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Recruits their lives in the service, or who are disabled by age or RECTORY is sometimes used for the rector's mansion Rectory wounds. or parsonage-house.

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Rectory.

RECTANGLE, in Geometry, the same with a rightangled parallelogram. See GEOMETRY.

RECTIFICATION, in Chemistry, is nothing but the repetition of a distillation or sublimation several times, in order to render the substance purer, finer, and freer from aqueous and earthy parts.

RECTIFICATION, in Geometry, is the method of finding a right line equal to a curve. The rectification of curves is a branch belonging to the higher geometry, in which the use of the inverse method of fluxions is of singular utility.

RECTIFICATION of Spirits. See DISTILLATION. RECTIFIER, in Navigation, an instrument consisting of two parts, which are two circles, either laid one upon, or let into the other, and so fastened together in their centres, that they represent two compasses, one fixed, the other moveable: each of them divided into the 32 points of the compass, and 360°, and numbered both ways, from the north and the south, ending at the east and west, in 90o.

The fixed compass represents the horizon, in which the north and all the other points of the compass are fixed and immoveable.

The moveable compass represents the mariner's compass; in which the north and all other points are liable to variation.

In the centre of the moveable compass is fastened a silk thread, long enough to reach the outside of the fixed compass. But if the instrument be made of wood, there is an index instead of the thread.

Its use is to find the variation of the compass, to rectify the course at sea; having the amplitude or azimuth given.

RECTIFYING the GLOBE. See GEOGRAPHY In

dex.

RECTILINEAR, in Geometry, right-lined; thus figures whose perimeter consists of right lines, are said to be rectilinear.

RECTITUDE, in Philosophy, refers either to the act of judging or of willing; and therefore whatever comes under the denomination of rectitude, is either what is true or what is good, these being the only objects about which the mind exercises its two faculties of judging and willing.

Moral rectitude, or uprightness, is the choosing and pursuing those things which the mind, upon due inquiry and attention, clearly perceives to be good; and avoiding those that are evil. See MORAL Philosophy.

RECTOR, a term applied to several persons whose offices are very different as, 1. The rector of a parish is a clergyman that has the charge and cure of a parish, and possesses all the tithes, &c. 2. The same name is also given to the chief elective officer in several foreign universities, particularly in that of Paris, and also in those of Scotland. It is also applied to the bead master of large schools in Scotland, as in the high school of Edinburgh. 3. Rector is also used in several convents for the superior officer who governs the house: and the Jesuits give this name to the superiors of such of their houses as are either seminaries or colleges. RECTORY, a parish-church, parsonage, or spiritual diving, with all its rights, tithes, and glebes.

RECTUM, in Anatomy, the third and last of the Red Sea large intestines or guts. See Anatomy, N° 93.

RECTUS, in Anatomy, a name common to several pairs of muscles, so called on account of the straightness of their fibres.

RECUPERATORES, among the Romans, were commissioners appointed to take cognizance of private matters in dispute, between the subjects of the state and foreigners, and to take care that the former had justice done them. It came at last to be used for com missionere, to whom the prætor referred the determination of any affair between one subject and another.

RECURRENTS, in Anatomy, a name given to several large branches of nerves sent out by the par vagum from the upper part of the thorax to the larynx.

RECURVIROSTRA, a genus of birds belonging to the order of grallæ of Linnæus, and that of palmipedes of Pennant and Latham. See ORNITHOLOGY Index.

RECUSANTS, such persons as acknowledge the pope to be the supreme head of the church, and refuse to acknowledge the king's supremacy; who are hence called Popish recusants. The penal laws against Papists are now abolished in Britain and in Ireland; and in all probability they will quickly be allowed the amplest privileges.

RED, one of the colours called simple or primary: being one of the shades into which the light naturally divides itself when refracted through a prism. See CHROMATICS.

RED, in Dyeing, see that article.-Some reckon six kinds or casts of red, viz. scarlet-red, crimson-red, madder-red, half-grain red, lively orange-red, and scarlet of cochineal but it is easy to see that there can be but one proper species of red; namely, the reflection of the light exactly in such a manner as it is refracted by the prism; all other shades being adulterations of that pure colour, with yellow, brown, &c.

RED, in Heraldry. See GULES.

RED-Bird. See MUSCICAPA, ORNITHOLOGY Index.
RED-Breast. See MOTACILLA, ORNITHOLOGY In-.

dex.

RED-Book of the exchequer, an ancient record or manuscript volume, in the keeping of the king's remembrancer, containing divers miscellany treatises relating to the times before the conquest.

RED-Lead. See CHEMISTRY Index.

RED-Precipitate of Mercury. See CHEMISTRY Index. RED Russia, or Little Russia, a province of Poland, bounded on the west by Upper Poland, on the north by Lithuania, on the east by Little Tartary, and on the south by Moldavia, Transylvania, and a part of Hungary. It comprehends Russia properly so called, Volhynia, and Podolia. It is about 65 miles in length, and from 150 to 250 in breadth. It consists chiefly of large fields, but little cultivated on account of the frequent inroads of the Tartars, and because there is no water carriage. It had the name of Red Russia, from the colour of the hair of its inhabitants. The western part is now subject to Austria, the east to Russia.

RED Sea, or Arabic Gulf, so much celebrated in s3cred

Red Sea. cred history, separates Arabia from Upper Ethiopia like spears, while on the east side, every rock becomes Red Sea. and part of Egypt. This sea is 350 leagues in length an island, and every two or three islands become an and 40 in breadth. As no river falls into it of suffi- harbour. On the ends of the principal of these harcient force to counteract the influence of the tide, it is bours the people have piled up great heaps of stones more affected by the motions of the great ocean than to serve as signals: " and it is in these (says Mr Bruce) any of the inland seas nearly in the same latitude. It that the large vessels from Cairo to Jidda, equal in size is not much exposed to tempests: the winds usually to our large 74 gun ships (but from the cisterns of mablow from north to south, and being periodical, like son-work built within for holding water, I suppose the monsoons of India, invariably determine the season double their weight), after navigating their portion of of sailing into or out of this sea. It is divided into two the channel in the day-time, come safely and quietly to gulfs; that to the east was called the Elanitic gulf, at four o'clock in the afternoon; and in these little harfrom the city Elana at the north end of it; and that bours pass the night, to sail into the channel again next to the west the Heroopolitic, from the city of Heroopo- morning." lis; the former of which belongs to Arabia, and the latter to Egypt.

Mr Bruce has made many observations on this sea, which are worthy of notice.-With regard to the name, he says it was certainly derived from Edom or Esau the son of Jacob; though in another place he says, he wonders that writers have not rather supposed it to have got the epithet of Red, from the colour of the sand on its coasts, than for other reasons they have alleged. With regard to any redness in the water itself, or in the bottom, which some have asserted, our traveller assures us that there is no such thing. It is more difficult to assign a reason for the Hebrew name of it, which signifies the Sea of Weeds; as he never saw a weed throughout the whole extent of it. "Indeed, (says he) upon the slightest consideration, it will occur to any one, that a narrow gulf, under the immediate influence of the monsoons, blowing from contrary points six months each year, would have too much agitation to produce such vegetables, seldom found but in stagnant waters, and seldom, if ever, found in salt ones. My opinion then is, that it is from the large trees or plants of white coral, spread everywhere over the bottom of the Red sea, perfectly in imitation of plants on land, that the sea has obtained this name.-I saw one of these, which, from a root nearly central, threw out ramifications of an almost circular form, measuring 26 feet every way."

Our author has also made many useful observations on the navigation of this sea. "All the western shore (he says) is bold, and has more depth of water than the east; but on this side there is neither anchoring ground nor shoals. It is rocky, with a considerable depth of water everywhere; and there are a number of sunken rocks, which, though not visible, are sufficiently near the surface to destroy a large ship." The cause of this, in Mr Bruce's opinion, is, that the mountains on the side of Abyssinia and Egypt are all of hard stone, porphyry, many different kinds of marble, granite, alabaster, and basaltes. These being all composed of solid materials, therefore, can part with very little dust or sand, which might otherwise be blown from them into the sea. On the opposite coast, viz. that of Hejaz and Tahamah, on the Arabian side, the whole consists of moving sands; a large quantity of which is blown from the south-east by the dry winter monsoons; which being lodged among the rocks on that side, and confined there by the north-east or summer monsoon, which is in a contrary direction, hinders them from coming over to the Egyptian side. Hence the western coast is full of sunk rocks for want of sand to cover them, with which they would otherwise become islands. They are naked and bare all round, with sharp points

The western channel of the Red sea was chosen, in the days of the Ptolemies, for the track of the Indian and African commerce. These monarchs erected a great number of cities all along the western coast; and notwithstanding the dangers of the navigation, we do not hear that it was ever abandoned on account of them.

From the observations made by our author on the navigation of the Red sea, he undertakes to point out a safe passage for large ships to the gulf of Suez, so that they may be able to judge of the propriety of their own course themselves, without trusting implicitly to the pilots they meet with, who are often very ignorant of their profession. This sea, according to Mr Bruce, may be divided into four parts, of which the channel occupies two, till near the latitude of 26°, or that of Cosseir. On the west it is deep water, with many rocks; and on the east it is full of islands, as has been already mentioned. Between these islands there are channels and harbours of deep water, where ships may be protected in any wind; but a pilot is necessary in sailing among these from Mocha to Suez, and the voyage besides can be continued only during part of the day. Ships bound to Suez without the consent of the sheriffe of Mecca, that is, without any intention of selling their cargo at Jidda, or paying custom there, ought to take in their fresh water at Mocha, or if there be any reason against this, a few hours will carry them to Azab or Saba on the Abyssinian coast, where they may be plentifully supplied: but it must be remembered, "that the people here are Gaila, the most treacherous and villanous wretches on earth." Here not only wa ter may be procured, but plenty of sheep, goats, with some myrrh, and incense in the proper season.-Great caution, however, must be used in dealing with the people, as even those of Mocha, who are absolutely neces sary to them in their commercial dealings, cannot trust them without surety or hostages. Not many years ago, the surgeon and mate of the Elgin East Indiaman, with several other sailors, were murdered by these savages as they went ashore to purchase myrrh, though they had a letter of safe conduct from the shekh.

To such as do not want to be known, our author recommends a low black island on the coast of Arabia, named Camaran, in latitude 15° 30'. It is distinguished by a white house or fortress on the west end of it; where water is to be had in still greater plenty than at Azab; but no provisions, or such only as are very bad, can be procured. If it is necessary not to be seen at all on the coast, the island of Foosht is recommended by our author as having excellent water, with a saint or monk, whose office is to keep the wells clean. This is one of the chain of islands which stretches almost 4 P 2

across

resolved, I shall take it for granted that no such differ- Rrd Ses ence of level exists, whatever Ptolemy's engineers might have pretended to him; because, to suppose it fact, is Reddle. to suppose the violation of one very material law of na

ture."

Red Sea. across the gulf from Loheiah to Masuab, and from actual observation by Mr Bruce, is found to be situated in N. Lat. 15° 59' 43". E. Long. 42° 47'. From this to Yamboo there is a safe watering-place; and there is an absolute necessity for having a pilot before you come to Ras Mahomet; because over the Elanitic gulf, the mountains of Aucha, and the cape itself, there is often a thick haze, which lasts for many days together, and a number of ships are lost by mistaking the eastern bay or Elanitic gulf for the entrance of the gulf of Suez; the former has a ridge of rocks nearly across it. After reaching Sheduan, a large island, about three leagues farther in a north-by-west direction, there is a bare rock distinguished by no particular name; but so situated that ships ought not to come within three leagues of it. This rock is to be left to the westward at the distance just mentioned; after passing which you meet with shoals forming a pretty broad channel, with soundings from 15 to 30 fathoms; and again, on standing directly for Tor, there are two other oval sands with sunk rocks in the chan

nel, between which you are to steer. Tor may be known at a distance by two hills that stand near the water-side; which, in clear weather, may be seen six leagues off. Just to the south-east of these is the town and harbour, where there are some palm trees about the houses, the more remarkable, as being the first that are seen on the coast. The soundings in the way to Tor harbour are clean and regular; "and, by giving the beacon a small birth on the larboard hand, you may haul in a little to the northward, and anchor in five or six fathom." In spring tides, it is high water at Tor nearly about 12 o'clock in the middle of the gulf there is no perceptible tide, but at the sides it runs at the rate of more than two knots in the hour. Tor itself is but a small village, with a convent of monks belonging to those of Mount Sinai. It was taken by Don John de Castro, and fortified, soon after its discovery by the Portuguese; but has never since been a place of any consideration; serving now only for a watering place to the ships trading to or from Suez.— From this place there is a distinct view of Mounts Horeb and Sinai, which appear above and behind the others, with their tops frequently covered with snow in the winter.

Mr Bruce next proceeds to consider some questions which may be reckoned matters of curiosity rather than any thing else. One of these is concerning the level of the water of this sea itself, which has been supposed several feet above that of the Mediterranean. "To this (says our author) I answer, that the fact has been supposed to be so by antiquity, and alleged as a reason why Ptolemy's canal was made from the bottom of the Heroopolitic gulf rather than brought due north across the isthmus of Suez; in which last case it was feared it would submerge a great part of Asia Minor. But who has ever attempted to verify this by experiment? or who is capable of settling the difference of levels, amounting, as supposed, to some feet and inches, between two points 120 miles distant from each other, over a desert that has no settled surface, but is changing its height every day? Besides, since all seas are in fact but one, what is it that hinders the Indian ocean to flow to its level? What is it that keeps the Indian ocean up? Till this last branch of the question is

2

The next thing considered by our author is the passage of the Israelites through the Red Sea. At the place where he supposes the passage to have been, the sea is not quite four leagues broad, so that it might easily have been crossed in one night without any miracle. There is about 14 fathom water in the channel, and nine at the sides, with good anchorage every where; the farthest side is a low sandy coast, and a very easy landing place. "The draught of the bottom of the gulf (says he) given by Dr Pococke, is very erroneous in every part of it. It was proposed to Mr Niebuhr, when in Egypt, to inquire upon the spot, whether there were not some ridges of rocks where the water was shallow, so that an army at particular times might pass over? Secondly, whether the Etesian winds, which blow strongly all summer from the north-west, could not blow so violently against the sea, as to keep it back on a beap, so that the Israelites might have passed without a miracle? And a copy of these queries was left for me to join my inquiries likewise. But I must confess, however learned the gentlemen were who proposed these doubts, I did not think they merited any attention to solve them. If the Etesian winds, blowing from the north-west in summer, could keep up the sea as a wall on the right or to the south, of fifty feet high, still the difficulty would remain of building the wall on the left hand or to the north. Besides, water standing in that position for a day, must have lost the nature of a fluid. Whence came that cohesion of particles that hindered that wall to escape at the sides? This is as great a miracle as that of Moses. If the Etesian winds had done this once, they must have repeated it many a time before and since, from the same causes. Yet Diodorus Siculus says, the Troglodytes, the indigenous inhabitants of that very spot, had a tradition from father to son, from their very earliest and remotest ages, that once this division of the sea did happen there; and that, after leaving the bottom some time dry, the sea again came back and covered it with great fury. The words of this author are of the most remarkable kind. We cannot think this heathen is writing in favour of revelation. He knew not Moses, nor says a word about Pharaoh and his host; but records the miracle of the division of the sea in words nearly as strong as those of Moses, from the mouths of unbiassed undesigning pagans."

RED-Shank. See SCOLOPAX,

RED-Start. See MOTACILLA, ORNITHOLOGY Index. RED-Wing. See TURDUS,

REDANS, in Field Fortification. See the article REDENS.

REDDENDUM, in Law, is used substantively for the clause in a lease wherein the rent is reserved to the lessor. The proper place for it is next after the limita tion of estate.

REDDITIO, was the third part of the sacrifice of the heathens, and consisted of the solemn act of putting in again the entrails of the victims, after they had been religiously inspected. See SACRIFICE.

REDDLE, a soft, heavy, red, ferruginous earth, of

great

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REDEMPTION, in Law, a faculty or right of reentering upon lands, &c. that have been sold and assigned, upon reimbursing the purchase-money with legal costs.

REDEMPTION, in Theology, denotes the recovery of mankind from sin and death, by the obedience and sacrifice of Christ, who on this account is called the Redeemer of the world. See THEOLOGY.

REDENS, REDANS, or Redant, in Fortification, a kind of indented work in form of the teeth of a saw, with salient and re-entering angles; to the end that one part may flank or defend another. It is likewise called saw-work and indented work. The lines or faces in this flank one another.

Redens are used in fortifying walls, where it is not necessary to be at the expence of building bastions ; as when they stand on the side of a river running through a garrison town, a marsh, the sea, &c. But the fault of such fortification is, that the besiegers from one battery may ruin both the sides of the tenaille or front of a place, and make an assault without fear of being enfiladed, since the defences are mined. The parapet of the corridor is likewise often redented or carried on by the way of redens. The redens was used before bastions were invented, and some people think them preferable.

REDI, FRANCIS, an Italian physician and polite scholar, was born at Arezzo in Tuscany in 1626. His ingenuity and learning recommended him to the office of first physician to Ferdinand II. duke of Tuscany; and he contributed not a little toward the compiling of the Dictionary of La Crusca. He wrote upon vipers, upon the generation of insects, and composed a good deal of poetry. All his writings are in Italian; and his language is so fine and pure, that the authors of the Dictionary of La Crusca have often cited it as a standard of perfection. He died in 1697.

REDINTEGRATION, is the finding the integral or fluent again from the fluxion. See FLUXIONS.

REDOUBT, in Fortification, a small square fort, without any defence but in front; used in trenches, lines of circumvallation, contravallation, and approach; as also for the lodgings of corps-de-gard, and to defend passages.

REDUCTION, in the schools, a manner of bring ing a term or propositions, which was before opposite to some other, to be equivalent to it.

REDUCTION, in Arithmetic, that rule whereby numbers of different denominations are brought into one denomination. See ARITHMETIC.

REDUCTION of Equations, in Algebra, is the clearing them from all superfluous quantities, bringing them to their lowest terms, and separating the known from the unknown, till at length only the unknown quantity is found on one side, and known ones on the other. The reduction of an equation is the last part of the resolution of the problem. See ALGEBRA.

REDUCTION of a figure, design, or draught, is the making a copy thereof, either larger or smaller than the original; still preserving the form and proportion. The great use of the proportional compasses is the reduction

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of figures, &c. whence they are called compasses of re- Reduction duction. See the article COMPASS.

There are various methods of reducing figures, &c. Redundant. the most easy is by means of the pentagraph, or parallelogram; but this hath its defects. See the article PENTAGRAPH.

The best and most usual methods of reduction are as

Plate

fig. 1.

follow: 1. To reduce a figure, as ABCDE (fig. 1.), into a less compass. About the middle of the figure, ccccXLVIII. as z, pitch on a point, and from this point draw lines to its several angles A, B, C, &c. then drawing the line ab parallel to AB, be parallel to BC, &c. you will have the figure abcde similar to ABCDE.

If the figure a bede had been required to be enlarged, there needed nothing but to produce the lines from the point beyond the angles, as ≈ 1), ≈ C, &c. and to draw lines, viz. DC, CB, &c. parallel to the sides dc, cb, &c.

2. To reduce a figure by the angle of proportion, suppose the figure ABCDE (fig. 2.) required to be di-Fig. 2. minished in the proportion of the line AB to ab (fig. 3.) draw the indefinite line GH (fig. 4.), and from Fig, 3. G to H set off the line AB. On G describe the arch and 4. HI. Set off the line ab as a chord on HI, and draw GI. Then with the angle IGH you have all the measures of the figure to be drawn. Thus to lay down the point c, take the interval BC, and upon the point G describe the arch KL. Also on the point G describe MN; and upon A, with the distance MN, describe an arch cutting the preceding one in c, which will determine the side bc. And after the same manner are the other sides and angles to be described. The same process will also serve to enlarge the figure.

3. To reduce a figure by a scale. Measure all the sides of the figure, as ABCDE (fig. 2). by a scale, and lay down the same measures respectively from a smaller scale in the proportion required.

4. To reduce a map, design, or figure, by squares. Divide the original into little squares, and divide a fresh paper of the dimensions required into the same number of squares, which are to be larger or less than the former, as the map is to be enlarged or diminished. This done in every square of the second figure, draw what you find in its correspondent one in the first.

REDUCTION, in Metallurgy, is the bringing back metalline substances which have been changed into scoriæ or ashes, or otherwise divested of their metallic form, into their natural and original state of metals again. See ORES, Reduction of.

REDUCTION, in Surgery, denotes an operation whereby a dislocated, luxated, or fractured bone, is restored to its former state or place.

REDUNDANCY, a fault in discourse, consisting in the use of a superfluity of words. Words perfectly synonymous are redundant, and ought to be retrenched.

REDUNDANT, in Music. What the French call une accord superflue, which we have translated a redundant chord in the article MUSIC (from D'Alembert), has by others been rendered a chord extremely sharp, as in the translation of Rameau's Principles of Composition. Their nature will be best understood by a few examples, and an account of the number of tones, semitones, or lesser intervals, contained in each.

The second redundant is composed of a major tone,

and

RE-EXCHANGE, in commerce, a second payment Re Exof the price of exchange, or rather the price of a new chane

Redundant and a minor semitone; as from fa to sol sharp. Its proportion is as 64 to 75. Reeving.

The third redundant consists of two tones and a semitone, as fa la, sharp. Its proportion is as 96 to 125. The fourth redundant is the same with the tritone. From these examples compared with the same intervals in their natural state, the reader may form a general idea of what is meant by redundant.

REE, REIS, or Res, a little Portuguese coin. See MONEY-Table.

REED, in Botany See ARUNDO and BAMBOO. There are two sorts of reeds, says Hasselquist, growing near the Nile. One of them has scarce any branches; but is furnished with numerous leaves, which are narrow, smooth, channeled on the upper surface; and the plant is about 11 feet high. The Egyptians make ropes of the leaves. They lay them in water like hemp, and then make them into good strong cables. These, with the bark of the date tree, form almost the only cable used in the Nile. The other sort is of great consequence. It is a small reed, about two or three feet high, full branched, with short, sharp, lancet-shaped leaves. The roots, which are thick as the stem, creep and mat themselves together to a considerable distance. This plant seems useless in common life; but to it, continues the learned author, is the very soil of Egypt owing: for the matted roots have stopped the earth which floated in the waters, and thus formed, out of the sea, a country that is habitable.

Fire REEDS. See FIRE-Ship.

REED, a term in the west of England for the straw used by thatchers, which is wheat straw finely combed, consisting of stiff, unbruised, and unbroken stalks of great length, carefully separated from the straw used for fodder by the thresher, and bound in sheaves or nitches, each of which weighs 281b. and are sold from 21s. to 31s. per hundred nitches, according to the season. This is a great improvement in the art of thatch ing, as it gives a finish to the work which cannot be attained by straw, rough and tumbled together, without any separation of the long and short: it is also a readier mode of working.

REEF, a term in navigation. When there is a great gale of wind, they commonly roll up part of the sail below, that by this means it may become the narrower, and not draw so much wind; which contracting or taking up the sail they call a reef, or reefing the sail: so also when a top-mast is sprung, as they call it, that is when it is cracked, or almost broken in the cap, they cut off the lower piece that was near broken off, and setting the other part, now much shorter, in the step again, they call it a reefed top-mast.

REEL, in the manufactories, a machine serving for the office of reeling. There are various kinds of reels; some very simple, others very complex.

REELING, in the manufactories, the winding of silk, cotton, or the like, into a skain, or upon a button, to prevent its entangling. It is also used for the charging or discharging of bobbins, or quills, to use them in the manufacture of different stuffs, as thread, silk, cotton, &c. Reeling is performed in different ways, and on different engines.

REEVING, in the sea-language, the putting a rope through a block: hence to pull a rope out of a block, is called unreeving.

exchange due upon a bill of exchange that comes to be Reflections protested, and to be refunded the bearer by the drawer or indorser.

REFECTION, among ecclesiastics, a spare meal or repast, just sufficient for the support of life: hence the hall in convents, and other communities, where the monks, nuns, &c. take their refections or meals in common, is called the refectory.

REFERENCE, in writing, &c. a mark relative to another similar one in the margin, or at the bottom of the page, where something omitted in the text is added, and which is to be inserted either in reading or copying.

REFINING, in general, the art of purifying a thing; including not only the essaying or refining of metals, but likewise the depuration or clarification of liquors. See CLARIFICATION; and PHARMACY, UDder MATERIA MEDICA; and ORES, Reduction of.

Gold and silver may be refined by several methods, which are all founded on the essential properties of these metals, and acquire different names according to their kinds. Thus, for instance, gold having the property which no other metal, nor even silver, has of resisting the action of sulphur, of antimony, of nitrous acid, or marine acid, may be purified by these agents from all other metallic substances, and consequently may be refined. These operations are distinguished by proper names, as purification of gold by antimony, parting, concentrated parting, dry parting. The term refining is chiefly applied to the purification of gold and silver by lead in the cupel. See ORES, Reduction of.

REFLECTION, the return or progressive motion of a moving body, occasioned by some obstacle which hindered it from pursuing its former direction.

Circular Instrument of REFLECTION, an instrument for measuring angles to a very great degree of accuracy. It was invented by the celebrated astronomer Mr Tobias Mayer of Gottingen, principally with a view to do away the errors of the divisions of the limb; and has since been much improved by the Chevalier de Borda, and M. J. H. de Magellan. This instrument is particularly applicable to the measuring of the distances of the heavenly bodies, and was used by the French in their part of the operation for determining the difference of meridians of Paris and Greenwich. For the description, rectification, and use of this instrument, see NaVIGATION.

REFLECTION of the Rays of Light, in Catoptrics, is their return, after approaching so near the surface of bodies as to be thereby repelled or driven backwards. For the causes of reflection, see OPTICS Index, at Rays of Light, and Reflection of Light, &c. For the application of the doctrine of reflection to mirrors, see OPTICS. See also MIRROR, BURNING Glass, and GlassGRINDING ; and for the coating or foliating of mirrors, see the article FOLIATING of Looking glasses, &c. See also TELESCOPE.

REFLECTION of Heat, see CHEMISTRY, N° 170. REFLECTION of Cold. For an account of this curious phenomenon, see also CHEMISTRY, No 272.

It has been generally supposed that this fact was first noticed by Professor Pictet of Geneva; but we have been informed from good authority (for we have not

yet

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