Page:Cyclopaedia, Chambers - Volume 2.djvu/595

 REF

(978)

REF

&*. From the fame Point of a Speculum. feveralRays cannot be repcled to the fame Poinr ; for in that Cafe all the feveral Angles of Repclion would be equal to the fame Angle of Inci- dence ; which is abfurd.

3°. One Ray as AB cannot be refktledio two or more Points; for in that Cafe all its Angles of Repclion would be equal to the fame Angle of Incidence ; which is as abfurd as before. See Ra- diant.

II. Each Point of a Speculum repels Rajs falling on it, from each Part of an ObjeS.

Hence, lince feveral Rays coming from feveral Parts of a ra- diant Object, cannot be rege&ed from the fame Point of a Spe- culum to the lame Point; the Rays that flow from different Points of the Objed, are feparate after Repclion: And hence each Ray fhews the Point whence it proceeded. See Vision.

On this Principle it is that the Rays replied from Mirrours or Looking-Glaffes, exhibit the Appearances of Objects placed be- fore them. See Looking-Glass.

And hence we eahly conceive why rough Bodies exhibit no Images; in regard they reflect the Light in fuch Manner as to confound Rays which proceed from different Points, by means of their Eminences and Cavities, their alternate Rifings and Fal- lings.— But for this, ail hard Bodies would be Mirrors.

III. If the EyeC, and the radiant Point A change Places ; the Point will continue to radiate upon the Eye, in the fame Courfe or Path as before.

For it the Object be removed from A to C, it will ftill radi- ate on its former Point of Reflexion B ; but there can be but one right Line drawn between the two Points G and D ; and the Rays are right Lines. Theretore that which was before the Ray of Rcpxion, will now be the Ray of Incidence; and fince it will be repcled under the lame Angle as that under which it fell, that which was beiore the Ray of Incidence, will, now be the Ray of Reflexion. So that the Object removed to C, will radi- ate on the Lye placed in A, by the right Lines CB and BA. g. e. d.

Hence, an Object is feen by the rcpfiedRay AB, with the Eye placed in A, the fame, as if the Eye were in AC, and the Ob- ject in A.

The Truth of this Theorem is Co eafily confirm'd by Experi- ment, that fome, with Euclid, affume it as a Principle; and demonftrate the great Law of Repclion therefrom. — Thus : Sup- pofe the Angle of Incidence a little greater than the Angle of Re- pclion; then will the Angle ABF be greater than that CBE. Wherefore, changing the Places of the Eye and the Object, the Angle CBE will become the Angle of Incidence; and therefore CBE greater than ABF, by the Suppofitiou. So that the fame Angle ABF will be both greater and fmaller than the other CBE ; which being abfurd, ABE cannot be greater than CBE. — The fame Abfurdity will follow, if you fuppofe the Angle of Incidence lefs than the Angle of Repclion. — Since then the Angle of Incidence can neither be greater nor lefs than that of Repclion, it muft be equal to it.

IV. The Plane of Refleclimi, that is, the Plane wherein the In- cident and reflected Ray are found, is perpendicular to the Surface of the Speculum ; and in fpherical Specula paffes through the Centre.

Hence the Cathetus both of Incidence and Repxion is in the Plane of Repclion.

That the Plane of Repclion is perpendicular to the Speculum, is af- fum'd by Euclid, Alhascon, and others, as a Principle, without any Demonflration ; as being evident from all Observation and Experiment.

IV. The Image of an Objecl feen in a Mirror, is in the Cathetus of Incidence.

This the Antients affumed as a Principle: And, hence, fince the Image is certainly in the repcled Ray, they infer'd it muft ap- pear in the Point of Concourfe of the repcled Ray with the Ca- thetus of Incidence; which indeed holds univerfally in plane and ipherical Mirrors, and ufuaily in concave ones; a few Cafes only excepted, as is fhewn by Kepler.

For the particular Laws of Reflection, arifing from the Cir~ cumpances of the feveral Kinds of Specula, or Mirrors, Plane, Con-, cave, Convex, &c. fee .them laid down under the Article Mir- ror.

Reflection of the Moon, is a Term ufed by fome Authors, for what we otherwife call her Variation ; being the third Inequa- lity in her Motion, whereby her true Place out of the Quadra- tures, differs from her Place twice equated. See Moon.

Reflection is alfo uied in the Copernican Syftem, for the Diftance of the Pole from the Horizon of the Disk; which is the fame thing as the Sun's Declination in the Ptolemaick Syftem. See Declination.

Reflection is alfo figuratively ufed for an Operation of the Mind, whereby, turning as it were back upon it felf, it makes it felf and its own Operations its Objed ; and confiders or con- templates the Manner, Order, and Laws, which it obferves in Perceiving, Reafoning, Willing, Judging, Doubting, Believing, dre. and frames it felf new Ideas of the Relations difcover'd there- in. See Soul, Faculty, Perception, Idea, &c.

REFLEX, Reflect, in Painting, is underftood of thofe Places in a Picture which are fuppofed to be illumined byaLight repcled from fome other Body reprefented in the fame Piece. See Light.

Or Repxes may be defined thofe Places which befide the ge- neral Light that illumines the whole Piece, receive fbme particu- lar Light, from their Situation with refpect to fome more illu- mined poliihed Body that refleds Part of the Rays it receives upon them. See Colour.

Repxes ate Icarce fenfible except in the fhadowed Parts.— The Management of the Reflexes requires a world of Accuracy and Skill.— All reflected Light is fuppofed to carry with it Part of the Colour of the Body which rijfLds it; fo that thofe Places which receive this Light, muft have their Colours mix'd or tinged with that Colour. But the fame Place may receive Re- pxes from different Objeds, differently colour'd, and thofe again receive Repxes from others.— The Painter therefore muft have a View to every Circumftance of the Colour, Light and Pofition of each Figure ; muft confider what effed each has on other, and purfue Nature through all the Variety of Mixtures. See Clair- Obfcure.

Reflex Vifion, or Reflected Vifion, is that performed by means of Rays refleded from the polifli'd Surfaces of Objeds to the Eye. See Vision and Reflection. t

Reflex Vipn is the Subject of Catoptricks. See Catop- tricks.

Under Repx Vifion come all the Phenomena of Specula or Mirrors of ail Kinds. See Mirror.

REFLEXIBILITY" of the Rajs of Light, is that Property whereby they are difpofed to be repcled. See Reflection.

Or it is their Difpolition to be turned back in the fame Me- dium, from any other Medium on whofe Surface they fall.

Hence thofe Rays are faid to be more ox lefs Repxible, which are returned back more or lefs eafily under the fame Incidence. See Ray.

Thus if Light pafs out of Glafs into Air, and by being incli- ned more and more to the common Surface of the Glafs into Air, begins at length to be totally reflected by that Surface ; thofe Sorts of P*ays which at like Incidences are refleded moft copi- oufly ; or the Rays which by inclining begin fooneft to be totady reflected, are moft Repxible.

That the Rays of Light are endued with different Degrees of Repxibilitj, was firft difcovered by Sir lfaac Newton ; and is fhewn by the following Experiment.— Applying a Prifm DFE, (Tab. Opticis, Fig. 55.) whofe Angles are each 45. to the Aper- ture C of a darkened Room, in fuch manner as that the Light is refleded from the Bafe in G : The Violet Rays are feen firft refleded in HG; the other Ray continuing ftill rcfraded in IK. —After the Violet, the Blue are all refraded, then the Green, &c. See Prism.

Hence it appears, that the differently colour'd Rays, differ in Degree of Repxibilitj. See Colour.

From other Experiments it appears, that thofe Rays which are moft repxible, are alfo moft refrangible. See Refrangi- bility.

REFLUX of the Sea, the Ebbing of the Water; or its return from the Shore. See Ebb.

It is thus call'd, as being the oppofite Motion to the Flood, or Flux. See Flux and Tide.

REFORM, a Re-eftablifhment or Revival of a former neg- leded Difcipline; or a Correction of reigniug Abufes. See Re- formation.

The Term is much ufed in a Monadic Senfe, for the reducing an Order or Congregation of Religious to the antient Severity of the Rule, from which it had gradually fwerved; or even for the improving on the antient Rule and Inftitution it felf, and volun- tarily making it more ievere. See Order and Religious.

In the like Senfe the Order of St. Bernard is faid to be only a Reform of that of St. Benediff. See Bernardine and Bene- dicts.

To Reform, in a military Senfe, is to reduce a Company, Regiment, or other Body of Men, either by disbanding the whole, or only breaking a Part, and retaining the reft; orfometimes by incorporating them in other Regiments.

Hence Reformado, a Reformed Officer, or one whofe Troop or Company is fupprefs'd in a Reform, and he continued either in whole or half Pay, doing Duty in the Regiment.

A Reformed Captain on Foot follows the Company, and affifts the Handing Officer as a fecond ; but ftill maintains his Degree and Precedence. See Captain.

REFORMATION, the AS of Reforming, or Correding an Error, or Abufe in Religion, Difcipline, (ire.

The Reformation of the Roman Calendar by Pope Gregorj, was effeded in the Year 1582. chiefly by theAdvice of Ahjfius Li- lius, and Clavius, See Calendar.

The Reformation of Religion, called by Way of Eminence, the Reformation, was begun by the Eledor of Saxmj, at the Sollici- tation of Luther, about the middle of the fixteenth Century. See Lutheranism.

King Henrj VIII. of England, happening to have then a Pique againft Pope Clement VII. by reafon of his pcrfifting in not al- lowing of his Divorce from Queen Catherine of Aufria, fell in with the Torrent, abolifhed the Pope's Supremacy, feiz'd the Monafteries, and other ReligiousHoufcs; and divided their Lands among the Nobility and Gentry.

In