CHAP. V.
1. 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. Beſides there are Moderns, who with a ſlight Variation adopt the Opinion of Plato, and as he would have Colour to be nothing but a Kind of Flame conſiſting of Minute Corpuſcles as it were Darted by the Object againſt the Eye, to whoſe Pores their Littleneſs and Figure made them congruous, ſo theſe would have Colour to be an Internal Light of the more Lucid parts of the Object, Darkned and conſequently Alter'd by the Various Mixtures of the leſs Luminous
parts. There are alſo others, who in imitation of ſome of the Ancient Atomiſts, make Colour not to be Lucid ſteam, but yet a Corporeal Effluvium iſſuing out of the Colour'd Body, but the Knowingſt of theſe have of late Reform'd their Hypotheſis, by acknowledging and adding that ſome External Light is neceſſary to Excite, and as they ſpeak, Sollicit theſe Corpuſcles of Colour as they call them, and Bring them to the Eye. Another and more principal Opinion of the Modern Philoſophers, to which this laſt nam'd may by a Favourable explication be reconcil'd, is that which derives Colours from the Mixture of Light and Darkneſs, or rather Light and Shadows. And as for the Chymiſts 'tis known, that the generality of them aſcribes the Origine of Colours to the Sulphureous Principle in Bodies, though I find, as I elſewhere largely ſhew, that ſome of the Chiefeſt of them derive Colours rather from Salt than Sulphur, and others, from the third Hypoſtatical Principle, Mercury. And as for the Carteſians I need not tell you, that they, ſuppoſing the Senſation of Light to bee produc'd by the Impulſe made upon the Organs of Sight, by certain extremely Minute and Solid Globules, to which the Pores of the Air and other Diaphanous
bodies are pervious, endeavour to derive the Varieties of Colours from the Various Proportion of the Direct Progreſs or Motion of theſe Globules to their Circumvolution or Motion about their own Centre, by which Varying Proportion they are by this Hypotheſis ſuppos'd qualify'd to ſtrike the Optick Nerve after ſeveral Diſtinct manners, ſo to produce the perception of Differing Colours.
2. Beſides theſe ſix principal Hypotheſes, Pyrophilus, there may be ſome others, which though Leſs known, may perhaps as well as theſc deſerve to be taken into conſideration by you; but that I ſhould copiouſly debate any of them at preſent, I preſume you will not expect, if you conſider the Scope of theſe Papers, and the Brevity I have deſign'd in them, and therefore I ſhall at this time only take notice to you in the general of two or three things that do more peculiarly concern the Treatiſe you have now in your hands.
3. And firſt, though the Embracers of the Several Hypotheſes I have been naming to you, by undertaking each Sect of them to explicate Colours indefinitely, by the particular Hypotheſes they maintain, ſeem to hold it forth as the only Needful Theory about that Subject, yet for my part I doubt
whether any one of all theſe Hypotheſes have a right to be admitted Excluſively to all others, for I think it Probable, that Whiteneſs and Blackneſs may be explicated by Reflection alone without Refraction, as you'l find endeavour'd in the Diſcourſe you'l meet with e're long Of the Origine of Whiteneſs and Blackneſs, and on the other ſide, ſince I have not found that by any Mixture of White and True Black, (for there is a Blewiſh Black which many miſtake for a Genuine) there can be a Blew, a Yellow, or a Red, to name no other Colours, produced, and ſince we do find that theſe Colours may be produc'd in the Glaſs-priſm and other Tranſparent bodies, by the help of Refractions, it ſeems that Refraction is to be taken in into the Explication of ſome Colours, to whoſe Generation they ſeem to concurr, either by making a further or other Commixture of Shades with the Refracted Light, or by ſome other way not now to be diſcours'd. And as it ſeems not improbable, that in caſe the Pores of the Air, and other Diaphanous bodies be every where almoſt fill'd with ſuch Globuli as the Carteſians ſuppoſe, the Various kind of Motion of theſe Globuli, may in many caſes have no ſmall ſtroak in Varying our Perception of Colour, ſo
without the Suppoſition of theſe Globuli, which 'tis not ſo eaſie to evince, I think we may probably enough conceive in general, that the Eye may be Variouſly affected, not only by the Entire Beams of Light that fall upon it as they are ſuch, but by the Order, and by the Degree of Swiftneſs, and in a word by the Manner according to which the Particles that compoſe each Particular Beam arrive at the Senſory, ſo that whatever be the Figure of the Little Corpuſcles, of which the Beams of Light conſiſt, not only the Celerity or Slowneſs of their Revolution or Rotation in reference to their Progreſſive Motion, but their more Abſolute Celerity, their Direct or Undulating Motion, and other Accidents, which may attend their Appulſe to the Eye, may fit them to make Differing Impreſſions on it.
4. Secondly, For theſe and the like Conſiderations, Pyrophilus, I muſt deſire that you would look upon this little Treatiſe, not as a Diſcourſe written Principally to maintain any of the fore-mention'd Theories, Excluſively to all others, or ſubſtitute a New one of my Own, but as the beginning of a Hiſtory of Colours, upon which, when you and your Ingenious friends ſhall have Enrich'd it, a Solid Theory may be
ſafely built. But yet becauſe this Hiſtory is not meant barely for a Regiſter of the things recorded in it, but for an Apparatus to a ſound and comprehenſitive Hypotheſis, I thought fit, ſo to temper the whole Diſcourſe, as to make it as conducible, as conveniently I can to that End, and therefore I have not ſcrupled to let you ſee that I was willing, as to ſave you the labour of Cultivating ſome Theories that I thought would never enable you to reach the Ends you aim at, ſo to contract your Enquiries into a Narrow compaſs, for both which purpoſes I thought it requiſite to do theſe two things, the One, to ſet down ſome Experiments which by the help of the Reflections and Inſinuations that attend them, may aſſiſt you to diſcover the Infirmneſs and Inſufficiency both of the common Peripatetick Doctrine, and of the now more applauded Theory of the Chymists about Colour, becauſe thoſe two Doctrines having Poſſeſs'd themſelves, the one of the moſt part of the Schools, and the other of the Eſteem of the Generality ef Phyſicians and other Learned Men, whoſe Profeſſions and Ways of Study do not exact that they ſhould Scrupulouſly examine the very Firſt and Simpleſt Principles of Nature, I fear'd it would be to
little purpoſe, without doing ſomething to diſcover the Inſufficiency of theſe Hypotheſes, that I ſhould, (which was the Other thing I thought requiſite for me to do) ſet down among my other Experiments thoſe in the greateſt Number, that may let you ſee, that, till I ſhall be Better Inform'd, I encline to take Colour to be a Modification of Light, and would invite you chiefly to Cultivate that Hypotheſis, and Improve it to the making out of the Generation of Particular Colours, as I have Endeavour'd to apply it to the Explication of Whiteneſs and Blackneſs.
5. Thirdly. But, Pyrophilus, though this be at preſent the Hypotheſis I preferr, yet I propoſe it but in a General Senſe, teaching only that the Beams of Light, Modify'd by the Bodies whence they are ſent (Reflected or Refracted) to the Eye, produce there that Kind of Senſation, Men commonly call Colour; But whether I think this Modification of the Light to be perform'd by Mixing it with Shades, or by Varying the Proportion of the Progreſs and Rotation of the Carteſian Globuli Cæleſtes, or by ſome other way which I am not now to mention, I pretend not here to Declare. Much leſs do I pretend to Determine, or ſcarce ſo much as to Hope to
know all that were requiſite to be Known, to give You, or even my Self, a perfect account of the Theory of Viſion and Colours, for in Order to ſuch an undertaking I would firſt Know what Light is, and if it be a Body (as a Body or the Motion of a Body it ſeems to be) what Kind of Corpuſcles for Size and Shape it conſiſts of, with what Swiftneſs they move Forwards, and Whirl about their own Centres. Then I would Know the Nature of Refraction, which I take to be one of the Abſtruſeſt things (not to explicate Plauſibly, but to explicate Satisfactorily) that I have met with in Phyſicks; I would further Know what Kind and what Degree of Commixture of Darkneſs or Shades is made by Refractions or Reflections, or both, in the Superficial particles of thoſe Bodies, that being Shin'd upon, conſtantly exhibit the one, for Inſtance, a Blew, the other a Yellow, the third a Red Colour; I would further Know why this Contemperation of Light and Shade, that is made, for Example, by the Skin of a Ripe Cherry, ſhould exhibit a Red, and not a Green, and the Leaf of the ſame Tree ſhould exhibit a Green rather than a Red; and indeed, Laſtly, why ſince the Light that is Modify'd into theſe Colours conſiſts but of Corpuſcles
moved againſt the Retina or Pith of the Optick Nerve, it ſhould there not barely give a Stroak, but produce a Colour, whereas a Needle wounding likewiſe the Eye, would not produce Colour but Pain. Theſe, and perhaps other things I ſhould think requiſite to be Known, before I ſhould judge my Self to have fully Comprehended the True and Whole Nature of Colours; and therefore, though by making the Experiments and Reflections deliver'd in this Paper, I have endeavour'd ſomewhat to Leſſen my Ignorance in this Matter, and think it far more Deſireable to diſcover a Little, than to diſcover Nothing, yet I pretend but to make it Probable by the Experiments I mention, that ſome Colours may be Plauſibly enough Explicated in the General by the Doctrine here propos'd; For whenſoever I would Deſcend to the Minute and Accurate Explication of Particulars, I find my Self very Senſible of the great Obſcurity of things, without excepting thoſe which we never ſee but when they are Enlightned, and confeſs with Scaliger[a]5], Latet natura hæc, (ſays he, Speaking of that of Colour) & ſicut aliarum rerum ſpecies in profundiſſima caligine inſcitiæ humanæ.
