Physiologia Epicuro-Gassendo-Charltoniana, or, A fabrick of science natural, upon the hypothesis of atoms founded by Epicurus repaired [by] Petrus Gassendus ; augmented [by] Walter Charleton ...

SECT. III.

TO descend to Particulars. It being more than probable,* 1.1 that the various species of Colours have their Origine from only the various Manners, in which the incident particles of Light, reflected from the exteriours of Objects, strike and affect the principal sensory; it cannot be improbable, that the sense of a White Colour is caused in the Optick Nerve, when such Atoms of light, or rayes consist∣ing of them, strike upon the Retina Tunica, as come Directly from the Lucid Fountain, the Sun, or pure Flame; or Reflexedly from a body, whose superficial particles are Polite and Sphaerical, such as we have former∣ly conjectured in the smallest and hardly distinguishable Bubbles of Froth, and the minute particles of Snow.

And, as for the perception of its Contrary, Black, generally,* 1.2 though scarce warrantably reputed a Colour; we have very ground for our conjecture, that it ariseth rather from a meer Privation of Light, than any Material Impression on the sensory. For, Blackness seems identical, or coessential with Shadow: and all of it that is positively per∣ceptible, consisteth in its participation of Light, which alone cau∣seth it not to be absolutely Invisible. And hence is it, that we have se∣veral Degrees, or gradual Differences of Black, comparative to the se∣veral degrees of shadow, progressing till we arrive at perfect Darkness: and that we can behold nothing so black, which may not admit of dee∣per and deeper blackness, according to its greater and greater recess from light, and nearer and nearer access to absolute Opacity. To reason, therefore, is it consonant that all Bodies, whose natural Hew is Black, are composed of such insensible particles, whose surfaces are scabrous, rough, or craggy, and their Contexture so Rare, or loose, as that they rather imbibe, or swallow up the incident rayes of light, than reflect them outwardly to∣ward the eye of the Spectator. Of this sort, the most memorable, yet discovered, is the Obsidian stone, so much admired and celebrated among the Romans; whose substance being conflated of scabrous and loosely contexed Atoms, causeth it to appear a perfect Negro, though held in the Meridian Sun-shine: because the rayes invading it are for the most part, as it were absorpt and stifled in the small and numerous Ca∣verns and Meanders variously interspersed among its component particles. Which common and illiterate eyes beholding, delude their curiosity with this refuge; that it hath an Antipathy to Light, and doth therefore reflect it converted into shadows.

The Generation of the Two Extreme and Ground Colours,* 1.3 White and Black, being attained by this kind of inquest into the Rolls of reason; the Former deriving it self from Light; either immediately and in direct lines profluent from its fountain; or by reflection from bodies, whose superficial particles are sphaerical and polite; the Later from the Negation of Light: there can be no great difficulty remaining concerning the Ge∣nealogy of all other INTERMEDIATE ones, since they are but

the off-spring of the Extreme, arising from the intermission of Light and shadow, in various proportions; or, more plainly, that the sense of them is caused in the Retina Tunica, according to the variety of Reflections and Refractions, that the incident Light suffers from the superficial parti∣cles of objects, in manner exactly analogous to that of the Evanid Colours, observed in sphaerical Glasses, replete with Water, in Prismes interposed betwixt the object and eye, in angular Diamonds, Opalls, &c. For, even our sense demonstrates, that they are nothing, but certain Perturbations, or Modifications of Light, interspersed with Umbrellaes, or small sha∣dows.

* 1.4The Verisimility of this may be evinced from the Sympathy and Anti∣pathy of these intermediate Colours, among themselves. For, the Reason, why Yellow holds a sympathy, or symbolical relation with Vermillion and Green, and Green with Sky-colour and Yellow, (as the experience of Pain∣ters testifieth, who educe a yellow Pigment out of Vermillion and Green, in due proportions commixt, upon their Palatts: and reciprocally, Green out of Yellow and Sky-colour, in unaequal but determinate quantities contempered) is no other but the Affinity of their respective Causes, or only gradually different manners of Light reflected and refracted, and in∣termixt with minute and singly imperceptible shadows. And, on the con∣trary, the Reason of the Antipathy, or Asymbolical relation betwixt a saf∣fron Yellow and a Caerule, betwixt a Green and a Rose colour, into which a saffron yellow degenerates, and betwixt a Yellow and Purple, into which a Caerule degenerates: can be nothing else, but the Dissimilitude or Remote∣ness of their respective Causes; since things so remotely Discrepant, are incapable of Conciliation into a Third, or Neutral, or (rather) Amphidecti∣cal Nature, but by the mediation of something, that is participant of both. This the Philosopher glanced at in his; Colores misceri videntur, quemadm••∣dum soni; ita enim qui eximium quoddam proportionis genus servant, hi Consonantiarum more, omnium suavissimi sunt, ceu purp••reus & puniceus, &c. (de sens. & sensil. cap. 3.)

* 1.5We say, that all these Intermediate Colours emerge from the various in∣termistion of Light, and small shadows; because, to the production of each of them from reflected, or refracted Light, or both, the interpositi∣on of minute, and separately invisible shadows, is indispensably Necessary. Which may be evidenced even from hence, that Colors are not by Prismes appinged on bodies, but in their Margines or Extremes, there where is not only the general Commissure of Light and Shadows; but also an Inaequa∣lity of superfice: which, by how much the more scabrous or rough, by so much the more are the Colours apparent thereon, ampliated in Latitude. For, since there is no superfice, however smooth and equal to the sense, devoid of many Extancies and Cavities; as we have more then once pro∣festly declared: it is of necessity, that betwixt the confronting sides of the Extancies, reflecting the rays of light hither and thither, there should be in∣tercedent small shadows, in the interjacent Cavities, from which no light is reflected. And hence is it, that in an object speculated through a Prism, the Caerule colour appears so much the more Dense and lively, by how much the nearer to the limbus, or Extreme of the Object it is appinged; be∣cause, in that place, is the greater proportion of small shadows: and è contra, so much more Dilute and Pale▪ by how much farther it recedeth from the

Margin, insomuch that it degenerates, or dwindles at last into weak Sea-Green, or Willow, in its inmost part; because, in that place is the greater proportion of Light. Conformable to that rule of Athanas. Kircher. (Art. Magn. Lucis & Umbrae. lib. 1. part. 2. cap. 1.) Differunt autem & Umbra & Fulgores, majore & minore vel candore, & nigrore, prout vel Fonti lucis, aut tenebrarum propriores fuerint, vel à fonte longius recesserint, in quo luce & obscuritate summa sunt utraque. Unde patet, quantò Fulgores a luce magis recesserint, tanto plus Nigredinis; & quantò a tenebris magis recesserint Umbrae, diminuto nigrore, tanto plus albedinis acqui∣rere: quae omnia Visus judicare potest. The same, proportionately, we con∣ceive to hold good also in all Bodies, whose Colours are Genuine, or ap∣parent to the naked Eye: chiefly because we may lawfully conceive, that every particle of every hair in a Scarlet, or Violet coloured Cloth, is consimilar in disposition to the particles in the extremes of an Object speculated through a Prism: and hold it purely Consequential thereupon, that light may arrive at the Eye from them, with the like Reflections and Intermistion with shadows, as from the extremes of the Reflectent Body, through the Glass, which advanceth its commixture with small shadows. And what we affirm of Scarlet and Violet, may also, with no less Congruity, be accommodated to Yellow and Sea-Green; allowing the same proportion and modification of Light and Sha∣dows in them as in that part of the superfice of any other body, on which the Prism doth appinge them: and in like manner to all other Colorate objects, whose Tinctures bear any Affinity to either of these four specified, or arise from the Complexion of any two or more of them.

But here we are arrested by Two notable,* 1.6 and to our praecedent theory seemingly inconsistent PROBLEMS: which though of Diffi∣culty enough to deserve the wealthy speculations of Archimedes, do yet require from us at least a plausible Solution, on the paenalty of no less than the loss of reputation, and the posting up a Writ of Bankrupt against our reason, by that austere Creditor, Curiosity.

(1) How comes it, that those two so discrepant and assymbolical Co∣lours, created by a Prism, Vermillion and Caerule, arise from Causes so Cog∣nate; the former only from the Commistion of a greater proportion of Light with a less of Shadows; the Later from a less proportion of Light with a greater of Shadows?

(2) Why, when those two Colours Emphatical, Vermillion and Carule are by a Prism intermediate, projected on a Wall or sheet of white paper beyond it, from the light of a Candle; if you put your eye in that place, ••n which either of the two Colours is appinged, so that another person, con∣veniently posited in the same room, may behold the same distinctly shining on the pupil of your eye; yet shall you plainly and distinctly perceive the other Colour in the Glass? For Example; if the Vermillion appear on your eye, you shall nevertheless clearly see a Caerule in the Glass: and transpositively, though your eye be manifestly and totally tincted with a Carule, yet shall you see a Vermillion.

* 1.7Touching the Former, we shall adventure to desume the Solution thereof meerly from the Figure of the Prisme, and determine the Reason on this only; that the Rayes of Light arriving at the Base of the Triangle, are trajected through it by a longer tract or way, than those arriving at or nearer to the Top thereof: and therefore, the Glass being in that part most crass, there must be more impervious particles obsistent to the Rayes of Light; each one whereof reper∣cussing its raye back again into the medium from the Glass, causeth that the number of shadowes is multiplyed in that part of the ob∣ject, which the Base of the Triangle directly respecteth; and con∣sequently produceth a Caerule Tincture thereon. Such as that, not only by vulgar, but many transcendently learned Heads adscribed to the Firmament▪ which yet belongs rather to that vast (many have said infinite) Space betwixt it and our Terrestrial Globe, being caused by the rayes of the Coelestial Lamps, from swarms of minute bodies interposed, thinly reflected toward our eyes: For, each of those im∣pervious particles swarming in that immense space, must repercuse a ray of Light deradiated from above, and so by multiplying the number of shadows, make the Firmament (which otherwise, according to probabi∣lity, would wear the mourning livery of Midnight) appear totally in∣vested in an Azure mantle.

This, though meer Conjecture (and, indeed, the subject is too sub∣lime to admit of other than conjecture, since St. Paul hath left us no observation concerning it, in his rapture up into the third Heaven, and the design of the Ganzaes is desperate) hath in it somewhat more of reason, then that confident conceipt of Athanas. Kircherus (Art. Magn. lucis & umbrae, lib. 1. part. 3. cap. 3. de Chromatismis rerum naturali∣um.) Medium inter utrumque Caeruleum, proximum, viz. à nigro, seu tenebroso, colorem ad jucundissima illa Caelorum spatia, inoffenso visu con∣templanda, Natura providentissima mundo contulit, &c.

that the Providence of the Creator chose this Azure Tincture to invest the Firmament withal, as the middle colour between the two Extreams, White and Black, that so our sight might not, when we speculate that universal Canopy, be either perstringed with the excessive lustre of the one, nor terminated by the absolute opacity of the other.

Be∣cause, if the natural Colour of the Firmament were Azure, as He prae∣sumes; then would it, by reason of the vast Space betwixt it and our sight, and the repercussion of the greatest part of the rayes of Light, from our eye, by those Myriads of Myriads of Myriads of small bodies replenishing that intermediate Space, necessarily appear of some o∣ther colour: the experience of Sea-men assuring, that all Colours, (White and that of pure Flame, retaining to Whiteness, only excep∣ted) lose themselves in long trajection through the medium, and that even Land, which is but few degrees removed from Opacity, appears to the first discovery like a blewish Cloud lying level to the Horizon. It being certain, therefore, that by how much the farther any Colour recedeth from Whiteness, by so much the less way it is visible (which the Graecian intimates in the word, 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉, Albus, 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉, quod procul videatur.) and that even the Earth, an Opace body, to Sea-men first Kenning it, at large distance, ap∣pears clad in a kind of obscure blewish Mantle: it cannot bee

dissonant to reason to conceive, that the natural Colour of the Firma∣ment cannot be Azure, since it so appears to us; and that it is rather Opace, because it appears Azure, when illustrate by the reflected Light of the Coelestial Luminaries.

Again, because the rayes of Light, incident on the Top of the Prism, are trajected through it by a shorter cut, or passage, than those incident on the Base; and so meet with fewer impervious and retundent particles, the Glass being in that part thinnest: therefore is the number of shadows much less in that part of the object, which respecteth the Cone or Top of the Triangle, than in that, which confronts the Base; and those few sha∣dows which remain undiminisht, being commixt with a greater number of lines of light, are transformed into the species of a Vermillion Red. Such as that daily observed in the impure Flame of our Culinary Fires; which having many particles of Fuligenous Exhalations commixt with its pure luminous particles, that continuedly ascending, avert as many rayes of light from the eye of the Spectator, and so in some degree obnubulate it through∣out: doth therefore put on the semblance of Redness. Or such as the Sun and Moon, commonly wear at their rising; when the minor part, though many of their rayes are re••used, and averted from our sight, by the particles of dense vapours diffused through the spatious Medium.

However this may be disputed, yet is it warrantable to conceive, that the superficial Particles of all Bodies, clad in either of these Liveries, Ver∣million and Caerule, may have in their Contexture obtained such a Disposi∣tion, as to reflect Light permixt with small shadows, in that definite Tem∣peration, or Modification, in which it usually arrives at the eye, after its Trajection through a Prism; when it thereupon impresseth the sense of a Vermillion, or Caerule.

As for the Enodation of the Later Difficulty,* 1.8 it is comprehended in the Reasons of the Former. For, it being certain, that the Vermillion projected by a Prisme, doth consist of a greater proportion of Light min∣gled with a less of Shadows, and the Caerule, on the contrary, of a grea∣ter proportion of shadows interspersed among the lines of a less Light; and as certain, that the Vermillion appeareth on that side of the Prisme, where the Light is more copious, as therein meeting with fewer retundent impervious particles, in the substance of the Glass; and the Caerule in that part, where the Light is diminished, as meeting with more impervious particles, and being by them repercussed: it must inevitably follow thereupon, that, if an opacous body be posited within the bounds of this light, so that the light may fall on each side thereof, and as it were fringe it; a symptome quite contrary to the former shall evene, i. e. the Vermillion will appear on that side of the species, which is over against the Caerule, and the Caerule will be transposed to that side of the species, which confronteth the Vermillion. This is easily Experimented with a piece of narrow black Ribbon affixt longwise to either side of the Prisme. For, in that case, the light is bipartited into two Borders, or Fringes, the opace part veyled by the Ribbon on each side environed with light, and each border of light environed with two shadows; or, more plainly, between each border of sha∣dows conterminate to each extreme of Light, trajected through the

unopacate parts of the Glass: and, therefore, in the commissure of each of the two lights with each of the conterminous shadows, there must be Ver∣million on one side, and Caerule on the other.

Now to drive this home to the head, the solution of the present Problem; the Reason why, when the light of a Candle is trajected through a Prism, on a White paper or Wall, posited at convenient distance beyond it, and there transformed into these two luminous Colours, Vermillion and Caerule, if you put your eye in that place of the Paper or Wall, whereon the Vermil∣lion shines, you shall perceive only the Caerule in the Glass, and è contra: we say, the Reason of this alteration of site in the Colours seems to be on∣ly this, that the circumstant Aer about the flame of the Candle being opa∣cous, and so serving in stead of two Blacks to environ the borders of light, causeth that side of the Candle, which is seen through the thicker part of the Glass, to appear Blew; and that which is seen through the thinner, to appear Red; according to the constant Phaenomenon in Prismes. But, if the species be beheld by Reflection from any illustrate and repercussing Bo∣dy, such as the paper, or wall, then must the series or method of the borders of light and shadow be inverted, for the reason immediately praecedent, and consequently, the situation of the Colours, emergent from their various contemperations, be also inverted.

* 1.9And thus have we, by the twilight of Rational Conjecture, given you a glimpse of the abstruse Original of the Extreme and Simple Colours; and should now continue our Attempt to the discovery of the Reasons of each of those many COMPOUND ones, wherewith both Nature and Art so delightfully imbellish most of their peices: but, since they are as Generally, as rightly praesumed to be only the multiplied removes of Light and Dark∣ness, i. e. to be educed from the various Commixtures of the Extreme, or Simple, or both; and so it cannot require but a short exercise of the Intellect to investigate the determinate proportions of any two, or more of the Simple ones, necessary to the creation of any Compound Colour assigned (especially when those excellent Rules of that Modern Apelles, Albertus Durerus, praescribed in his Art of Limning; and the common Experience of Painters, in the Confection of their several Pigments, afford so clear a light toward the remove of their remaining obscurity, and the singling out their particular Natures): we cannot but suppose, that any greater super∣structure on this Foundation, would be lookt upon rather as Ornamental and Superfluous, than Necessary to the entertainment of moderate Curiosi∣ty. Especially when we design it only as a decent Refuge, for the shelter of ingenious Heads from the Whirlwind of Admiration: and not as a constant Mansion for Belief.* 1.10

For, as we cautiously praemonished, in the First Article, the Foundation of it is not layed in the rock of absolute Demonstration, or de••umed a Prio∣ri; but in the softer mould of meer Conje••ture, and that no deeper than a Posteriori. And this we judge expedient to profess, because we would not leave it in the mercy of Censure to determine, whether or no we pretend to understand, What are the proper Figures and other essential Qualities of the insensible Particles of Light; with what kind of Vibration, or Evolu∣tion they are deradiated from their Fountain; What are the determinate Ordinations, Positions, and Figures of those Reflectent and Refringent

particles in the extreams of Bodies, Diaphanous and Opace, which modifie the Light into this or that species of Colour; What sort of Reflection or Refraction, whether simple or multiplyed, is required to the creation of this or that Colour; What are the praecise proportions of shadows, interwoven with Light, which disguise it into this or that colour. Besides, had we a clear and apodictical theory of all these nice••ies; yet would it be a super∣lative Difficulty for us to advance to the genuine Reasons, Why Light, in such a manner striking on the superfice of such a body, therein; suffering such a Reflection or Refraction, or both, and commixt with such a propor∣tion of shadows in the medium, should be transformed into a Vermillion, ra∣ther then a Blew, Green, or any other Colour. Again, were our Under∣standing arrived at this sublimity, yet would it come much short of the top of the mystery, and it might hazard a dangerous Vertigo in our brains to aspire to the Causes, Why by the appulse of Light so or so modified, there is caused in the Eye so fair and delightful a Sensation; as that of Vision; and why the sentient Faculty, or soul therein operating, becomes sensible not only of the particular stroak of the species, but also of the Colour of it.

For, where is that Oedipus, that can discover any Analogy betwixt the Retina Tunica, Optick Nerve, Brain, or Soul therein resident, and any one Colour? and yet no man can deny that there is some certain Analogy be∣twixt the Species and Sensory: since otherwise there could be no Patibility on the one part, nor Agency on the other.

We are not ignorant,* 1.11 that the aspiring Wit of Des Cartes hath made a towring flight at all these sublime Abstrusities, and boldly fastned the hooks of his Mechanick Principles upon them, thinking to stoop them down to the familiar view of our reason. But supposing that all Colours arise from the various proportions of the process and circumvolutions of the particles of Light in bodies respective to various Dispositions of their superficial parti∣cles, which accordingly more or less Accelerate, or Retard them; as He hath copiously declared (in Dioptric. cap. 1. & Meteor. cap. 8.): and erecting this upon his corner stone, or grand Hypothesis, that Light is nothing but an Appulse or Motion of the Aether; or most subtile, and so most agile matter in the Universe; which is meerly praecarious, and never to be conceded by any, who fears to ensnare himself in many inextricable Difficulties, In∣congruities, and Contradictions, in the deducement of it through all the Phaenomena of Light, Colours, and Vision: all that we can allow him, as to this particular, besides our thanks for his laborious Endeavours, is that close of Phaetons Epitaph, Magnis tamen excidit ausis.

Notes

• * 1.1

  Art. 1. The Nativity of White; or the reason of its percep••ion by the sight
• * 1.2

  Art. 2. Black, a meet Privation of Light.
• * 1.3

  Art. 3. The Genealo∣g•• of all Inter∣mediate Color▪
• * 1.4

  Art. 4. The Causes of the Sympathy & Antipathy of some Colours.
• * 1.5

  Art. 5. The intermi∣stion of small shadows, a∣mong the lines of Light; ab∣solutely neces∣sary to the Ge∣neration of a∣ny Intermedi∣ate Colour.
• * 1.6

  Art. 6. Two eminent PROBLEMS concerning the Generation and Transpositi∣on of the Ver∣million and Cae••ule, appin∣ged on Bodies by Prismes.
• * 1.7

  Art. 7. The Solution of the Former: with a ratio∣nal Conjecture of the Cause of the Blew, apparent in the Concave of the Hea∣vens.
• * 1.8

  Art. 8. The Solution of the Later.
• * 1.9

  Art. 9. The Reasons, why the Au∣thor proceeds not to investi∣gate the Cau∣ses of Compound Colours in Particular.
• * 1.10

  Art. 10. He confesseth the Erection of this whole Discourse, on simple Conje∣cture: and enu∣merates the Difficulties to be subdued by him, who hopes to attain an Apodictical Knowledge of the Essence & Causes of Co∣lours.
• * 1.11

  Art. 11. Des Cartes at∣tempt to dis∣solve the chief of those Diffi∣culties; unsuc∣sessful: because grounded on an unstable Hypothesis.