them all Black, _why_ so much the greater part of Vegetables should be rather Green than of any other Colour, and particularly (which more directly concerns this place) _why_ gentle Heats do so frequently in Chymical Operations produce rather a Redness than another Colour in digested _Menstruums_, not only Sulphureous, as Spirit of Wine, but Saline, as Spirit of Vinegar, may be very well worth a serious Inquiry; which I shall therefore recommend to _Pyrophilus_ and his Ingenious Friends. [21] _Parkinson_, Thea. Bot. Trib. 4 cap. 12. _EXPERIMENT XXXVII._