Thefe glaffes being properly painted, you place in the horizontal grooves the first, fecond, third, and fourth. Then draw up the curtain, by letting down the glafs on which it is painted, and draw away gently the fourth glafs, and after that the fecond; then advance very gently the fifth, that reprefents the embarkment, and pafs it quite through. Next pafs, the oppofite way, the fixth, which reprefents the Grecian fleet. The objects painted on the fourth, fifth, and fixth, quite difappearing, you are to advance the feventh, on which is painted the wooden horfe; and at the fame time the eighth, where the Trojans will appear to draw the horfe into the city. The curtain is then to be let down, that you may withdraw the scenes of the first act, and place in the grooves thofe that are to compofe the fecond.-In the fecond act may be reprefented the interior part of the city of Troy: on one fide may be feen the wooden horfe, and in the back part the temple of Pallas. The glaffes for this act may be painted in the following manner. On the first inay be palaces and houfes, reprefenting the infide of a city. On the fecond, the temple of Pallas in the centre, with a clear night and the moon. In the front may be feen the wooden horfe, that the Trojans have placed near the temple of Pallas. On the third, a troop of Greeks, with Sinon at their head, who are going to open the gates of the city to the Grecians. On the fourth, different troops of armed Greeks; painted on a long glafs, to afford variety. On the fifth, feveral troops of Trojans. On the fixth, various appearances of fire and smoke, fo difpofed, that, this glafs being drawn up above the others, the objects painted on the firft glafs may appear in a conflagration. Before you draw up the curtain, you should place the first and fecond glaffes. You then pass the whole third glafs flowly; a little after, the fourth, on which are painted the different bodies of armed Greeks; and at the fame time, from the oppofite fide, the fixth glafs, that represents the Trojan troops; obferving to move them flowly both in advancing and retreating, to imitate a combat (G). Then draw up, by degrees, the fixth, on which are painted the fire, flame, and fmoke, fo that the palaces and houfes painted on the first glafs may appear to take fire gradually, and at laft prefent a general conflagration. After having reprefented these incidents with the greatest attention, you let fall the curtain to prepare for the third act. In this may be reprefented the infide of Priam's palace; where is feen an altar, round which feveral Trojan princeffes appear, who have fled thither for fafety. On the firft glafs may be painted the palace. On the fecond, a view of 2 Plate the back part of the palace, with the altar. On the third, Priam with feveral Trojan men and women. On CLXII. the fourth, Pyrrhus and a troop of Greeks. On the fifth, the fame actors, with the palace in flames. On the fixth, a conflagration.-The two firft glaffes which are to be drawn up, fhould be placed before you raise the curtain. Then pass the third; next advance the fourth; which being drawn up, difcovers on the fifth the palace in flames; then drawing up the fixth, let down the first, that the palace may appear entirely deftroyed by the conflagration. The fourth act may reprefent the environs of Troy, with a diftant profpect of the fea. The first and third glaffes of the first act may be here ufed; to which may be added a third, representing Æneas bearing his father Anchifes, followed by his fon Iulus and fome Trojans. With this glafs may be reprefented the flight of the Trojans and the embarkment of Eneas; with another glass, on which are painted certain veffels.— To this act the following fcenes may be added: The cave of Æolus; the back part of the cave; Æolus; the winds; Juno in her chariot. The fifth act fhould reprefent the open fea, with the fleet of Æneas failing for Italy. On the firft glafs must be painted the fea, as in the eleventh Experiment, or elfe the waves fhould be imitated by another glass under the first. On the fecond, the Trojan fleet. On the third, Neptune in his car. On the fourth, the palace of Jupiter. On the fifth, the infide of the palace; the gods affembled in council, with Venus obtaining leave of Jupiter for Æneas to land in Italy.-After having placed the first glafs, that reprefents a calm fea, the curtain is raifed, and the fecond fcene is advanced, which contains the Trojan fleet. The firft is then brought forward, to reprefent a violent tempeft: then raifing the third glafs, Neptune appears, who commands the waves to be ftill, which is done by making the tempeft fubfide by degrees. The fleet then advances, and paffes over the whole theatre: prefently after the fourth and fifth fcenes defcend, that reprefent Olympus, and finish the exhibition. Note, We must here repeat, that if you would reprefent a fubject of this fort to advantage, it is quite neceffary that the glaffes be well painted; and those that are to be in front fhould be in ftronger and more opaque colours, that the images of those behind may not appear mixed with them, which will be the cafe if they are all equally tranfparent. The glaffes fhould alfo be of different lengths; that fome being placed before the others are drawn away, their extremities may not be perceived. The larger thefe fubjects are reprefented, the better effect they will have: the front of the theatre should appear to be about three feet wide; and if fome parts of the figures were moveable, it would still add to the variety of the entertainment. (G) He that moves the glaffes, feeing the effect they produce, is the better able to render the reprefentation as natural as poffible. N° 101. DIOSCOREA, Diofcorea height of five or fix feet: the stalks are of a fine coral Diopolis DIOSCOREA, in botany: A genus of the hexandria order, belonging to the diocia clafs of plants; and Diofma. in the natural method ranking under the 11th order, Sarmentacea. The male calyx is fexpartite; there is no corolla: The female calyx is fexpartite; no corolla; three ftyles; the capfule trilocular and compreffed; and there are two membranaceous feeds. There are eight fpecies, of which the only remarkable one is the bulbifera, or yam. This hath triangular winged ftalks, which trail upon the ground, and extend a great way: thefe frequently put out roots from their joints as they lie upon the ground, by which the plants are multiplied. The roots are eaten by the inhabitants of both the Indies; and are particularly ferviceable in the Weft India islands, where they make the great eft part of the negroes food. The plant is fuppofed to have been brought from the Eaft to the Weft Indies; for it has never been obferved to grow wild in any part of America; but in the island of Ceylon, and on the coaft of Malabar, it grows in the woods, and there are in thofe places a great variety of forts. It is propagated by cutting the root in pieces, obferving to preferve an eye in each, as is practifed in planting potatoes. One plant will produce three or four large roots. The fkin of these roots is pretty thick, rough, unequal, covered with many ftringy fibres or filaments, and of a violet colour approaching to black. The infide is white, and of the confiftence of red beet. It refembles the potato in its mealinefs, but is of a closer texture. When raw, the yams are vifcous and clammy: when roafted or boiled, they afford very nourishing food; and are of ten preferred to bread by the inhabitants of the Weft Indies, on account of their lightnefs and facility of digeftion. When firit dug out of the ground, the roots are placed in the fun to dry: after which, they are either put into fand, dry garrets, or cafks; where, if kept from moisture, they may be preferved whole years, without being fpoiled or diminished in their goodnefs. The root commonly weighs two or three pounds; tho' fome yams have been found upwards of 20 pounds weight. DIOSCORIDES, a phyfician of Cilicia, who lived, as fome fuppofe, in the age of Nero. He was originally a foldier; but afterwards he applied himfelf to ftudy, and wrote a book upon medicinal herbs. DIOSCURIA (Socip, from Ans Jupiter, and expo infants), in antiquity, a fettival in honour of the Aeneva, or Caftor and Pollux, who were reputed to be the fons of Jupiter. It was obferved by the Cyreneans, but more especially by the Spartans, whofe country was honoured by the birth of thefe heroes. The folemnity was full of mirth, being a time wherein they fhared plentifully of the gifts of Bacchus, and diverted themselves with fports, of which wrettling matches always made a part. DIOSMA, AFRICAN SPIRA: A genus of the monogynia order, belonging to the pentandria clafs of plants; and in the natural method ranking with thofe of which the order is doubtful. The corolla is pentapetalous, the nectarium crown-fhaped above the germen; there are five capfules coalited; the feeds hooded. There are nine fpccies; of which the moft remarkable are the hirfuta, with narrow hairy leaves; and the oppofitifolia, with leaves placed in the form of a crofs. The first is a very handfome fhrub, growing to the VOL. VI. Part I. DIOSPOLIS (anc. geog.), a city of the Delta, or Lower Egypt; to the fouth of the Bufiritic branch, before it divides into two.-Another of Bithynia, in the territory of Heraclea.-A third, called Magna, denoting Thebe of the Higher Egypt.-A fourth, Diof polis Parva, the metropolis of the Nomos Diofpolites of the Higher Egypt.-A fifth, Diofpolis of Samaria, the fame with Lydda.-A fixth Diofpolis, the ancient name of Laodicea of Phrygia on the Lycus. DIOSPOLITES NOMOS (Ptolemy), a divifion of Thebais or the Higher Egypt, to diftinguish it from another of the Lower Egypt or the Delta; to the fouth of the Nomos Thinites, on the weft fide of the Nile. DIOSPYROS, the INDIAN DATE-PLUM: A genus of the diocia order, belonging to the polygamia class of plants; and in the natural method ranking under the 18th order, Bicornes. The calyx is hermaphrodite and quadritid; the corolla urceolated and quadrifid; there are eight ftamina; the ftyle quadrifid; the berry octofpermous: the male calyx, corolla, and ftamina, as in the former. There are two fpecies. 1. The lotus, which is fuppofed to be a native of Africa, from whence it was tranfplanted into feveral parts of Italy, and alfo into the fouth of France. The fruit of this tree is fuppofed to be the lotus with which Ulyffes and his companions were enchanted, and which made those who eat of it forget their country and relations: (See alfo RHAMNUS.) In the warm parts of Europe this tree grows to the height of 30 feet. In the botanic garden at Padua, there is one very old tree which has been defcribed by fome of the former botanifts under the title of guaiacum patavinum. This tree produces plenty of fruit every year; from the feeds of which many plants have been raised. 2. The Virginiana, pinfhamin, perfimon, or pitchumon plum, is a native of America, but particularly of Virginia and Carolina. The feeds of this fort have been frequently imported into Britain, and the trees are common in many nurferies about London. It rifes to the height of 12 or 14 feet; but generally divides into many irregular F trunks # tics. in this country. Diphthong trunks near the ground, fo that it is very rare to fee a handsome tree of this fort. Though plenty of fruit is Diploma- produced on these trees, it never comes to perfection In America the inhabitants preferve the fruit till it is rotten, as is practifed with medlars in England; when they are efteemed very pleafant. Both species are propagated by feeds: and the plants require to be treated tenderly while young; but when they are grown up, they refift the greatest cold of this country. DIPHTHONG, in grammar, a double vowel, or the mixture of two vowels pronounced together, fo as to make one fyllable. The Latins pronounced the two vowels in their diph- English diphthongs, with regard to the eye and ear, DIPLOE, in anatomy, the foft meditullium, or DIPLOMA. See DIPLOMATICS. In a peculiar fense, it is used for an inftrument or licence given by colleges, focieties, &c. to a clergyman to exercise the minifterial function, or to a phyfician to practise the profeffion, &c. after paffing examination, or admitting him to a degree. DIPLOMATICS, the fcience of diplomas, or of Bielfield's Elements. ancient literary monuments, public documents, &c. It does not however, nor can it, abfolutely extend its refearches to antiquity; but is chiefly confined to the middle age, and the firft centuries of modern times. For though the ancients were accustomed to reduce their contracts and treaties into writing; yet they graved them on tables, or covered them over with wax, or brafs, copper, ftone, or wood, &c. And all that in the first ages were not traced on brass or marble, has perished by the length of time, and the number of deAructive events. tics. &c. The originals of thefe pieces are named Exam- Diploma- 1. The word diploma fignifies, properly, a letter or epiftle, that is folded in the middle, and that is not open. But, in more modern times, the title has been given to all ancient epiftles, letters, literary monuments, and public documents, and to all thofe pieces of writing which the ancients called Syngrapha, Chirographa, Codicilli, &c. In the middle age,, and in the diplomas themselves, thefe writings are called Littera, Precepta, Placita, Charte indicula, Sagilla, and Bulle; as alío Pancharta, Pantocharte, Tra&toria, Defcriptiones, 2. In order to understand the nature of these ancient papers, diplomas, and manufcripts, and to diftinguish 3. We are ignorant of the precife time when our guifhes the original from the counterfeit is, the writing 6 The one nicon tics. Diploma nicon Gotvicenfe. We there find specimens of all the characters, the flourishes, and different methods of writing, of every age. For thefe matters, therefore, we muft refer our readers to thofe authors; and fhall here only add, that, 4. All the diplomas are wrote in Latin, and confequently the letters and characters have a refemblance to each other: but there are certain ftrokes of the pen, which diftinguish not only the ages, but alfo the different nations; as the writings of the Lombards, French, Saxon, &c. The letters in the diplomas are also usually longer, and not fo ftrong as thofe of manufcripts. There has been also introduced a kind of court-hand, of a very disproportionate length, and the letters of which are called Exiles litteræ, crispæ, ac protractiores. The first line of the diploma, the fignature of the fovereign, that of the chancellor, notary, &c. are ufually wrote in this character. 5. The fignature of a diploma confits either of the fign of the crofs, or of a monogram or cipher, compofed of the letters of the names of those who fubfcribed it. The initial letters of the name, and fometimes alfo the titles, were placed about this cross. By degrees the custom changed, and they invented other marks; as, for example, the fign of Charlemagne was thus: They fometimes added alfo the dates and epoch of the fignature, the feafts of the church, the days of the kalendar, and other like matters. The fucceffive corruption of the Latin language, the ftyle and orthography of each age, as well as their different titles and forms; the abbreviations, accentuation, and punctuation, and the various methods of writing the diphthongs; all these matters united, form fo many characters and marks by which the authenticity of a diploma is to be known. 6. The feal annexed to a diploma was anciently of white wax, and artfully imprinted on the parchment itself. It was afterward pendent from the paper, and inclosed in a box or cafe, which they called bulla. There are fome also that are stamped on metal, and even on pure gold. When a diploma bears all the characters that are requifite to the time and place where it is fuppofed to be written, its authenticity is not to be doubted: but, at the fame time, we cannot examine them too fcrupulously, feeing that the monks and priests of former ages have been very adroit in making of counterfeits; and the more, as they enjoyed the confidence of princes and ftatefmen, and were even fometimes in poffeffion of their rings or feals. 7. With regard to manufcripts that were wrote before the invention of printing, it is neceffary (1.), to know their nature, their effential qualities, and matter; (2.) to be able to read them freely, and without error; (3.) to judge of their antiquity by thofe characters which we have juft mentioned with regard to the diplomas; and, (4.) to render them of use in the fciences. As there are scarce any of the ancient codes now remaining (fee par. 2.), wrote on the Egyptian paper, or on wood, ivory, &c. we have only to confider thofe that are written on parchment or vellum (membraneos), and fuch as are wrote on our paper (chartaceos). The Diploma former of these are in moft elteem. With regard to tics the character, these codes are written either in square and capital letters, or in half square, or round and Imall Dipping. letters. Thofe of the first kind are the most ancient. There are no intervals between the words, no letters different from the others at the beginning of any word, no points, nor any other diftinction. The codes which are wrote in letters that are half square, resemble those we have in Gothic characters, as well for the age as the form of the letters. Such as are wrote in round letters are not fo ancient as the former, and do not go higher than the ninth or tenth century. These have fpaces between the words, and fome punctuation. They are likewife not fo well wrote as the preceding, and are frequently disfigured with comments. The codes are divided, according to the country, into Lombard, Italian, Gaulic, Franco-Gaulic, Saxon, Anglo-Saxon, &c. 8. In the ancient Greek books, they frequently terminated the periods of a difcourfe, inftead of all other divifion, by lines; and these divifions were called, in Latin, verfus, from vertendo: for which reafon these lines are ftill more properly named verfus than lineæ. At the end of a work, they put down the number of verfes of which it confifted, that the copies might be more eafily collated: and it is in this fenfe we are to underftand Trebonius, when he fays, that the pandects contain 150,000 pane verfuum. These codes were likewife vel proba vel deterioris nota, more or lefs perfect not only with regard to the calligraphy or beauty of the character, but to the correction of the text alfo. 9. It is likewife neceffary to observe, in ancient codes, the abbreviations, as they have been used in different centuries. Thus, for example, A. C. D. fignifies, Aulus Caius Decimus; Ap. Cn. Appius Cneius; Aug. Imp. Auguftus Imperator. The characters that are called nota, are fuch as are not to be found in the alphabet; but which, notwithstanding, fignify certain words. All these matters are explained in a copious manner by Voffius, and in the Chronicon Gotvicenfe. Laftly, the learned divide all the ancient codes into codices minus raros, rariores, editos, & anecdotos. The critical art is here indifpenfably neceffary: its refearches, moreover, have no bounds; and the more, as the use of it augments every day, by the difcoveries that are made in languages, and by the increase of erudition. DIPONDIUS, in the fcripture-language, is used by St Luke to fignify a certain coin which was of very little value. Our tranflation of the paffage is, Are not two Sparrows fold for two farthings? In St Matthew, who relates the fame thing, we read Are not two parrows fold for a farthing? The Greek reads affarion inftead of as. Now affarion, as fome fay, was worth half an as, that is to fay, four French deniers and th; and, according to others, two deniers andths. Dipondius feems rather to fignify half an as. Calmet, Diction. Bibl. Luke xii. 6. Matt. x. 29. Dr Arbuthnot differs in opinion from the author laft quoted. He says,' that this coin was at first libralis, or of a pound weight; and even when diminished, it retained the name of libella. So that dipondius denotes two affes. DIPPING, among miners, fignifies the interruption F 2 Needle. juft over the middle of the large one, it will turn itself Dippingin fuch a manner that the fouth pole of the small magnet will point towards the north pole of the large one; and if at an equal diftance from both, will remain in an horizontal pofition. But if we move it nearer to one of the poles than the other, it will readily be underflood that the correfponding end of the needle will be attracted by the pole to which it approaches, and of confequence inclined downwards; the contrary end being proportionably elevated. It is likewife evident, that this inclination will be greater or lefs according to the distance at which the small magnet is placed from the pole of the large one; the attraction of the nearest pole having always the greatest effect upon it. And it is equally plain, that when brought directly over one of the poles of the large magnet, it will turn its own contrary one directly towards it, and thus lie exactly in the axis of the large one. Dipping- tion or breaking off the veins of ore; an accident that Needle. gives them a great deal of trouble before they can difcover the ore again. A great deal of the fkill of the miners confifts in the understanding this dipping of the veins, and knowing how to manage in it. In Corn wall they have this general rule to guide them in this refpect: most of their tin-loads, which run from ealt to weft, conftantly dip towards the north. Sometimes they underlie; that is, they flope down towards the north three feet in height perpendicular. This muft carefully be obferved by the miners, that they may exactly know where to make their air-fhafts when occafion requires; yet, in the higher mountains of Dartmaer, there are fome confiderable loads, which run north and fouth; thefe always underlie toward the eaft. Four or five loads may run nearly parallel to each other in the fame hill; and yet, which is rare, they may meet all together in one hatch, as it were a knot, which well tins the place, and fo feparate again, and keep their former distances. DIPPING-Needle, an inftrument ufed for obferving the quantity of inclination towards the earth, affumed by any needle or other body after it has acquired the magnetic virtue. This was firft obferved by one Robert Norman, an Englishman, and maker of compaffes for mariners, in the end of the 16th century; who finding that he was always obliged to counterbalance that end which turns to the north by a bit of wax or fuch other fubftance, though the balance had been ever fo exact before, publifhed an account of his difcovery as a matter of importance. The fubject was instantly attended to; and inftruments were not only contrived for afcertaining the quantity of the dip, but various fpeculations formed concerning the caufe of fuch a furprising phenomenon. The general phenomena of the dipping-needle are: That about the equatorial parts of the earth it remains in an horizontal pofition, but depreffes one end as we recede from thefe; the north end if we go towards the north, and the fouth end if we proceed towards the fouth pole. The farther north or fouth that we go, the inclination becomes the greater; but there is no place of the globe hitherto difcovered where it points directly downwards, though it is fuppofed that it would do fo in fome part very near the pole. Its inelination is likewife found to vary very confiderably at different times in different places of the earth, and by fome changes of fituation in fuch a manner as muft appear at first fight very unaccountable. Of all thofe who have attempted the investigation of this obfcure subject, none have been more fuccefsful than M. Cavallo, who in his Treatife on Magnetifm has given particular attention to all the phenomena, and accounted for them upon plain and rational principles, in the following manner. The dip of the magnetical needle in general may be understood from the following eafy experiment: Lay an oblong magnet horizontally upon a table, and over it fufpend another smaller magnet (a fewing needle to which the magnetic virtue has been communicated will anfwer the purpose), in fuch a manner as to remain in an horizontal pofition when not disturbed by another magnet. Now, if this laft fmall magnet or fewing needle, fufpended by the middle, be brought The application of this experiment to the phenomena of the dipping-needle is obvious, as nothing more is requifite for folving the whole mystery than to fuppofe the earth itfelf to be the large magnet, and the magnetic needle or any other magnetic body the fmall magnet in the experiment: for admitting that the northpole of the earth poffeffes a fouth magnetifm, and that the oppofite pole is poffeffed of a north magnetical polarity; it appears, and the theory is confirmed by experiment, that when a magnet is fufpended properly in the equatorial parts of the world, it must remain in an horizontal pofition; but when removed nearer to one of the poles, it must incline one of its extremities, viz. that which is poffeffed of the contrary magnetic polarity; and that this inclination must increase in proportion as the magnet or magnetic-needle recedes from the equator of the earth; and, laftly, when brought exactly upon either of the poles of the earth, it must ftand perpendicular to the ground, or in the fame direction with the axis of the earth. The only difficulty in this explanation arifes from. the attributing a fouth magnetifm to the north pole of the earth; but by this our author means only that its magnctifm is contrary to that end of the magnetic needle which turns towards it; and in the fame manner it must be understood, that the fouth pole of the earth has a north magnetic polarity. If the extremities of the axis of the earth, or the poles about which it performs its diurnal revolution, coincided with its magnetic poles, or even if the magnetic poles were always at a certain distance from them, the inclination of the needle would be always the fame at equal diftances from the equator, and might be very ufeful for determining the latitudes. But it would feem, that thefe poles are perpetually fhifting their place, fince both the inclination and horizontal direction of the needle are continually varying even in the fame place; fo that its quantity of inclination cannot be exactly calculated. Two general remarks may be made upon this fubject. 1. That the inclination of the needle does not alter regularly in going from north to fouth, or from fouth to north, in any meridian. 2. That its alteration in the fame place, and at different times, is but finall. Thus, in London, about the year 1576, the dip was 71° 50' below the horizon, and. in 1775 it stood at 72° 3'; the alteration in near 200 years. |