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a place of great antiquity. It was anciently confined to the S.side of the Liftey. In the 10th century, after the fortifications ofDublin were repaired by the Ostmen, the walls of the city, includ-ing those of the castle, did not occupy more than an Irish mile.Ptolemy , who nourished about A. D. 140, says, it was ancientlycalled Aschcled. In 155, Alpinus, whose daughter Aulianawasdrowned in the Liffey , changed the name from Aschcled to Ail-liana. It was afterwards named Dublana, and Ptolemy calls itEblana. Dublana, (whence Dublinnm and Dublin, ) is evidentlyderived from Dtib leana, the place of the black harbour or lake,or rather the lake of the sea; the bay of Dublin being frequentlyso called. The city has had a variety of names. The Irish call itDrom-choll-coil, “ the brow of a liazle wood.” In 181, Eoganking of Munster being on a royal tour, paid a visit to this place,which was then called Atha Cliath-Dubb-Line, “ the passage ofthe ford of hurdles over the black pool.” This city has two ca-thedrals, 18 parish-churches, two chapels,, of ease, 15 Roman ca-tholic chapels, six meeting houses for presbyterians. one for ana-babtists, four for methodists, two for quakers, a church for French Calvinists, a Danish and a Dutch church, and a Jewish synagogue.
Dublin, a town of Pennsylvania, in Philadelphia county ; 10miles N. E. of Philadelphia .
DUBOS, John Bai-tist, a learned and ingenious French au-thor, born at Beauvais in 1670. lie fini-hed his studies at Paris ,and was intrusted with the management of several important affairsin Italy, England and Holland. At his return to Paris , he got |prebendary: atterwards he had a pension of 2000 livres, and tin-abbey of Notre Dame at Ressons, near Beauvais. He died atParis, when perpetual secretary of the French academy, on the23d March, 1742. His principal works are, 1. Critical Reflec-tions on Poetrv and Painting , 3 vols. 12ino. 2 A Critical Historyof the French Monarchy in Gaul, 2 vols. 4to.
DUCALS, letters patent granted by the senate of Venice, orwrote in the name of the senate, to foreign princes: so named be-cause the name of the doge or duke was prefixed to them.
DUCAS, a learned Greek, who wrote a history of what passedunder the last emperors of Constantinople , till the ruin of that city.This work, which is esteemed, was printed at the Louvre in 1649,with the Latin translation, and notes of Bouillaud.
DUCAT , a coin chiefly of gold. The origin of ducats is as-signed by Procopius, to Longinus, governor of Italy ; who, re-volting against the emperor Justin II., made himself duke of Ra-venna , and called himself Exarcha, i. c. without lord or ruler;and, to shew his independence, struck pieces of money, of very-pure gold, in his own name, and with his own stamp, which werecalled ducati. Du Cange affirms, that the first ducats were struckin the cluchv of Apulia . The chief gold ducats are, the single anddouble ones of Venice, Florence, Genoa, Germany, Hungary ,Poland, Sweden, Denmark, Flanders Holland, and Zurich . Thedouble ducats weigh from five pennyweights 17 grains, to fivepennyweights lOgrains; and the single in proportion. The Spa-niards have no ducats of gold ; and the silver one, with them, is noreal species, hut only a money of account like our pound. It isequivalent to 11 rials. The silver ducats of Florence serve therefor crow ns.
DUCATOON, a silver coin, struck chiefly in Italy , thoughthere are al o Dutch and Flemish ducatoons. They are valuedat about 4s. 8d. or 4s. lOd. according to the rate of bullion.There is also a gold ducatoon, current principally in Holland : itis equivalent to 20 florins, at the rate of Is. I l^d. the florin.
DUCENARIUS, in antiquity, an officer of the
Roman army, who had the command of 200 men.
DUCENiESIMA, in antiquity, a tax of the 200dth penny,exacted by the Romans.
DUCES TECUM , inlaw, a writ that commands a person toappear in the court of chancery, and bring with them certain wri-tings, evidences, or other things, which the court is inclined toview.
DUCK, in ornithology. Sec Anas and Decoy. This fowlis furnished with a peculiar structure of vessels about the heart,which enables it to live a considerable time under water, as isnecessary for it in diving.
DUCKING, a sort of marine punishment, inflicted by theFrench before the revolutions on tho.e who had been convictedof desertion, blasphemy, or sedition. It was thus performed : The
criminal was placed astride of a short thick batten, fastened to theend of a rope, which passed through a block hanging at one of theyard-arms. Thus fixed, he was hoisted suddenly up to the yard,and the rope being slackened at once, he was plunged into the sea.This wgs repeated several times conformably to the sentencerga'iist .the culprit, who had uisosevetal cannon-shot fastened to hishlt-t,... A gun was also fired to advertise the other ships of the fleet,tliat their crews might become spectators.
Ducking is also a penalty which veteran sailors pretend to havea right to inflict on those who, for the first time, pass the tropic ofCancer, the equator, or the straits of Gibraltar, in consequence oftheir refusal or incapacity to pay the usual line levied on such oc-casions.
DUCKSFOOT. See Podophyllum.
DUCK UP, is a phrase used at sea by the steer’s man, when themain-sail, fore-sail, or sprit-sail, hinder his seeing to steer by aland-mark: upon which tie calls out, duck up the dew-lines"ofthese sails, that is, hale the sails out of the way. V hen a shot ismade by a chace-piece, i! the clew of the sprit-sail hinder the sight,they call out, duck up, &c.
DUCT, DUCTUS, ill general, denotes any tube or canal. Itis much used by anatomists, who mention the adipose ducts, thethoracic, or chyhferous duct ; the excretory ducts oi the glands;the hepatic duct; the salival ducts; the lachrymal ducts; the duc-tus communis choledochus, &c. Their use is to convey thefluids of the body to the parts to which they belong. See Ana-tomy.
DUCTILITY, in phy sics, a properly possessed by certain solidbodies, which consists in their yielding to percussion or pressure,and in receiving dilierent forms without breaking. Some bodiesare ductile in all circumstances. Such are metals, particularlygold and silver. Other bodies are duetde only when heated to asufficient degree; such as wax and other substances of that kind,and glass. Other bodies, particularly some kinds of iron, calledby the workmen red-shor , brass,and some other metallic mixtures,are ductile only when cold, and br tile when hot. 'I he degreesof heat requ site to produce ductil.lv in bodies of the tir-t kind,vary according to their dilierent natures. The great duitlhvofsome bodies, especially gold, is very surprising: the guld-lx atersand wire-drawers furnish us with abundant proofs of this proper! \ ;they every day reduce gold, into lamella- inconceivably thin, y etwithout the least aperture or pore discoverable, even by the mi-croscope: a single grain of gold may be stretched under the ham-mer, into a leal that will cov< r a house, and yet the leaf remain socompact as not to transmit the rays of light, nor even admit spiritof wine to transude. Dr. Halley took the follow ing met hod tocompute the ductility of gold : he learned from the wire-drawers,that an ounce of gold is sufficient to gild, that is, to cover or coat,a silver cy linder ot forty-eight ounces weight, which cylinder mayhe drawn" out into a wire so very line, that two yards shall weighonly one grain; and consequently ninety-eight yards of the samewire, only forty-nine grains: so that a single grain of gold heregilds ninety-eight yards; and ot course, the leii-lhoiis,:ndth part ofa grain is here above one-third ot an inch long. And since thethird part of an inch is yet capable ot being divided into ten lessparts visible to the naked eye, it is evident (hat the hundred thou-sandth part of a grain of gold may he seen without the assistance ofa microscope. 1’roceeding in his calculation, he found, at length,that a cube of gold, whose side is the hundredth part of an inch,contains 2,433,000,000 visible parts; and yet, though the goldwith which such wire is coated, is stretched to such a degree, sointimately do its parts cohere, that there is not any appearance ofthe colour of the silver underneath. Mr. Boyle, examining someleaf-gold, found that a grain and a quarter m weight took up artarea of fifty square inches; supposing therefore the leaf divided byparallel lilies 100th part of an inch apart, a grain of gold will bedivided into five hundred thousand minute squares, all discernibleby a good eye: for the same author shew-s, than an ounce ot golddrawn out in wire would reach 155 miles and a half. But Mr.Reaumur has carried the ductility of gold to a still greatrr extent.VVliat is railed gold-wire, every body knows, is only a silver onegilt. 'I’he cvlinder of silver, covered with leaf-gold, they drawthrough the iiole of an iron, and the gilding still keeps pace withthe wire, stretch it to what length they can. Now- Mr. Reaumurshews, that in the common way of drawing gold-wire, a cylinder of4 silver