9. But the ſame Occaſion that invited me to ſay what I have mention'd concerning the Leaves of Trees, invites me alſo to give you ſome account of what happens in Changeable Taffities, where we ſee differing Colours, as it were, Emerge and Vaniſh upon the Ruffling of the ſame piece of Silk: As I have divers times with Pleaſure obſerv'd, by the help of ſuch a Microſcope, as, though it do not very much Magnifie the Object, has in recompence this great Conveniency, that you may eaſily, as faſt as you pleaſe, remove it from one part to another of a Large Object, of which the Glaſs taking a great part at once, you may thereby preſently Survey the Whole. Now by the help of ſuch a Microſcope I could eaſily (as I began to ſay) diſcern, that in a piece of Changeable Taffity, (that appear'd, for Inſtance, ſometimes Red, and ſometimes Green) the Stuff was compos'd of Red thrids and Green, paſſing under and over each other, and croſſing one another in almoſt innumerable points; and if I look'd through the Glaſs upon any conſiderable portion of the Stuff, that (for example ſake) to the
naked Eye appear'd to be Red, I could plainly ſee, that in that Poſition, the Red thrids were Conſpicuous, and reflected a vivid Light; and though I could alſo perceive, that there were Green ones, yet by reaſon of their diſadvantagious Poſition in the Phyſical Surface of the Taffity, they were in part hid by the more Protuberant Thrids of the other Colour; and for the ſame cauſe, the Reflection from as much of the Green as was diſcover'd, was comparatively but Dim and Faint. And if, on the contrary, I look'd through the Microſcope upon any part that appear'd Green, I could plainly ſee that the Red thrids were leſs fully expos'd to the Eye, and obſcur'd by the Green ones, which therefore made up the Predominant Colour. And by obſerving the Texture of the Silken Stuff, I could eaſiſy ſo expoſe the Thrids either of the one Colour or of the other to my Eye, as at pleaſure to exhibit an apparition of Red or Green, or make thoſe Colours ſucceed one another: So that, when I obſerv'd their Succeſſion by the help of the Glaſs, I could mark how the Predominant Colour did as it were ſtart out, when the Thrids that exhibited it came to be advanagiouſly plac'd; And by making little Folds in the Stuff after a certain manner,
the Sides that met and terminated in thoſe Folds, would appear to the naked Eye, one of them Red, and the other Green. When Thrids of more than two differing Colours chance to be Interwoven, the reſulting changeableneſs of the Taffity may be alſo ſomewhat different. But I chooſe to give an Inſtance in the Stuff I have been ſpeaking off, becauſe the mixture being more Simple, the way whereby the Changeableneſs is produc'd, may be the more eaſily apprehended: and though Reaſon alone might readily enough lead a conſidering Man to gueſs at the Explication, in caſe he knew how Changeable Taffities are made: yet I thought it not impertinent to mention it, becauſe both Scholars and Gentlemen are wont to look upon the Inquiry into Manufactures, as a Mechanick imployment, and conſequently below Them; and becauſe alſo with ſuch a Microſcope as I have been mentioning, the diſcovery is as well Pleaſant as Satisfactory, and may afford Hints of the Solution of other Phænomena of Colours. And it were not amiſs, that ſome diligent Inquiry were made, whether the Microſcope would give us an account of the Variableneſs of Colour, that is ſo Conſpicuous and ſo Delightfull in Mother of Pearl, in Opalls, and ſome
other reſembling Bodies: For though I remember I did formerly attempt ſomething of that Kind (fruitleſly enough) upon Mother of Pearl, yet not having then the advantage of my beſt Microſcope, nor ſome Conveniences that might have been wiſh'd, I leave it to you, who have better Eyes, to try what you can do further; ſince 'twill be Some diſcovery to find, that, in this caſe, the beſt Eyes and Microſcopes themſelves can make None.
10. I confeſs, Pyrophilus, that a great part of what I have deliver'd, (or propos'd rather) concerning the differing forms of Aſperity in Bodies, by which Differences the incident Light either comes to be Reflected with more or leſs of Shade, and with that Shade more or leſs Interrupted, or elſe happens to be alſo otherwiſe Modify'd or Troubl'd, is but Conjectural. But I am not ſure, that if it were not for the Dullneſs of our Senſes, either theſe or ſome other Notions of Kin to them, might be better Countenanc'd; for I am apt to ſuſpect, that if we were Sharp ſighted enough, or had ſuch perfect Microſcopes, as I fear are more to be wiſh'd than hop'd for, our promoted Senſe might diſcern in the Phyſical Surfaces of Bodies, both a great many latent Ruggidneſſes, and the particular
Sizes, Shapes, and Situations of the extremely little Bodies that cauſe them, and perhaps might perceive among other Varieties that we now can but imagine, how thoſe little Protuberances and Cavities do Interrupt and Dilate the Light, by mingling with it a multitude of little and ſingly undiſcernable Shades, though ſome of them more, and ſome of them leſs Minute, ſome leſs, and ſome more Numerous; according to the Nature and Degree of the particular Colour we attribute to the Viſible Object; as we ſee, that in the Moon we can with Excellent Teleſcopes diſcern many Hills and Vallies, and as it were Pits and other Parts, whereof ſome are more, and ſome leſs Vividly illuſtrated, and others have a fainter, others a deeper Shade, though the naked Eye can diſcern no ſuch matter in that Planet. And with an Excellent Microſcope, where the Naked Eye did ſee but a Green powder, the Aſſisted Eye as we noted above, could diſcern particular Granules, ſome of them of a Blew, and ſome of them of a Yellow colour, which Corpuſcles we had beforehand caus'd to be exquiſitly mix'd to compound the Green.
11. And, Pyrophilus, that you may not think me altogether extravagant in what I
have ſaid of the Poſſibility, (for I ſpeak of no more) of diſcerning the differing forms of Aſperity in the Surfaces of Bodies of ſeveral Colours, I'l here ſet down a Memorable particular that chanc'd to come to my Knowledge, ſince I writ a good part of this Eſſay; and it is this. Meeting caſually the other Day with the deſervedly Famous[a]4] Dr. J. Finch, Extraordinary Anatomiſt to that Great Patron of the Virtuoſi, the now Great Duke of Toſcany, and enquiring of this Ingenious Perſon, what might be the chief Rarity he had ſeen in his late return out of Italy into England, he told me, it was a Man at Maeſtricht in the Low-Countrys, who at certain times can diſcern and diſtinguiſh Colours by the Touch with his Fingers. You'l eaſily Conclude, that this is farr more ſtrange, than what I propos'd but as not Impoſſible; ſince the Senſe of the Retina ſeeming to be much more Tender and quick than that of thoſe Groſſer Filaments, Nerves or Membranes of our Fingers, wherewith we uſe to handle Groſs and Hard Bodies, it ſeems ſcarce credible, that any Accuſtomance, or Diet, or peculiarity of Conſtitution, ſhould enable a Man to diſtinguiſh
with ſuch Groſs and Unſuitable Organs, ſuch Nice and Subtile Differences as thoſe of the forms of Aſperity, that belong to differing Colours, to receive whoſe Languid and Delicate Impreſſions by the Intervention of Light, Nature ſeems to have appointed and contexed into the Retina the tender and delicate Pith of the Optick Nerve. Wherefore I confeſs, I propos'd divers Scruples, and particularly whether the Doctor had taken care to bind a Napkin or Hankerchief over his Eyes ſo carefully, as to be ſure he could make no uſe of his Sight, though he had but Counterfeited the want of it, to which I added divers other Queſtions, to ſatisfie my Self, whether there were any Likelihood of Colluſion or other Tricks. But I found that the Judicious Doctor having gone farr out of his way, purpoſely to ſatisfie Himſelf and his Learned Prince about this Wonder, had been very Watchfull and Circumſpect to keep Himſelf from being Impos'd upon. And that he might not through any miſtake in point of Memory mis-inform Me, he did me the Favour at my Requeſt, to look out the Notes he had Written for his Own and his Princes Information, the ſumm of which Memorials, as far as we ſhall mention them here, was this, That the Doctor
having been inform'd at Utrecht, that there Lived one at ſome Miles diſtance from Maestricht, who could diſtinguiſh Colours by the Touch, when he came to the laſt nam'd Town, he ſent a Meſſenger for him, and having Examin'd him, was told upon Enquiry theſe Particulars: