35°, the azimuth distance sought.

91. When the altitude is given, find from thence the hour, and proceed as above. This praxis is of singular use on many occasions; as, 1. In finding the declination of vertical planes more exactly than in the common way, especially if the transits of the sun's centre are observed by applying a ruler with sights, either plain or telescopical, to the wall or plane whose declination is required. 2. In drawing a meridian line, and finding the magnetic variation. 3. In finding the bearings of places in terrestrial surveys; the transits of the sun over any place, or his horizontal distance from it, being observed; together with the altitude and hour; and thence determining small differences of longitude. 4. In observing the variations at sea, &c.

OF FINDING THE DECLINATION, INCLINATION, AND RECLINATION OF PLANES.

92. The declination, inclination, and reclination of planes are frequently taken with a sufficient degree of accuracy by an instrument called the declinator or declinatory.

92.* The construction of this instrument, as somewhat improved by Mr. Jones, is thus: On a mahogany board is inserted a semicircular arch of ivory or box-wood, divided into two quadrants of 90° each, beginning from the middle. On the centre of this arch turns a vertical quadrant, which is divided into 90°, beginning from the base; on which is a moveable index, with a small hole for the sun's rays to pass through, and form a bright spot on a certain mark. The lower extremity is pointed, to mark the linear direction of the quadrant when applied to any other plane; as this quadrant takes off occasionally, and a plumb-line hangs at the centre, for taking the inclinations and reclinations of planes. On the plane of the board is inserted a compass of points and degrees, with a magnetical needle turning on a pivot over it. See DECLI

NATORY.

93. The addition of the moveable quadrant and index considerably extend the utility of the declinator, by rendering it convenient for taking equal altitudes of the sun, the sun's altitude, and bearing, at the same time, &c. To apply this instrument in taking the declination of a wall or plane: Place the back part of it in a horizontal direction to the plane proposed, and observe what degree or point of the compass the N. part of the needle stands over from the north or the south, and it will be the declination of the plane from the north or south accordingly. In this case, allowance must be made for the variation of the needle (if any) at the place; and which,

if not previously known, will render this operation very inaccurate.

94. But the most exact way for taking the declination of a plane, or finding a meridian line, by this instrument, is, in the forenoon, about two or three hours before twelve o'clock, to observe two or three heights or altitudes of the sun; and at the same time the respective angular polar distances. Write these down; and in the afternoon watch for the same, or one of the same altitudes, and mark the angular distances or dis tance on the quadrant; the division or degree exactly between the two noted angular distances will be the true meridian, and the distance at which it may fall from the centre of the divisions, will be the declination of the plane. The reason for observing two or three altitudes and angles in the morning is, that in case there should be clouds in the afternoon, we may have the chance of one corresponding altitude.

OF THE RIGHT PLACING OF DIALS. 95. The plane on which the dial is to rest being duly prepared, and every thing necessary for fixing it, you may find the hour with tolerable exactness by a large equinoctial ring-dial, and set your watch to it. And then the dial may be fixed by the watch at your leisure.

96. If you would be more exact, take the sun's altitude by a good quadrant, noting the precise time of observation by a clock or watch. Then compute the time for the altitude observed; and set the watch to agree with that time, according to the sun. Hadley's quadrant is very convenient for this purpose: for by it you may take the angle between the sun and his image reflected from a basin of water; the half of which angle, subtracting the refraction, is the altitude required.

97. This is best done in summer; and the nearer the sun is to the prime vertical, the east or west azimuth, when the observation is made, so much the better. Or, take two equal altitudes of the sun in the same day; one any time between seven and ten in the morning, the other between two and five in the afternoon; noting the moments of these two observations by a clock or watch: and if the watch shows the observations to be at equal distances from noon, it agrees exactly with the sun: if not, the watch must be corrected by half the difference of the forenoon and afternoon intervals; and then the dial may be set true by the watch.

98. For example, suppose you had taken the sun's altitude when it was twenty minutes past VIII in the morning by the watch; and found, by observing in the afternoon, that the sun had the same altitude ten minutes before IV; then it is plain, that the watch was five minutes too fast for the sun: for five minutes after XII is the middle time between VIII h. 20 m. in the morning, and III h. 50 m. in the afternoon; and, therefore, to make the watch agree with the sun, it must be set back five minutes.

99. In many cases, where the situation is suitable, it is very desirable to have a true meridian line for the regulation of clocks and watches; we shall, therefore, here insert Mr. Ferguson's method of constructing one.

Make a round hole, about a quarter of an inch diameter, in a thin plate of metal; and fix the plate in the top of a south window, in such a manner that it may recline from the zenith at an angle equal to the colatitude of your place, as nearly as you can guess: for then the plate will face the sun directly at noon on the equinoctial days. Let the sun shine freely through the hole into the room; and hang a plumb-line to the ceiling of the rooin, at least five or six feet from the window, in such a place as that the sun's rays, transmitted through the hole, may fall upon the line when it is noon by the clock; and having marked the said place on the ceiling, take away the line.

Having adjusted a sliding bar to a dovetail groove, in a piece of wood about eighteen inches long, and fixed a hook into the middle of the bar, nail the wood to the above-mentioned place on the ceiling parallel to the side of the room in which the window is; the groove and the bar being towards the floor: then hang the plumbline upon the hook in the bar, the weight or plummet reaching almost to the floor; and the whole will be prepared for further and proper adjustment.

This done, find the true solar time by either of the last two methods, and thereby regulate your clock. Then, at the moment of the next noon by the clock, when the sun shines, move the sliding bar in the groove, until the shadow of the plumbline bisects the image of the sun, made by his rays transmitted through the hole, on the floor, wall, or on a white screen placed on the north side of the line; the plummet at the end of the line hanging freely in a pail of water placed below it on the floor.-But because this may not be quite correct for the first time, on account that the plummet will not settle immediately, even in water; it may be farther corrected on the following days, by the above method, with the sun and clock; and so brought to a very great exactness. The rays transmitted through the hole will cast but a faint image of the sun, even on a white screen, unless the room be so darkened that no sunshine may be allowed to enter but what comes

through the small hole in the plate. And always, for some time before the observation is made, the plummet ought to be immersed in a jar of water, where it may hang freely; by which means the line will soon become steady, which otherwise would be apt to continue swinging.

OF THE DOUBLE HORIZONTAL, THE BABYLONIAN AND ITALIAN DIALS.

100. Sometimes a stereographic projection of the hour circles, and the parallels of the sun's declination, is added to the gnomonic projection, on the same horizontal plane; the upright side of the gnomon being sloped into an edge, standing perpendicularly over the centre of the projection: so that the dial, being in its due position, the shadow of that perpendicular edge is a vertical circle passing through the sun, in the stereographic projection. The months being duly marked on this dial, the sun's declination, and the length of the day at any time, are had by inspection; as also his altitude, by means of a scale of tangents. But its chief property is, that it may be placed true, whenever the sun shines, without the help of any other instrument.

101. The Babylonian and Italian dials reckon the hours, not from the meridian as with us, but from the sun's rising and setting. Thus, in Italy, an hour before sun-set is reckoned the twentythird hour; two hours before sun-set the twentysecond hour; and so of the rest. And the shadow that marks them on the hour-lines, is that of the point of a stile. This occasions a perpetual variation between their dials and clocks, which they must correct from time to time, before it arises to any sensible quantity, by setting their clocks so much faster or slower. And in Italy, they begin their day, and regulate their clocks, not from sunset, but from about mid-twilight, when the Ave Maria is said; which corrects the difference that would otherwise exist between the clock and the dial. The improvements which have been made in all sorts of instruments and machines for measuring time, have rendered these dials of little

account.

DIALLING in a mine, called also plumbing, is the using of a compass, which the miners call dial, and a long line to know which way the load or vein of ore inclines, or where to shift an airshaft, or bring an adit to a desired place.

DIALLING LINES, or DIALLING SCALES. See DIALLING, Index.

DIALLING SECTOR is a sector having upon it, besides other lines, the dialling lines, the construction of which is shown under DIALLING. It is evident that some advantage will be obtained in the practice of dialling by having the line placed on a sector. See SECTOR.

DIALLING SPHERE, is an instrument made of brass, with several semicircles sliding over one another, on a moving horizon, to demonstrate the nature of the doctrine of spherical triangles, and to give a true idea of the drawing of dials on all manner of planes.

DIALLING TRIGON, an instrument invented by Mr. Benjamin Martin, consisting of two graduated scales and a plane, used by some in the practice of dialling.

DIALECT, n. s. Fr. dialecte; Span. dialecto; Ital. dialetto; Lat. dialectus; Gr. diadeKToo, from dia and Xeyw, to speak. Language; style; the mode of expression peculiar to a certain district.

When themselves do practise that whereof they

write, they change their dialect; and those words they shun, as if there were in them some secret sting.

DIALECT is an appellation given to the lan guage of a province, in so far as it differs from that of the whole kingdom. The term is particularly used in speaking of the ancient Greek, whereof there were four dialects, each of which was a perfect language in its kind, that took place in certain countries. In Great Britain, besides the two dialects of English and Scotch, almost every county has a dialect of its own, all differing considerably in pronunciation, accent, and tone, although one and the same language.

DIALECTICS, in the literary history of the ancients, that branch of logic which taught the rules and modes of reasoning. See LOGIC. Zeno Eleates was the first who discovered the natural series of principles and conclusions observed in reasoning, and formed an art thereof in form of a dialogue; which, for this reason, was called dialectica. The dialectica of the ancients is usually divided into several kinds: The first was the eleatica, that of Zeno Eleates, which was and contentionum. The first consisting of rules threefold; viz. consecutionum, colloqutionum, for deducing or drawing conclusions. The second, the art of dialogue; which became of such universal use in philosophy, that all reasoning was called interrogation: then, syllogism being laid aside, the philosophers used dialogue, and required the respondent to conclude and argue from the several concessions made. The last part of Zeno's dialectics, pigien, was contentious, or the art of disputing and contradicting; though some, particularly Laertius, ascribe this part to Protagoras a disciple of Zeno.

The second is the dialectica megarica, whose author is Euclid, as of Megara. He gave much

into the method of Zeno and Protagoras; though there are two things appropriated to him: the first, that he impugned the demonstrations of others, not by assumptions, but conclusions; continually making illations, and proceeding from consequence to consequence: the second, that he set aside all arguments drawn from comparisons of similitude as invalid. He was succeeded by Eubulides, from whom the sophistic way of reasoning is said to be derived. In his time the art is described as manifold: mentiens, fallens, electra, obvelata, arcevalis, cornuta, and calva. See SOPHISM.

The third is the dialectica of Plato, which he proposes as a kind of analysis to direct the human mind, by dividing, defining, and bringing things to the first truth; where being arrived, it applies itself to explain sensible things, but with a view to return to the first truth where alone it can rest. Such is the idea of Plato's analysis.

The fourth is Aristotle's dialectica: containing the doctrine of simple words, delivered in his book of Prædicaments; the doctrine of propositions, in his book De Interpretatione; and that of the several kinds of syllogism, in his books of Analytics, Topics, and Elenchuses.

The fifth is the dialectica of the Stoics; which they call a part of philosophy, dividing it into rhetoric and dialectic; to which some add the definitive, whereby things are justly defined; comprehending likewise the canons or criterions of truth. The Stoics, before they treat of syllogisms, have two principal places; the one about the signification of words, the other about the things signified. On occasion of the first, they consider abundance of things belonging to the grammarian's province: what, and how many letters; what is a word, diction, speech, &c. On occasion of the latter, they consider things themselves, not as without the mind, but as in it, received in it by means of the senses. Accordingly, they first teach, that nil sit in intellectu, quod non prius fuerit in sensu; 'whatever is in the mind came thither by the senses;' and that aut incursione sui, as Plato, who meets the sight; aut similitudine, as Cæsar by his effigy; aut proportione, either by enlarging as a giant, or by diminishing as a pygmy; aut translatione, as a Cyclops; aut compositione, as a Centaur; aut contrario, as death; aut privatione, as a blind man.

The sixth is Epicurus's dialectica: who had recourse to certain canons, the collection whereof he called Canonica; and as all questions in philosophy are either de re or de voce, he gave separate rules for each.

DIALECTICK, n. s. Diaλektin. Logic; the art of reasoning. See DIALECT.

DIALECTICAL, adj. Logical; argumen

tative.

Those dialectical subtleties, that the schoolmen employ about physiological mysteries, more declare the wit of him that uses them, than increase the knowledge of sober lovers of truth. Boyle.

DIALITHA, in the writings of the ancients, a word used to express the elegant ornaments of the Greeks and Romans, composed of gold and gems. They also called these lithocolla, cemented stones or gems; the gold being in this

In easy dialogues is Fletcher's praise; He moved the mind, but had not power to raise. Dryden. With the stars

And the quick Spirit of the Universe He held his dialogues; and they did teach To him the magic of their mysteries. Byron. DIALYSIS, in grammar, a mark or character, consisting of two points () placed over two vowels, because otherwise they would make a diphthong, as Mosaic, Phaeton, &c.

DIAMASTIGOSIS, a festival of Sparta, in honor of Diana Orthia, which received that name aо rov pasiyovv, from whipping, because boys were whipped before the altar of the goddess. These boys, called Bomonicæ, were originally free-born Spartans, but in the more delicate ages they were of mean birth, and generally of a slavish origin. This operation was performed by an officer in a severe and unfeeling manner; and that no compassion should be raised, the priest stood near the altar with a small light statue of the goddess, which suddenly became heavy and insupportable if the lash of the whip was less rigorous. The parents of the children attended the solemnity, and exhorted them not to show themselves, either by fear or groans, unworthy of Laconian education. These flagellations were so severe, that the blood gushed in profuse torrents, and many expired under the lash of the whip, without uttering a groan, or betraying any marks of fear. Such a death was reckoned very honorable, and the corpse was buried with much solemnity with a garland of flowers on its head. The origin of this festival is unknown. Some suppose that Lycurgus first instituted it to inure the youth of Lacedemon to bear labor and fatigue, and render them insensible to pain and wounds. Others maintain, that it is a mitigation of an oracle, which ordered that human blood should be shed on Diana's altar; and according to their opinion, Orestes first introduced that barbarous custom, after he had brought the statue of Diana Taurica into Greece. There is another tradition which mentions that Pausanias, as he was offering prayers and sacrifices to the gods, before he engaged with Mardonius, was suddenly attacked by a number of Lydians who disturbed the sacrifice, and were at last repelled with staves and stones, the only weapons with which the Lacedemonians were provided at that

moment. In commemoration of this, therefore, the whipping of boys was instituted at Sparta, and after that the Lydian procession.

Gr. διά and μετα pov, a measure. The

Certainly the price and virtue of things consist not in the quantity: one diamond is more worth than

The diamond is by mighty monarchs worn, Fair as the star that ushers in the morn.

Blackmore.

mous.

The space between the earth and the moon, according to Ptolemy, seventeen times the diameter of the earth, which makes, in a gross account, about one hundred and twenty thousand miles. Raleigh.

He made an instrument to know If the Moon shine full or no.

Tell what her diameter to an inch is, And prove that she's not made of green cheese. Hudibras.

He persuaded the king to consent to what was diametrically against his conscience and his honour, and, in truth, his security.

Clarendon.

Christian piety is, beyond all other things, diametrally opposed to profaneness and impiety of actions. Hammond.

Thus intercepted in its passage, the vapour, which cannot penetrate the stratum diametrically, glides along the lower surface of it, permeating the horizon

tal interval, which is betwixt the said dense stratum and that which lies underneath it. Woodward.

That the longer diameter of an ellipsis may be shortened, till it shall differ little from a circle, is indisputably true. Johnson.

DIAMETER. The line, which passing through the centre of a circle, or other curvilinear figure, divides it into equal parts. The impossibility of expressing the exact proportion of the diameter of a circle to a circumference, by any received way of notation, and the absolute necessity of bringing it as near the truth as possible, has induced some of the most celebrated men in all ages to endeavour to approximate it. The first who attempted it with success was the celebrated Van Cuelen, a Dutchman, who, by the ancient very laborious method, carried it to thirtysix decimal places; these he ordered to be engraven on his tomb-stone, thinking he had set bounds to improvement. However, the indefatigable Abraham Sharp carried it to seventy-five places in decimals; and since that time it has been carried much further.

}

DIAMOND, n. s. Į Fr. and Dut. diamant; DIAMONDED, adj. Ital. Span. and Port. diamante; Teut. demant, from Lat. adamas, adamantis ; Gr. αδαμας, αδαμαντος, i. e. α privative, and daμaw to subdue, because too hard to break or mould into shape. See the article below. A precious stone. Diamonded is, shaped like a diamond.

I see how thine eye would emulate the diamond : thou hast the right arch bent of the brow. Shakspeare.

The lively diamond drinks thy purest rays, Collected light, compact.

Thomson.

Shakspeare opens a mine which contains gold and diamonds in inexhaustible plenty, though clouded by with a mass of meaner minerals. incrustations, debased by impurities, and mingled Johnson.

The DIAMOND is a genus of siliceous earths, called adamas gemma by the Latins, demant by the Germans and Swedes, and diamant by the French, and is the hardest of all stones hitherto discovered. See ADAMAS. It was thought by the ancients that the diamond became soft and malleable, by steeping it in hot goat'sblood. Diamonds are found only in the East Indies, and in Brasil in South America. The diamond mines are in GOLCONDA, VISA POUr, BENGAL, and the island of BORNEO. See these articles. In the mines of Golconda are found a great number of stones from ten to forty carats, and upwards; and it was here that the famous diamond of Aurengzebe, the great mogul, was found, which before it was cut weighed 793 carats. The stones of this mine are not very clear; their water is usually tinged with the quality of the soil: being black where that is marshy; red where it partakes of red; and sometimes green and yellow, where the ground is of these colors. Another defect is a kind of greasiness appearing on the diamond, when cut, which takes off part of its lustre. There are usually not fewer than 60,000 persons, men, women, and children, at work in this mine. When the miners have found a place where they intend to dig, they level another somewhat bigger near it, and enclose it with walls about two feet high, leaving apertures from space to space, to give passage to the water. They dig twelve or fourteen feet deep, and till they find water. Then they cease, and the water thus found serves to wash the earth two or three times, after which it is let out at an aperture reserved for that purpose. This earth being well washed and dried, they sift it in a kind of open sieve, as we do corn; then thresh it, and sift it afresh; and lastly, search it well with the hands to find the diamonds. The miners work naked, except that they have a thin linen cloth before them. They have also inspectors, to prevent their concealing diamonds; which, however, they frequently do, by swallowing them when not observed.

Diamonds are commonly clear and pellucid, yet some are met with of a rose color, or inclining to green, blue, or black, and some have black specks. Tavernier saw one in the treasury of the mogul, with black specks in it, weighing about fifty-six carats; and he informs us, that yellow and black diamonds are produced in the mines at Carnatica. Mr. Dutens also relates, that he saw a black diamond at Vienna in the collection of the prince de Lichtenstein. Some