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I know not, Pyrophilus, whether it be worth while to acquaint you with the ways that came into my Thoughts, whereby in some measure to explicate the first of the mention'd ways of making a Green; for I have sometimes Conjectur'd, that the mixture of the Bise and the Orpiment produc'd a Green by so altering the Superficial Asperity, which each of those Ingredients had apart, that the Light Incident on the mixture was Reflected with differing Shades, as to Quantity, or Order, or both, from those of either of the Ingredients, and such as the Light is wont to be Modify'd with, when it Reflects from Grass, or Leaves, or some of those other Bodies that we are wont to call Green.
And multitudes of Bodies there are, whose Fragments seem Opacous to the naked Eye, which yet, when I have included them in good Microscopes, appear'd Transparent; but, Pyrophilus, on the other side I am not yet sure that there are no Bodies, whose Minute Particles even in such a Microscope as that of mine, which I was lately mentioning, will not appear Diaphanous.
Meeting the other day, Pyrophilus, in an Italian book, that treats of other matters, with a way of preparing what the Author calls a Lacca of Vegetables, by which the Italians mean a kind of Extract fit for Painting, like that rich Lacca in English commonly call'd Lake, which is imploy'd by Painters as a glorious Red.
And other Examples might be added of this way of producing Whiteness in Bodyes by Præcipitating them out of the Liquors wherein they have been Dissolv'd; but I think it may be more usefull to admonish you, Pyrophilus, that this observation admits of Restrictions, and is not so Universal, as by this time perhaps you have begun to think it; For though most Præcipitated Bodyes are White, yet I know some that are not; For Gold Dissolv'd in Aqua Regis, whether you Præcipitate it with Oyl of Tartar, or with Spirit of Sal Armoniack, will not afford a White but a Yellow Calx.
And I know not, Pyrophilus, whether I might not add, that even the Motion of the Small Parts of a Visible Object may in some cases contribute, though it be not so easie to say how, to the Producing or the Varying of a Colour; for I have several times made a Liquor, which when it has well settled in a close Vial, is Transparent and Colourless, but as soon as the Glass is unstopp'd, begins to fly away very plentifully in a White and Opacous fume; and there are other Bodies, whose Fumes, when they fill a Receiver, would make one suspect it contains Milk, and yet when these Fumes settle into a Liquor, that Liquor is not White, but Transparent; And such White Fumes I have seen afforded by unstopping a Liquor I know, which yet is it self Diaphanous and Red; Nor are these the only Instances of this Kind, that our Tryals can supply us with.
By what has been hitherto discours'd, Pyrophilus, we may be assisted to judge of that famous Controversie which was of Old disputed betwixt the Epicureans and other Atomists on the one side, and most other Philosophers on the other side.
There are you know, Pyrophilus, besides those Obsolete Opinions about Colours which have been long since Rejected, very Various Theories that have each of them, even at this day, Eminent Men for its Abetters; for the Peripatetick Schools, though they dispute amongst themselves divers particulars concerning Colours, yet in this they seem Unanimously enough to Agree, that Colours are Inherent and Real Qualities, which the Light doth but Disclose, and not concurr to Produce.
But those hinted, Pyrophilus, I must now leave such as You to prosecute, having already spent farr more time than I intended to allow my self in acquainting You with particular Experiments and Observations concerning the changes of Colour, to which I might have added many more, but that I hope I may have presented You with a competent number to make out in some measure what I have at the beginning of this Essay either propos'd as my Design in this Tract, or deliver'd as my Conjectures concerning these matters.
But, Pyrophilus, both the Nature of the Colours, and the Degree of Transparency, or of Darkness in the Pigment, besides divers other Circumstances, did so vary the Phænomena of these Tryals, that till I can procure small Colour'd Prisms, or Hollow ones that may be filled with Tincted Liquor, or obtain Some better Pigments than those I was reduc'd to imploy, I shall forbear to Build any thing upon what has been delivered, and shall make no other use of it, than to invite you to prosecute the Inquiry further.
By all this You may see, Pyrophilus, the reasonableness of what we elsewhere had occasion to mention, when we have divers times told you, that it is usefull to have New Experiments try'd over again, though they were, at first, made by Knowing and Candid Men, such Reiterations of Experiments commonly exhibiting some New Phænomena, detecting some Mistake or hinting some Truth, in reference to them, that was not formerly taken notice of.
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