Page:Cyclopaedia, Chambers - Volume 2.djvu/580

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on Bodies arc reflected or refracted e're they arrive at the Bodies. And adds, that they may be refracted, reflected, and inflected, all on the fame Principle, acting in different Circumftances. See Inflection, &c.

Again, Do not the Rays falling on the Bottom of the Eye ex- cite Vibrations in the Retina; which being propagated along the Fibres of the Optic Nerve into the Brain caufe Vilion? And don't feveral forts of Rays make Vibrations of feveral Bigneffes, which excite Senfations of ieveral Colours, much after the manner as the Vibrations of the Air, according to their feveral Bigneffes, excite Seniations of feveral Sounds? See Sound.

Particularly, don't the moil refrangible Rays excite the fiiorteft Vibrations to make a Senfation of a deep Violet; and the leaffc Refrangibles, the largeit, to make ajSenfation of a deep Red? And the feveral intermediate Kinds of Rays, Vibrations of in- termediate Bignefles, to make Senfations of the intermediate Co- lours ?

And may not the Harmony andDifcordof Colours arife from the Proportion or' thefc Vibrations ; as thofe of Sound depend on the Vibrations of the Air: For fome Colours, if viewed together, are agreeable, as Gold and Indigo ; others Difagreeable ? See Concord and Harmony.

Again, Have not the Rays of Light feveral Sides endued with feveral Original Properties ?

Every Ray of Light has two oppofite Sides., originally endued with a Property whereon the unufual Refraction of Ifland Cry- ital depends, and other two oppoiite Sides not endued with that Property. See Crystal.

Laftly, Are not the Rays of Light very fmall Bodies emitted from ihining Subftances ?

Such Bodies may have all the Conditions of Light ; And there is that Action and re-action between tranfparent Bodies and Light, which very much refembles the attractive Force between other Bodies. Nothing more is required for the Production of all the various Colours, and al] the Degrees of Refrangibility, but that the Rays of Light be Budiesof different Sizes; the leall of which may make Violet, the weakell and darkeft of the Colours, and be the moft eafily diverted by refracting Surfaces from its recti- linear Couric; and the reft as they are bigger and bigger, may make the itrongerand more lucid Colours, Blue, Green,, Yellow, and Red. See Violet, Red, &c.

Nor is any thing more requifite for the putting of the Rays into Fits of eafy Reflexion, and eafy Tranfmiflion, than that they be fmall Bodies, which by Attraction, or fome other Force, ex- cite Vibration in the Bodies they act upon ; which Vibrations be- ing fwifter than the Rays, overtake them fucceffivcly, and agitate them io as by Degrees to increafe and decreafe their Velocity, and thereby put them into thofe Fits. See Transmission.

Laftly, The unufual Refraction of Ifland Cryftal looks very much, as if it were perform'd by fome attractive Virtue lodg'd in certain Sides both of the Rays and the Cryftal.

Common Ray, in Opticks, is fometimes ufed for a right Line drawn from the Point of the Concourfe of the two Optical Axes, through the middle of the right Line which paffes by the Centre of the Pupil of the Eye. See Axis.

Principal Ray, in Perfpective, is the Perpendicular Diflance between the Eye, and the Vertical Plane, or Table, as fome call it. See Perspective.

Pyramid of Rays. See Pyramid.

Pentilof Rays. See Pencil.

RE, in Grammar, &c. an infeparable Particle, or Praepofiti- on, added at the beginning of Words, to vary, double, or other- wile modify and circumftance their Meaning.

The modificativei?e was Brit introduced by the Latins, from whom it is borrow'd into moft of the modern Tongues. Prif- cia7i derives it from retro, backwards; others rather derive retro from re; others derive re from the Greek fa, eafy, or from p^, I flow.

The effect of the Re is various : ufually it fignirles again, rur~ [urn, cua; as in re-joyn, re-tign, r^-fume, re-courfe, re-bound, re- cite, re-hear, re-cognize, re-compare, re-double, re-linquifh, &c.

Sometimes it Hands for contra, ****, again]} ; as in re-luctance, re-cumbent, recline, &c.

Sometimes for brig, fuper, over, as in re-dundant, fometimes for sripp'w, hnge, far as in removing, &c.

Re, in Mulick. See Note.

REACH, in the Sea Language^ the Diftance between any two Points of Land that lie in a right' Line one from ano- ther.

RE-ACTION, in Phyficks, the Action whereby a Body act- ed upon, returns the Action, by a Reciprocal one, upon the A- gent: See Action.

The Peripatetkks define Reatlion to be that which a paffive Bo- dy returns upon the Agent, by means of fome Quality con- trary to that receiv'd therefrom ; in the fame Part wherewith the Agent acted ; and at the fame time : As if Water, while it is heating by the Fire, does, at the fame time, cool the fame Fire.

It was known, even in the Schools, that there is no Action in Nature, wi hout Reaction; and it was a Maxim among them* Ornne Agms, Agendo repaiitur.

But the Equality of the Actions was not known : Sir I. Nevf ton eflabliflf d it as one of the Laws of Nature, that Action and Reatlion are equal and contrary ■ or that the mutual Actions of two Bodies ftnking one againft another, are exactly equal, but in contrary Directions; or in other Words, that by the Action and Reatlion of Bodies one on another, there are produced equal Changes in each; and thofe Changes areimprefs'd towards direct- ly contrary Parts or Ways. See Law of Nature.

Thus, whatever Body preffes or draws another, is equally prefs'd or drawn by it again : If any one prefs a Stone with his Finger, his Finger is much prefs'd by the Stone.

If a Horfe by a Rope, e^c. draw a Stone, the Horfe will be equally drawn by the Stone; for the Rope being ftretch'd both ways alike, endeavours to relax itfelf again, and by that means draws the Horie towards the Stone, and hinders the Progreffion of the Horfe, as much as it forwards that of the Stone.

If any Body ilriking againft another, doth by its Force any way change its Motion, it felf will undergo the fame Change in its own proper Motion, but towards a contrary Part; from the Reatlion of that Body, and the Equality of its mutual Preffion. 4 J

By thefe Actions are produced equal Changes, not indeed of the Velocities, but of the Motions of Bodies; (that is, of fuch Bo- dies as have no impediment any other way) for the Changes of their Velocities being made towards contrary Parts, (becaufe the Motions are equally changed) are reciprocally Proportional to the Bodies themfelves. See Motion.

Some of the School Philosophers deny any fuch thing as Re- atlioTU) properly fo call'd, at all ; urging that Action arifes only from the Ratio of the greater Inequality; that is, we are only to account for Action the Excefs of the Action, or what the A- gent does more than is returned by the Patient. But the Equali- ty between Action and Reatlion, fets alide the Exception.

READINGS, in Crkicifm. Various Readings, Varia; Lecl'tones, are the different Manners of reading the Text of Authors in an- tient Manufcripts: A Diverfity ariling from the Corruption of Time, or the Ignorance of Capitis. See Text.

A great Part of the Buhnefs of the Criricks lies in fettling the Readings, by confronting the various Readings of the feveral Ma- nufcripts, and confweiing the Agreement of the Words and Senfe.

The various Readings in the Bible and Gallic Authors, are al- mofl innumerable.

Readings arc alfo ufed for a fort of Commentary or Glofi on a Law, Text, PalTage, or the like ; to fhew the Senfe an Author takes it in, and the Application he conceives to be made of it.

RE-AFFORESTED, is where aForeft having been difaffbrefl- ed, is again made a Forefl; as theForefl of Bean was by an Act of Parliament in the 20th of King Charles II. See Forest, Af- forest, Disafforest, <&c.

RE-AGGRAVATION, in the Romt/b Ecclefiailical Law, the laft Monitory, publilhed after three Admonitions, and before the laft Excommunication. See Monitory.

E're they proceed to fulminate the laft Excommunication, they publilh an Aggravation, and Rcaggravation. Fcvret obferves, that in Prance the Miniiter is not allow'd to come to Reaggrava- tion, without the PermiiHon of the Bilhop or Official, as well as that of the Lay Judg^. See Excommunication.

REAL, Reale, is applied to a Being that actually exifts; in which Senfe it coincides with Ailual. See Actual. See alfo Reality.

Real, in Law, is oppofed to Perfonai.

Real Efiate, is that confifling in Lands, Tenements, &c. See Personal.

Real Aclion, that whereby the Plaintiff lays Title to Land, &c. See Action.

Cuftoms are fiud to be real; that is, they determine all Inhe- ritances within their Extent; and none may difpofe of them, but according to the Conditions allow'd by the Cuftoms where they are tituate.

Real Horizon. See Horizon.

Real, or Rial, or Ryal, a Spa?iiflj Silver Coin; being the eighth Part of the Piaftter or Piece of Eight. See Piaster.

The Real is equal to about Six-pence -i Sterling. See Coin.

The Silver Real is equal to 34 Silver Maravedis; the Copper Real to 34 Copper Maravedis, which only amount to 18 Silver Maravedis. See Maravedis.

There are alfo Reals of Eight, Reals of four, Reals of two, and half Reals.

The Reals of eight are the Piafters; thofe of four, half Pia- fters, i&c.

Great Quantities of Reals, or Reals of Eight, are carried into the Eaft-lndies, where they are divided into three ClafTes, and received on different Footings, viz.. the Old Real, known by the Chapelet around, whereof 100 are Current for 215 Roupias.; the fecojid, known by the largenefs of its Beads, Current at2i2i Roupias for 100; and the new at 208 4- Roupias for 100 Reals. See Roupia.

The Word in the Original Spanijh, Reale, fignifies Royal. RE ALGAL, or Risalgal, a Mineral; a kind of red Arfe- nic differing from the common Arfenic, which is white; and 11 M from