In this fallen state of man religion begins with repentance and conversion, the two opposite terms of which are God and sin.

Tillotson.

They who never tried the experiment of a holy life, measure the laws of God not by their intrinsical goodness, but by the reluctancy and opposition which they find in their own hearts. Id.

I thro' the seas pursued their exiled race, Engaged the heavens, opposed the stormy main; But billows roared and tempests raged in vain. Dryden.

The knight whom fate or happy chance
Shall grace his arms so far in equal fight,
From out the bars to force his opposite,

The prize of valour and of love shall gain. Id. Nothing of a foreign nature, like the trifling novels by which the reader is misled into another sort of pleasure, opposite to that which is designed in an epick poem.

Id.

He considers Lausus, rescuing his father at the hazard of his own life, as an image of himself when he took Anchises on his shoulders, and bore him safe through the rage of the fire and the opposition of his Id. Dufresnoy.

enemies.

The lesser pair are joined edge to edge, but not oppositely with their points downward, but upward. Grew.

If all men are not naturally equal, I am sure all slaves are, and then I may, without presumption, oppose my single opinion to his. Locke.

Particles of speech have divers, and sometimes almost opposite significations.

Id.

Reason can never permit the mind to reject a greater evidence to embrace what is less evident, nor allow it to entertain probability in opposition to knowledge and certainty. Id.

The use of language and custom of speech, in all authors I have met with, has gone upon this rule or maxim, that exclusive terms are always to be understood in opposition only to what they are opposed to, and not in opposition to what they are not opposed to. Waterland.

A hardy modern chief,

A bold opposer of divine belief, Blackmore. This is a prospect very uneasy to the lusts and passions, and opposite to the strongest desires of flesh and blood. Rogers.

I do not see how the ministers could have continued in their stations, if their opposers had agreed about the methods by which they should be ruined. Swift. The subject of difference in political principles was introduced. Johnson. It is much increased by opposition. There was a violent Whig with whom I used to contend with great eagerness. After his death I felt my Toryism much abated.

Boswell's Tour. The emphatic speaker dearly loves to' oppose, In contact inconvenient, nose to nose, As if the gnomon on his neighbour's phiz, Touched with a magnet had attracted his. Couper.

Children, piqued instead of being convinced, hunt only for arguments in their own favour, and are mortified when a good reason is brought on the opposite side of the question. Edgeworth.

If an administration should succeed him, under which wisdom and prudence produced their usual effects of security and quiet, the right honourable gentleman would be at the head of the most violent and clamorous opposition that that country ever wit

nessed.

Sheridan.

OPPOSITION, in British politics, is collectively used for the minority in parliament, or that body

To

of members in both houses who oppose the measures of ministry. OPPRESS', v. a. OPPRESSION, n. s. OPPRESSIVE, adj. OPPRESSOR, n. s.

Latin oppressus. crush by severity; overpower; subdue: oppression is, the art or habit of such severity or eruelty; or the state of suffering it; hence misery; hardship of any kind ; and the dulness of spirit it produces; the adjective and second noun substantive corresponding.

If thou seest the oppressions of the poor marvel not at the matter, for he that is higher than the highest regardeth. Eccles. Israel and Judah were oppressed together, and all that took them captives held them fast; they refused to let them go.

Jeremiah.

I from oppressors did the poor defend, The fatherless, and such as had no friend.

When nature, being opprest, commands the mind To suffer with the body. Shakspeare. King Lear. Famine is in thy cheeks;

Need and oppression stare within thine eyes, Contempt and beggary hang upon thy back. Shakspeare. Cæsar himself has work, and our oppression Exceeds what we expected.

Id. Antony and Cleopatra. The cries of orphans, and the' oppressor's rage, Had reached the stars.

ture.

Dryden.
Alicia, reach thy friendly arm,
And help me to support thy feeble frame,
That nodding totters with oppressive woe,
And sinks beneath its load.

Rowe's Jane Shore. We are all subject to the same accidents; and, when we see any under any particular oppression, we should look upon it as the common lot of human naAddison. Drowsiness, oppression, heaviness, and lassitude, are signs of a too plentiful meal. Arbuthnot." To ease the soul of one oppressive weight, This quits an empire, that embroils a state. Pope.

Alas! a mortal most opprest of those
Whom fate has loaded with a weight of woes.

Id.

Come! by whatever sacred name disguised, Oppression, come! and in thy works rejoice! See nature's richest plains to putrid fens Turned by thy fury. From their cheerful bounds, See razed the' enlivening village, farm and seat.

OPS, in mythology, the daughter of Calus and Terra, the sister and wife of Saturn, and mother of Jupiter, Neptune, and Pluto, &c. She is also called CYBELE, RHEA, BONA DEA, MAGNA MATER, TELLUS, THYA, &c. See these articles. Lempriere confounds her with Juno, Proserpina, and even Minerva; but the mythology of the ancient Greeks and Romans is a sufficient mass of confusion and inconsistency, without confounding the mother with her daughters and grand-daughters. Her festivals were the Opalia.

OPTABLE, adj. Lat. optabilis. Desirable: OP'TATIVE. optative, expressive of de

For the ecclesiastical laws of this land we are led by a great reason to observe, and ye be by no necessity bound to oppugn them.

Hooker.

Take but degree away, untune that string,
And hark what discord follows, each thing meets
In mere oppugnancy.

Shakspeare. Troilus and Cressida. The ingredients reclude oppilations, mundify the blood, and oppugn putrefaction. Harvey. They said the manner of their impeachment they could not but conceive did oppugn the rights of par

liament.

Clarendon.

If nothing can oppugn his love, And virtue envious ways can prove, What cannot he confide to do

That brings both love and virtue too?

Hudibras.

The verb undergoes in Greek a different formation to signify wishing, which is called the optative mood. Clarke.

The OPTATIVE MOOD, in the Greek grammar, is that which serves to express an ardent desire or wish for something. In most languages, except the Greek, the optative is only expressed by prefixing to the subjunctive an adverb of wishing; as utinam, in Latin.

OPTATUS, bishop of Melevia, a town of Numidia, in Africa, flourished in the fourth century, under Valentinian and Valens. He wrote a book on the Schism of the Donatists, about A. D. 370, against Parmenian, bishop of that sect, which was published by Du Pin at Paris, in fol. 1700. He also wrote The Sacred Geography of Africa. He died A.D. 384.

OPTIC, adj. & n. s. Fr. optique; Gr. OnOPTICAL, adj. τικός. Visual; producOPTICIAN, n. s. ing or relating to vision; OP'TICS. the organ, or an instrument, of sight: optical is relating to vision, or to the science of optics: optician, one skilled in that science, or a maker of optical instruments: optics, the science of vision. See below.

Where our master handleth the contractions of pillars, we have an optick rule, that the higher they are, the less should be always their diminution aloft, because the eye itself doth contract all objects, according to the distance. Wotton.

1. OPTICS, as a science, dates its origin but little prior to the time of Alhazen, an Arabian philosopher of the twelfth century; and it may with truth be remarked that almost every thing useful in the science has originated within the last 500 years. The reflection of the rays of light is, indeed, an occurrence too frequent and too obvious to have escaped the notice of the earliest observers: a river or a fountain was the first mirror: its effect was easily imitated by specula of metal; and, as soon as any philosophical attention was paid to the phenomenon, it was easy to collect the equality of the angles of incidence and reflection; but, although it was well known that an oar, partially immersed in water, no longer appeared straight, it was long before any attempts were made to ascertain the relation between the angles of coincidence and refrac

tion.

2. Some very important facts illustrative of the nature of LIGHT will be found under that article, and we may now proceed to a brief historical outline of the science.

3. Empedocles is perhaps the first person on record that wrote systematically on light. He maintained that it consisted of particles projected from luminous bodies, and that vision was per

formed both by the effect of these particles on the eye, and by means of a visual influence, emitted by the eye itself. Both of these doctrines were combated by Aristotle, who thought it absurd to suppose that a visual influence should be emitted by the eye, and that it should not enable us to see in the dark; and who considered it as more probable that light consisted in an impulse, propagated through a continuous medium, than in an emanation of distinct particles. Light, he says, is the action of a transparent substance; and, if there were absolutely no medium between the eye and any visible object, it would be absolutely impossible that we should see it.

4. It is said that Archimedes made a compound burning mirror, of sufficient power to set on fire the Roman ships: in this form the story is scarcely probable, although the possibility of burning an object at a great distance by a collection of plane mirrors has been sufficiently shown by the experiments of Buffon. It is, however, not unlikely that Archimedes was acquainted with the properties of reflecting surfaces, and that he confirmed his theories by some experimental investigations. The work on catoptrics, attributed to Euclid, contains the determination of the effects of reflecting surfaces of different forms; but it is not supposed to be genuine. The existence and the magnitude of the atmospheric refraction were well known to Ptolemy, and a treatise of this astronomer on the subject is still extant in MS.

5. The mathematical theory of optics, or the science of dioptrics and catoptrics made some advances in the middle ages from the labors o. Alhazen and Vitellio. Alhazen was mistaken in some of his propositions respecting refraction; Vitellio, a native of Poland, gave a more direct theory of this subject, and constructed a table of refractive densities, showing the supposed proportions of the angles of incidence and refraction in the respective mediums.

6. The invention of the magic lantern is attributed to Roger Bacon, and the lens was soon afterwards commonly applied to the assistance of defective sight. It has been much disputed whether or not Bacon was acquainted with telescopes; the prevalent opinion is, that the passages which have been alleged to prove it are insufficient for the purpose; but there is reason to suspect, from the testimony of Recorde, who wrote in 1551, not only that Bacon had actually invented a telescope, but that Recorde himself knew something of its construction. Digges, also, in a work published in 1571, has a passage of a similar nature; and, from Bacon's own words, it has been conjectured that an instrument resembling a telescope was even of much higher antiquity. But the first person who is certainly known to have made a telescope is Jansen, a Dutchman, whose son, by accident, placing a concave and a convex spectacle glass at a little distance from each other, observed the increased apparent mag

nitude of an object seen through them; the father upon this fixed two such glasses in a tube a few inches long, and sold the instrument in this form. He also made some telescopes of greater powers, and one of his family discovered a satellite of Jupiter with them. Galileo had heard of the instrument, but had not been informed of the particulars of its construction; he re-invented it in 1609, and, the following year, rediscovered also the satellite which Jansen had seen a little before.

7. It was, however, Kepler that first reduced the theory of the telescope to its true principles; he laid down the common rules for finding the focal lengths of simple lenses of glass; he showed how to determine the magnifying power of the telescope, and pointed out the construction of the simple astronomical telescope, which is more convenient for accurate observations than the Galilean telescope, since the micrometer may be more easily applied to it; a third glass, for recovering the erect position of the object, was afterwards added by Scheiner, and a fourth, for increasing the field of view, by Rheita. Kepler made also some good experiments on the nature of colored bodies, and showed the inverted situation of the image formed on the retina of the eye. Maurolycus of Messina had demonstrated, in 1575, that the pencils of light are brought to focal points on the retina; Kepler's observations were thirty or forty years later.

8. The next great step in optics was made by De Dominis, who in 1611 first explained the cause of the interior or primary rainbow, and this was soon followed by a still more important discovery respecting the nature of refraction, first made by Snellius, who ascertained, about 1621, that the sines of the angles of incidence and refraction are always in the same proportion to each other at the same surface; he died, however, in 1626, without having made his discovery public. Descartes is generally supposed to have seen Snellius's papers, although he published this law of refraction without acknowledging to whom he was indebted for it. Descartes also explained the formation of the secondary rainbow, and truly determined the angular magnitude of both the bows from mathematical principles; he did not, however, give a sufficient reason for the production of colors in either case. Descartes imagined light to consist in motion, or rather pressure, transmitted instantaneously through a medium infinitely elastic, aud colors he attributed to a rotatory motion of the particles of this medium. He supposed that light passed more rapidly through a denser medium than through a rarer; other philosophers about the same time maintained a contrary opinion, without deciding with respect to any general theory of light: thus Fernat and Leibnitz deduced, on this supposition, the path of refracted light from the natural tendency of every body to attain its end by the shortest possible way; and Barrow derived the same law, in a more geometrical manner, from a similar hypothesis respecting the velocity of light, by considering a pencil of light as a collection of collateral rays influencing each other's motions. We are indebted to this learned mathematician for the first accurate investigation of the properVOL. XVI.

ties of refracting and reflecting surfaces and for the most general determination of the situations of focal points.

9. The industrious Mr. Boyle had noticed with attention the phosphorescence of diamonds, the colors produced by the effect of scratches on the surfaces of polished metals, and the diversified tints which a bubble or a film of soapy water usually assume. His assistant, Dr. Hooke, investigated these and other similar appearances with still greater accuracy, and proposed, in his Micrographia, which was published in 1665, a theory of light considerably resembling that of Descartes: he supposes that light is an impulse propagated through a medium highly, but not infinitely, elastic; that refraction is produced by the readier transmission of light through the denser medium, and that difference of color consists from the law of the different impulse constituting colored light, so that red and blue differ from each other in the same manner as the sound of a violin and of a flute. He explained the colors of thin plates from the interference of two such impulses partially reflected from the upper and under surface; but the hypothesis which he assumed, respecting the nature of colors, renders this explanation wholly inadequate; nor were the phenomena at that time sufficiently investigated for a complete solution of the difficulties attending them.

10. It was still believed that every refraction. actually produced color, instead of separating the colors already existing in white light; but in the year 1666 Newton first made the importe t discovery of the actual existence of colors of all kinds in white light, which he showed to be no other than a compound of all possible colors, mixed in certain proportions with each other, and capable of being separated by refraction of any kind.

11. About the same time that Newton was making his earliest experiments on refraction, Grimaldi's Treatise on Light appeared; it contained many interesting experiments and ingenious remarks on the effects of diffraction, which is the name that he gave to the spreading of light in every direction upon its admission into a dark chamber, and on the colors which usually accompany these effects. He had even observed that in some instances the light of one pencil tended to extinguish that of another, but he had not ascertained in what cases and according to what laws such an interference must be expected.

12. The discoveries of Newton were not received without some controversy either at home or abroad; the essential points of his theory were, however, soon established; but Dr. Hooke very warmly opposed the hypothesis which Newton had suggested respecting the nature and propagation of light. On this subject Newton professed himself by no means tenacious; he was not, however, convinced by Dr. Hooke, and disliked the dispute so much that he deferred the publication of his treatise on optics till after Hooke's death in 1703. Very soon after his first communication to the Royal Society, in 1672, he had sent them a description of his reflecting telescope, which was perhaps the first that had been constructed with success; although