Chapter 23

Of Seing

THE Powers of the Sensitive Soul in speciall are Seeing, Hearing, etc:

1. Seeing, an Exterior sense perceiving visible things by the help of the Eye;1 of this consider the Organ, Object, Mean, Manner, and dignity

1. The organ, or Instrument of Seeing is the Eye; a part of the body made up of Nerves, Coates, and Humours, which are more fully handled in anotomy, yet tis need full here to take a Short notice, of its fabriek to discribe the [bulb] of the Eye, we must begin with

1. The Optiek nerve, and here a little of nerves in Generall will need to be Spoken to. Wee noted before in Chapter 19 that there are 3 sorts of vessels branched abroad throughout the whole body veines, arteries, and nerves, the former two Serve for Circulation of the blood (as was Shewn) but the nerves (besides what they contribute to the ferments, and Seperations there mentioned) have their own manifest use in sence, and motion, Some think there are different kinds of nerves for these different works, because tis observed in Palseyes, that Somtimes one power is weakened and distroyed without much prejudice of the other all these nerves have their originall from the [70] brain and Seam to be continued with it; being only a kind of propagation or protrusion thereof into Severall parts of the body; Each nerve hath two Coates, and a pith. The Coates are continued with the two Coates of the brain called Meninges and Mininxes and the Pith from the Substance of the brain it Self. Now of all these nerves the opticks are two one for Each Eye [which] coming out from severall parts of the brain they Meat and touch but not Cross, and Mingle, and then part again to go to Each Eye; [here] the Outer Coat ([or] Mininx) forms the [bulb] or ball of the Eyes; and So far as the white of the Eye goes tis Covered with another Coat (Caled adnata, or growing upon) to which the Muscles that move the Eye are fastened, and indeed do Constitute it out of their white tendons. The ball of the Eye is contained all within the Coat called Cornea, (or Horney) which is clear and transparent; and this is the first part of the Eye that the visible rayes do touch.

Organ of Sight is th’ Eye whose nerve from brain

Comes with its Horney Coat all to contain.

2. Within this Cornea, is the Uvia (or Grapelike Coat) So cal’d because tis Striped like the Skin of a Grape. If (the pulp, being Crushed out) it be Stuck against the Glass of [the] window. This is it which gives the Severall Colours (Called the rainbow of the Eye) which Colours are perceived through the Horney Coates transparency, but itself is not transparent; only in the forepart or middle it is perforated or has a hole in it which because of the Darkness within, and the Clearness of the Humours receives in light, and Colour without reflection, and therefore appears black. This hole is commonly cal’d the Window, or Pupill of the Eye through which the light has its Entrance to the farthest Side of the Eye where vision is made. The little Image or baby (as tis Cal’d) that is Seen in the Pupill by another looking on, is but a Specular reflection from the outer polite Surface of the Cornea because it has only [blackness] or darkness behind it; So any Glass that is [blackned] on the one side, is Specular ([or] a looking-Glass) on the other; and as for the littleness of this Image, it is from the Globular figure of the Eyes (as is shewn in Opticks) This hole of the Uvia (or Pupill) is contracted if the Eye be turned to the light, or look on [any] thing at a great distance, but under contrary Circumstances tis Sensibly dilated. The reason is to let in so much light as is convenient, and no more.

The rainbow of the Eyes, the Uvia; this

Is perforate; the hole, the pupill is

3. The Aqueous (or Watry) humour lyes both within, and without the Uvia, and takes up all the Space between the cornea, and the Christalline humour, (or Apple of the Eye.) Now if this watry humour be dryed up, or thickned, (like as the Glaze of an Egg boyled) it hangs as a Curtain before the pupill or window, and Commonly Sticks to the Cornea. This Mallady is called a Cataract whose Couching (or removing downwards) below the Pupill by the point of a needle in a dextrous manuall opperation piercing the Cornea on the one Side, Dos but as it were draw the Curtain from before the window and let in the light.

The watry humour thickned keeps out light,

Couching the Cataract restores the Sight.

4. The Christalline humour, (or the Apple of the Eye) lyes behind the watry, and is lodged in a bed (or hollow) of the Vitreous (or Glassy) humour which lyes behind it. This Christalline is a body of pretty Solidity, perfectly pellucid as Christall (whence it obtains its name) and boyles white, and hard (as the White of an Egg does) at least the Outer part there[of]. Hence an Over heat in the Eye may so Spoile it as that it can transmit no rayes. This desease is cal’d Gutta Serena wherein the Eye looks outwardly well, but [sees] nothing, and is thought incurable. This Christaline is Sustained by Certain filaments hardly discernable; [with one] End fastened to the Insides of the Uvia and the other ends to the body of the Christalline round about; Herby the Christalline is either drawn flattish, or permitted to rise more round on Each side, according as the Vision requires, but if by Age the Christalline be too much dryed to be thus plyable then a Supply is made by Spectacles which by their refraction So order the rayes that they may notwithstanding come in their proper pen[c]ill, and point the Object at the bottom of the Eye. These filaments are Called the Aranea (or Cobweb) of the Eye; because they Somwhat represent a Spiders web which bear up a Spider in its middle, as these fine threads do the Apple of the Eye

The Christalline or apple of the Eye

Has its Aranea to hang thereby.

5. The Vitrious (or Glassy) humour is thicker than the watry and thinner than the Christalline, about the Consistence of the Glare of an Egg, or a little more Sollid nearer to that of boyled Starch it boyles not white or hard So Soon as the Christalline: It fills all the hinder part[s] of the Eye; and has a hollow cavity in [its] forepart where the Christalline is lodged. This is transparent as the other Humours, and is Seldom much out of order only it [71] wasts with age, and this Causeth the hollowness of the Eyes.

Behind the Christalline do Vitreous lye

Which when decay’d by Age makes hollow Eye.

6. The retina (or net-Coat) which is the Expansion of the very pith of the Optick nerve in Whitish filaments; and these are like to [a] network hanging fastened to the Inmost Wall of the Eye. [Here] it is that the Species, or picture of the outward object is represented in little; and here indeed Sight is formally performed, whereas [indeed] all the other coates, and Humours do by their Severall refractions only prepare the Species, and make it apt to be Seen.

The Retina, Pith of the Optick nerve

for the prepared pictures Sight doth Serve.

Having thus Spoaken to the Severall parts of the Eye apart. We come now to put them to Gather in this diagram. Suppose (a) the pith of the Optick nerve div[ar]icating it selfe to make (e.e.) The retina where the picture is made, (b.) the Inner coat of the Nerve making the Coat Uvia (ff) which has its Iris, and hole before (G.), (C.) the outer Coat of the Nerve making the Cornea coat (K K) which at (L) puts its Self a little forwards and there the Iris dos appear through it, where the Adnata coat (M M) ends (d) the Christalline humour Sustained by its threads, the Aranea that [go] out to the Uvia every way from it having the watry humour before it as at (g) and the Vitrious behind it as at (e.e.) and thus much of the fabriek of the Organ of the Eye.

Three humours, and 4 Coats with filaments

White, pupill, Iris, all the Eyes content[s].

2. The Object visible which are light, and Colour.

1. Light or Luminous body; these are distinguished as the fountain and streames So as Luminous is the body sending forth light, (as the Sun, flame, etc:) [and] light is that which is in or on the thing enlightened (as the Air the body Shone upon). This thing that is so lightsom in itself, is most obscurely defined by Aristotle the Act of [a] perspicuous, as it is perspicuus, which (I must confess) to me is utterly unintelligable. Latter men call it particles of finest matter continually streaming every way from a Luminous body every one of the multitude of Streames is cal’d a Ray; In matter these rayes will agree with flame, only the motion of them is diverse, for the motion in flame is constipated, and circulating in a small Space and therefore making attrition whereby heat is generated and made more intence. Whereas the motion of light is streight forwards in right lines from the center of their motion whereby they get more room continually to Expatiate themselves and So to avoid attrition. [Those] rayes of light may be illustrated by a comparison to water which in a small stream or thread rushes out, and spins off at a distance through, [and] from a little hole of a pipe, or Cistern; as also (or rather as is before noted) [to that] sending forth the little streams by the twirling upon the hand of a maids wet mop whereby it [Springeth] water every way.

Visible object, light, flame every ray

In a fine matter every stream’s a way.

Now this Hypothisis is very agreable to the p[h]ainomena of sight, and Light, such as,

1. Sight is in a moment, for the mater being alwayes everywhere in the Air, there needs but a motion to be given to it by the luminous body, and presently tis communicated to all the particles that stand in the same line; like as in a long body receiving motion at one End that End immediately communicates it to the other end to avoyd penitration of dimentions for if [my] hand gives motion to the End (a) and cause it to remove to the place (b.) in the [same] moment it causes the End (c.) to move onwards towards the place (d.) Now this Simile holds even in the discontinued [Globules] of light; because the Air is so full of them that they cannot turn aside in an Eddy (as tis in Water) but are kept streight forwards by others of their own kind

2. Sight is in a [Sensibly right] line, for such is the motion from the Luminous body to the Eye; tis said (sensibly) [for] there may be an insensible [flexure] of the line; the rayes may pass one by the other when they pass from two distant lights to two distant Eyes, that is the ray of one light passing to the one Eye dos not cross the other lights ray passing to the other Eye in the very same point, for then the motion of the one or other should be broken, or two particles of matter should be in the same [space], but tis thus; the one ray passes by in the next point to the others, and this makes a little flexure, but it is so little that it is insensible, this Solves the difficulty, and takes off [72] the Argument above mentioned Concerning [sensible] Species, and spiritall accidents.

3. The Greater light obfuscates the [less], that is the Stronger motion of rayes from the more luminous body, either wholly diverts, or much disturbs the motion of rayes from the [less] or [weaker] luminous body; so that they cannot at all or not well reach the Eyes. hence the flame of a candle in bright Sunshine even disappears.

Lights in a moment in a line that’s right

the Greater overwhelmes the lesser light.

4. Shaddow is the partiall privation of light, for it is by the interposition of an opacous body which stops the motion [and] intercepts the streams of light so that they cannot come directly to illuminate a body; yet tis said to be but partiall, because some reflected rayes may com into the place where the direct ones are intercepted, and excluded, but darkness is a totall privation; because though the matter of light be there yet the motion both direct, and reflex is absent.

5. Rayes of light pass through a Diaphinous body, though a little turned aside or refracted, they pass through because the pores of the transparent or Diaphinous are streight or at least Such in figure as can transmit the moved matter continuing its motion; they are refracted because of the obstruction they meet with. The reason is for that a certain Quantity of motion being communicated to the [Globules of] light they pass on streight in the thinner and equall medium; but when they meet with a thicker, they are somwhat hindered, and though at last they break through yet upon the obstruction, the motion that [should] have otherwise spent itself in going forward, turns itself sidewise; like as an Arrow shot at a butt when the forepart begins to Stick, the hinder part is also Stoped, but this cannot present[l]y leave its velocity, and therefore Spends the remainder of its motion in vibrating its self, and Whirling. but how the passing rayes thorow the thinner and thicker medium first gives the diversity of termination and the inclination to and from the Axis is to be found more fully handled in opticks.

By partiall lights privation, Shaddows be

Refracted rayes through double mean we see.

6. Reflection of light is in the like angles; So that if the falling of a ray be at right angles (or directly) on a polite body the reflection is also direct and in the same line; but if it fall obliquely then the [reflected] Image from the pollish’t body (or looking Glass) is seen in the same obliquity; for if (a.b) is the Surface of the looking-glass then a thing placed at (d.) is seen back again in the same line at (d.) but if it be placed at (c.) then it is seen at (e.) by the Eye there placed, because the Luminous rayes in their motion are so turned back as to make the Angles of incidence and reflection of the same Quantity; Just as a ball rebounds from the Ground (upright, or [sidewise]) according as it is cast upon it.

7. Light intended burns; this is seen in the burning-Glass where all the rayes that fall on the Glass are by refraction directed unto a point They there being constipated, Rubb against Each other, and so intend the light and heat even into a flame.

Incident rayes in the like angles turnes;

Light when intended proves a flame and burns.

And thus much of light.

2. Colour (another object of Sight) is as blindly defined by Aristotle the Extremity of a perspicuous as Terminated; which also must be understood by those that can. Since the Candle of Phylosophy has been better Snuff’t, we have better light to see what Colour is. And yet indeed it must be confessed to be but candlelight; However tis more clearly Expressed than formerly by Light diversifyed, or reflections [and] refractions of light according to the figure and site of the minute Superficiall particles of the body that reflects it to the Eye. Tis therefore a Passion of Light, rather than a Quality of body; Hence it follows

1. that White and black (formerly accounted the 2 Extream Colours) are indeed no Colours at all, for

1. White is but light reflected Undiversifyed from Polite superficiall [Globules], as wee see in froth which is white whatever be the Colour of the Liquor for Every little bubble (a multitude of which makes froth) gives its Vivid reflection (or stell) from one point as all Globular Polites doe; these Stells being thick set togather appear to the Eye as one plain light, for that the darke [spaces] between the Stells do not appear unless by near approach of the Eye.

2. Black is but a privation of lights reflection; for if the Superficiall parts be accuminated (or Sharp) they drink in the rayes between them, and reflect them not at all. Thus we see any hole in the door appears black to the Eye; and Windows at a distance shew darker than the rest of the wall in which they are placed, because they drink in many of the rayes whereas the wall reflects them. Other Instances are given of Plush; Hair of [a] Dogs neck brisled up; Standing Corn in the feild Waved by the wind etc: All which reflect light or appear dark according as the flat Sides or sharp Ends are turned towards the Eye. [73] Black Horn appearing White in its Shavings, and the Change of Colour in Liquors by Certain Mixtures is done only by Altering the figures or position of the particles

Colour is Light diversifyed; Black, White,

Are none; ’tis, or ’tis not Reflected Light.

2. That all true Colours are from Reflecting, and refracting Particles therefore the body Coloured must have Somthing of Diaphainety (or Transparence) in the Superficiall parts or there Could be no refraction; Hence Die-Stuffs are of Salts, or Christalline parts, which the more polite they are the more vivid and Glossy are the Coloures; because more rayes of Light diversifyed are returned to the Eye. Nor Let any think it Strainge that the Superficiall parts of an Opaque body Should be diaphinous; for though they Appear not So to the Naked Eye, yet the Microscope will plainly discover them to be such, if you veiw them in the bright Sunshine. Now that Refractions, and Reflections make Colours is Manifest by the Prisme or Long Trigonall Glass which in Certain positions (Cross the Nose) Gives all the Colours of the Rainbow; and So Likewise Cut diamonds, and other transparent Stones from their Angular figures; Of all which se[e] Mr Boill of Colours who Gives the best account of this Matter that I Know. Therfore these Salts of Diestuffs (before Mentioned) Either are themselves figured to Give Such Diversifications of light, and then are Lodged in the pores of the Dyed body; Or Else they So alter the Superficiall parts of the body Its self as to fitt [them] for such Diversifying. And Alume is Usually added to Supply the defects of Glossines and vivid reflections.

3. There are but few Primary or Simple Colours, and others are made by their Mixtures. thus Purple is made out of red and blue; Green of Yellow, and blue, etc: And Indeed ’tis a pleasent Sight in a Microscope to descern the Distinct Graines of blue and Yellow powders Interspersed, when through the Instrument no Green at all will appear; Whereas If you Look with the Naked Eye upon the well mixed Powders you will see only Green, and no blue, or Yellow at all. And Hence it is that Green stuff or Cloath, will stain blue, by Urine or Other Acids, because the Yellow particles that Stick not So fast as the blue are by them [easily] removed. And Hence also blue Hangings, Gilded (as it were) with yellow Candle-Light alwayes appear Green. But why Yellow appears whitish by Candle-Light is a Matter to be further Enquired [of].

Refracting, and Reflecting parts give true,

and Vivid Colours, Primaries are few.

4. No Body has Colour as an Inhærent Quality therein but only as a Disposition thereunto in the figures and Positures of the parts, apt So, or So to diversify Light when it comes upon them. Hence there is no Colour in the Dark, or on the Inside of the Stick of Wax which is not red untill it be broken, and yeilds a Superficies to the Light.

5. Light may be tinged in transparency, as we may See in Coloured Glass thin China etc: because in the Passage tis diversifyed after the Same manner that it is from the Surface of other bodyes.

Colour is not Inherent Quality.

Light may be tinged in transparency.

6. Polite bodyes reflect figure, and Colour. Whereas rough ones do only Light, because Light will return any way more Easyly than the Diversifications, and Limitations thereof. And this may help to Solve the Appearance of figures and Colours by an Object Glass, at the Hole of a dark Room, for the Glass Colects the modifyed, and Limited reflections of Light, and transmits them to the paper where they are distinctly Seen; because all the Light that Comes in the Glass is So regulated: But if the Paper be removed out of its due distance, both Colour and Figure Vanish; because then the Regularity, or Lymitation is Disturbed; or if a Greater Light be Let in other Wise than through the Glass, the Light coming in Irregular mingles with the other and Spoils its regularity.

7. The old Distinction of Real, and Apparent Colours is [vain] for all Colours are alike reall or apparent, the Red in the Rainbow is as reall as the red in the Scarlet Cloth; both being but the Same kind of Modification of the Same Light.

Figure, and Colour by Polites are done

Reall, apparent Colours are but one

8. Lastly: Add to all this that though it be past all doubt that Colour is made by regular reflections [of light] yet the distinct rule of reflection, and refraction proper to Each Colour is not yet determined, Mr Boile himself recommends it, as a Matter of further Contemplation by the help of the Trigonal Glass before mentioned. And thus much of Light, and Colour the Visible objects of Sight

tho Colour be not what ’twas said (be sure)

yet Shewn by Light it Self remaines obscure

3. The Mean (or Medium) carrying the Object (or Visible species) to the Organ (or Eye) must be alwayes Somthing perspicuous, as Air, Water, Glass, etc: of this observe 3 things [74]

1. If The Medium be Single, or of Equall density, then the Object appears in the Same place and after the Same fassion.

2. But if it be double or Multiplyed; as Aire, and Glass; Aire, and Water, etc: then there is refraction; that is the Ray is Bowed, and this is after a twofold Sort.

1. Towards the Axis (or Middle Line of the Optick Cone) If the first medium be thin, and the Latter thick.

2. But If (on the Contrary) the first be thick, and the other thinn then the Refraction is from the Axis.

3. If the Surface of one of the Mediums be Convex or Concave the Refraction is also varyed according to the Rules of opticks; Where all the Nature of reflections, and Refractions are fully treated [of].

One Meane Presents a thing Just as it is

If Double, Convex, Concave varyed tis.

4. The Manner of Seeing (not as it Seams to be) by Extramission or Sending forth Rayes, or Spirits from the Eye to the Object; for the Eye is not Powerfull enough to Send out as far as [the] Eight[h] Sphere, or to the fixed Stars, and So far we can see; But by Introreception (or receiving inwards) of Lightsom rayes, Sent Originally (as from Luminous bodyes) or Reflected (as from all others) into the Eye. Therefore directing the Sight to the thing to be perceived, is but putting the Window or Pupill of the Eye directly against the Object so as to receive in its Species, to be depicted on the Retina (or bottome Coate of the Eye) whereby the Parts of the Optick Nerve are So moved, Pressed, or Affected as to Convey the Sentiment into the part of the Brain where the Common Sence is Lodged.

Intro-reception doth the Species bring

Where Nerve in Retina perceives the thing.

This doctrine of intromission Militates with that Conceit of Fascination (or Witch-Craft) by Looking upon with an Evill Eye, According to the Vulgar tradition, yet with all it must be Granted that as the whole body is Perspirable, So the Eye may have its Emissions for Some Small distance, but whether So as to affect another body, I much doubt. Wee may indeed be terryfyed with a fierce Look, and Refreshed with a Gracious, and favourable one, etc: But this Seams to be rather by Ratiocination about the Person who Shews Such a Countenance than by any Steams which proceed from the Eye. Tis as if one should say to himself; that Person looks fiercely, therefore he will hurt me etc: Certain it is that a Passion Changes the Eye, but not the beholder of that Eye, Unless by Humane Sympathy or Reason about the Consequence of that Passion.2

Fierce Looks do terrour strike Love, Greif in Eye

Work Like by Reason, or by Sympathy.

5. The Dignity of this Sence beyond the Rest, is in diverse respects, but in two Especially; Finess of Species, and Matter of Reason.

1. Its Species, (If I may so Call them) have a nearer approach to the Spirituall nature, and Active motion of the Soul; for we see allmost as soon as we think, in a moment, and at a Great distance, and that by Rayes of the Most tenuious matter; whereas all other Senses require Grosser matter nearer approach, and Longer time to perceive.

2. It also affords matter of more Rationall Contemplation; the Visible things of the Aspectible world lead us to acknowledge, and Meditate upon the Invisible things of God. ’Tis also Dignifyed with a Mathematicall Science, Namly opticks which is dependent on Sight, and is Subservient thereunto. And So Much for this first Exterior Sence of Seeing.

Sight to the Soul doth bear a Near Relation

More Matter dos afford for Contemplation