An entire body of philosophy according to the principles of the famous Renate Des Cartes in three books, (I) the institution ... (II) the history of nature ... (III) a dissertation of the want of sense and knowledge in brute animals ... / written originally in Latin by the learned Anthony Le Grand ; now carefully translated from the last corrections, alterations, and large additions of the author, never yet published ... by Richard Blome.

CHAP. XVII. Of Colours.

I. Colour is nothing else, but a Modifica∣tion of Light. FOrasmuch as Colours are the Objects of Seeing, we are to consider what they are, and wherein their Nature doth consist, before we undertake the Explication of the Sense of Seeing. We suppose therefore in the First plcae, that no Colour can appear without Light, and that conse∣quently Colours are nothing else but certain Alte∣rations or Modifications that happen to the Light. Secondly, that even Transparent Bodies also, appear distinguish'd with various Colours, if the Light that falls upon them be variously reflected to the Eye of the Beholder. As may be seen in a Round Ball of Glass fill'd with Water, in the Bubbles that Children sport themselves with, in a Prism, in the Rain-bow, and in other Bodies.

II. What Light and the Beams thereof are. We must also suppose the Light to be the Action of a Subtil matter, the Parts whereof, as so many small Pellets, do roll continually through the Pores of Earthly Bodies: So that there are innumerous Rays or strait Lines by which this Action is com∣municated, which proceed from the several Points of a Lucid Body, and reach to the several Parts of the Body which they enlighten.

III. That in∣numerable Rays pro∣ceed from every Point. For we are to conceive, that there is no surface, how polish'd and smooth soever it may appear to the Eye, but is really rough and unequal; so that every Point assignable in the outside of the most smooth Body, is to be imagined like a little Hil∣lock or Prominence, from whence innumerable Beams may be dispersed round about. For other∣wise, if the surface of any Body were altogether polish'd and smooth, it could not shed the Rays roud about, but only directly to the opposite side; so that the Object would only reflect such direct and Parallel Rays, as could only reach to the Eye obliquely or slantingly placed.

IV. The Rays of Light may be reflected after di∣vers man∣ners. Moreover we are to take notice, that tho' the Rays pass strait along through Trasparent Bodies, yet they are easily turned aside by others they meet with; much after the same manner as a Ball struck against a Wall, rebounds variously, according to the difference of the Surfaces it lights against. For it rebounds otherwise from a plain and even Surface, than from a crooked; and otherwise from a hard, than from a soft: For being struck against a soft Body, it loseth its mo∣tion; whereas lighting upon a hard, it rebounds immediately.

V. The Rays, besides their mo∣tion in right Lines, may also be moved round. Lastly, We are to take notice, that as a Ball, besides its motion whereby it tends from the Hand to the Wall in a right Line, and from thence re∣bounds elsewhere, is capable also of being moved round its own Center: So likewise the Rays of Light cannot only move to Right Lines, but may be so reverberated by the Bodies they light upon, as to take upon them a Circular motion, wholly in the same manner as a Ball struck by a Racket, re∣bounds against the floor or ground.

VI. VVhat Co∣lours are. From what hath been said, it follows, that Colours are not in the Colour'd Bodies, but are only such a disposition, which either swallows up the Rays of Light, or variously reflects them to the Eye, and according to the diversity of this motion, doth differently affect the most subtil Organs of the Sight, and by this means produce a Sense of Colours in us. So that Colours, as they are assignable to Bodies, are nothing else, but dif∣ferent Modes, according to which Bodies receive the Beams of Light, and either drown them, or with great variety reflect them to the Eye.

VII. VVherein the Nature of Colours ••oth 〈◊〉〈◊〉. Let us suppose therefore, that there are some Bodies, which when they are struck with the Beams of Light, do choak them, and break all their force; and such are those that are of a Black Colour, which is common to them, and Darkness. That there are also other Bodies that reflect the Beams, some of them in the same manner as they receive them, viz. such Bodies, whose Surface being exactly polish'd, serve for Looking-Glasses. Others, which reflect them confusedly this way and that way; and again, that amongst these some reflect these Rays so, as that the Action of Reflection is not spoiled by any the least alteration, viz. those Bodies that are of a white Colour. And that others again produce a Change like to that which happens to the motion of a Ball that is struck with a slanting Stroak of a Racket; and such are the Bodies that are of a Red, Yellow, Blue, or other Colour.

VIII. Colour is nothing else, but a Modifica∣tion of the Rays o•• Light. For when the Rays of Light are sent forth from a Lucid Body, the Globuli of the second Ele∣ment, which constitute those Rays, are either evenly or unevenly driven forwards, and whirl'd about by a different Proportion; because of the various Nature and Constitution of the Bodies they meet with. And from this proportion of their direct Motion and Circumvolution, all Modifications of Light, or Colours do proceed. This is evident in Transparent Bodies, in which many Colours do appear, whereof no other Cause can be assigned, besides those different Modes, according to which the Beams of Light are admitted. As may be seen in the Rainbow, Peacocks-Tails, and in the Necks of Doves; forasmuch as these Colours can∣not be said to be any thing else, but the Light it self received in the outward-parts, and so or so reflected and conveyed to our Eyes. For all the Particles of Light, that enter a Transparent Body, are not drowned or swallowed up of it, but many of them rebound, which by means of various Re∣flection and Refraction reaching our Eye, do pro∣duce in us the Sense of Colours.

This will appear clearly to us in the Prism MNP, 2 of the Surfaces whereof, MN, and * 1.1NP, are entirely plain or flat, and so inclined the one towards the other, as to constitute an Angle of about 30 or 40 Degrees; and therefore if the Rays of the Sun ABC, that light perpendicu∣larly upon the Surface NP, do penetrate or pierce it obliquely about the Hole DE, which exhibits a Shadow at both parts of the said Hole, to the Rays DF, and EH, passing through it; it is manifest by Experience, that the Rays passing obliquely through that Hole, from the Glass into the Air will be refracted, and reaching the Surface HGF, (which we suppose to be White) they will exhibit divers Colours from H to F, and that in this order: In the first place they will represent a Blew or Violet Colour about H; then a Green; in the 3d place, a White about G; 4thly, a Yellow; and 5thly, a Red Colour about F.

Now what happens in this Production of di∣vers Colours, but only this, that the Globuli of those Rays, which after the same manner of Incli∣nation, falling upon the lower Surface of the Prism NP, on the Left hand towards DN, have a Shadow, caused by the slow motion of the Glo∣buli of the 2d Element; whereas on the Right, towards EP, they have a Light, caused by the swift motion of the said Globuli; which causes them to move more swiftly about their own Centers, than they do in a Right Line.

For the better understanding whereof, let us suppose a Ball 1, 2, 3, 4, so struck from V to X, as * 1.2to proceed only in a right motion, and that 2 of its Sides 1 and 3, with equal swiftness fall down to the Surface of the Water YY, where the motion of the Side 3, which reacheth that Surface before the other, is retarded, that of the Side 1 being not changed at all; whereupon the whole Ball begins to roll about, according to the order of the Fi∣gures 1, 2, 3. Now this Circumrotation will be much swifter, than its progress, in case the Ball S,

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Book. 1. Part. 8. Chap. 10

Lens. Inv.

I. Kip

To the Worship∣full William Ʋpton of Lupton in the County of Devon Esq^r.

This Plate is humbly Dedicated by Richard Blome.

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Book 1. Part 8. Chap. 18.

To the Honoured S^r. Iohn Morden of Ricklemarsh in the Parish of Charleton in the County of Kent Baronet, and to Susanna his Lady. Sister to the Right Worshipfull▪ ••^r. Joseph Brand of Edwardstone in Suffolk Knight. This Plate is humbly Dedicated by Richard Blome.

The West Prospect of Morden Colledge, in the Parish of Charleton, in the County of Kent, now Erecting at the sole charge of the Honoured S^r. John Morden of Ricklemarsh in the Said Parish of Charle∣ton Baronet, who hath liberally endowed it for the Maintenance of forty decayed Merchants, in a more then vsuall manner, as well as to Dyet, and Apartments to themselves, as to their Stipents or Salaryes, for their Sup∣port in a Gentile lively hood, This being the noblest, Greatest, and most Charitablest Guist of any Subject in these three Kingdomes,—Especially in the life tyme of the Donor, to his Eternall Glory, and for the good Example of others to follow soe pious a Worke.

being moved more slowly than it, and lying be∣neath it, about the part of the Ball 3 2, chance to stop its progress; and that Ball Q, plac'd above it, about the part 4 1, being more swiftly moved, do forceably push it forwards, and by this means make its rolling about to be much more swift than its Progress. But if the Ball 1 2 3 4, falling slantingly from V, on the surface of the Water YY, towards X, and first touching it with its Point 3, do roll about slowly, according to the order of the Numbers 1 2 3 4: I say, if this suppos'd, it have on the Side 1 the Ball R, moved more slowly than it self, and thereby hindring its whirling round; and on the Side 3, it have op∣pos'd to it the Ball T, more swiftly moved than it self, it will by this its more swift motion retard the Ball 1 2 3 4, striving to whirl it self about, according to the Series of the foresaid Numbers, and so will make its Circumrotation much more slow, than its progress.

IX. Whence the difference of Colours doth arise. These things being well observed, we shall easily understand, that by how much nearer the Rays of Light, passing through the Hole DE, do approach to the Left Shadow D, by so much greater will be the whirling about of the Globuli of the 2d Element, than their Progress: Whereas the nearer they approach to the Right Shadow E, they are whirled about so much more slowly, than * 1.3they move fore-right. We understand likewise, that those Globuli which intersect the middle of that Light about G, have an Equal proportion of Retardation or Acceleration of their Circumrota∣tion and Procession. And seeing that we find the White colour represented there, we must conclude that. Whiteness consists in that Proportion: But that the Nature of the other Colours, as of Blue, Yellow, Green, Red, consists in the different swift∣ness or slowness of their whirling about, exceed∣ing that of their Process, or moving for∣wards.

X. All Colours are true Colours, and none only appa∣rent. I am not ignorant, that most Men distinguish these Colours from true ones, and call them Appa∣rent only; but these do not seem to understand the genuine Nature of Colours, which consists only in this, that they appear and are conspicuous. For it is a contradiction, that any thing should appear and be false. All Colours therefore are the effect of Light, variously reflected from the Surface of Bodies, suitable to the situation of their outside Particles, their whole difference consisting in the various Modes of receiving it, and reflecting it to our Eyes. Thus we call that a Black Body, which extinguisheth and choaks the Rays of Light; and therefore Black Bodies carry a resemblance of Darkness. Blue Colour, which approacheth to the Nature of Black, is that which reflects only a few Rays: And 'tis for this Reason, that Sea-water, where it is deep and transparent, appears of a Bluish Colour; because there are but a few Rays reflected from its Surface, and none of those that penetrate the Substance of it, do return.

XI. What a White Body is. A White Body is that, which reflects the Rays to the Eyes, in the same order as it receives them. Of this colour are all those Opake Bodies, whose Surface is so rough and rugged, that it reflects from all Sides the Rays it hath received parallel. So that in order to our having the Representation of a White Colour, we must receive many Rays from the Object; whereas for to see a Black Co∣lour, we must receive none at all. And therefore the Nature of Blackness must consist in a pro∣perty which Black Objects have, to drown and mortifie the Beams they have received, as we have mention'd before. So that we may conclude, that those are Black Bodies, whose Surface is proper to extinguish and quash the Rays of Light; and that those are White, whose Surface hath the Property to diminish the Light, by reflecting it from all sides.

XII. Wherein the diffe∣rence be∣tween Black and White Marble doth consist. But some may Object, that Black and White Marble consist, in a manner, of the same parts, so that if one of them swallows or extinguisheth the Light, the other ought to do so likewise; and consequently, that the variety of Colours is not well grounded upon the Variety of Objects, which do variously reflect the Rays of the Sun.

To which we Answer, That true it is, that Black and White Marble do, in a manner, consist of the same Parts; but yet in the Black there are some soft Parts, which by taking in or swallowing the Light, produce a Black Colour. For Black and White Marble may be compared to a Pumice-Stone, whose Pores are filled with a kind of Oily Matter, and the White to a Pumice-Stone that is only fill'd with Air. For it may easily be under∣stood, that when particles of Sand dash against this latter, they will rebound presently; but not from the former, because the Oily Matter, that fills its Pores, doth quash their motion, and in a manner swallow them.

XIII. What a Red Colour is. That is a Red Body, which in reflecting the Rays of Light, makes the Particles thereof to whirl strongly about their own Centers, in like manner as a Ball turns round by being struck against the Earth, or with the slanting stroak of a Racket. Yellow, Purple and Green Colours, pro∣ceed, as hath already been said, from this various Rotation of the Particles about their Center. So that the Particles of the Subtil Matter, that con∣stitute a Yellow colour, are more slowly whirl'd about, than those that make a Red: And those that make a Green, more slowly than those that constitute a Yellow colour: And the Purple colour is nothing else, but mixture of a Blue with a Red colour, which imparts its brightness to the former.

XIV. Colour is nothing else, but modified Light. From all which we may conclude, That Colour is nothing else, but Light Modified; for it is evi∣dent, that a Coloured Object cannot of it self affect the Sight, as being for the most part immoveable, or at least not reaching the Eye, where it is per∣ceived; neither can any thing be thought of that moves the Eye at that time, but only the Light reflected from the Body seen.

Notes

• * 1.1

  Figure 69.
• * 1.2

  Figure 70.
• * 1.3

  Figure 69.