Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/598

 D I A

D I A

Mefon Tetrachord

Met — —

Lichanos Mefon — — G

Parypate Mefon 'Hypate Mefon

Hypaton Tetrachord S Lichanos Hypaton

Parypate Hypaton .Hypate Hypaton ■

_ — D

. — C BtJ

Proflambanomenos — — A

It is to be obferved, that this Diagram only reprefents the diatonic genus ; and therefore, after the names Lychanos Hypa- ton, and Lychanos Mefon, fome add Diatoms, to dittinguifh them from the Lichanoi of the Chromatic or harmonic genera. XVallis, Append, ad Ptolem. Harm. p. 157. See Lichanus. The Tetrachords in this Diagram are conjunct or disjunct. The conjunct have a common note, chord, or found. Thus the Hypate Mefon, which is the laft of the Hypaton Tetra- chord, is the firft of the mefon. The mefe alfo is the laft chord of the mefon, and the firft of the fynemmenon tetra- chord. So likewife the nete diezeugmenon is the laft chord of the diezeugmenon, and the firft of the hyperbolseon tetra- chord. The disjunct: tetrachords are thofe which are fepa- rated by a tone. Thus the mefon and diezeugmenon tetra- chords are feparated by the tone between the mefe and para- mefe : fo likewife the fynemmenon and hyperbolaeon tetrachords are feparated by the tone between the nete fynemmenon, and the nete diezeugmenon.

Some of the names of the chords in this Diagram being placed nearer to each other than the reft, fignify that there is only a femi-tone between them. Thus, between the hypate hypa- ton and the parypate hypaton, or between the mefe and the trite fynemmenon, or between the paramefe and trite die- zeugmenon, the interval is no more than a femi-tone. It has been obferved by Dr. Pepufch % that the antients con- fidered a defcending as well as an afcending fcale ; the former proceeding from acute to grave prectfely by the fame intervals, as the latter did from grave to acute, and the fame names fer- ved for both. But the proflambanomenos, and the reft of the names correfponded to different notes of our fcale. An ex- ample of one octave will explain the learned Author's meaning.

Afcending

A — • Proflambanomenos

B — Hypate hypaton C — Parypate hypaton

Defcending

_ _ f

D —, Lychanos hypaton — — d

E — Hypate mefon — — c

F — Parypate mefon — — b

G - — Lychanos mefon — — a

a — Mefe — — G

The intervals here, both afcending and defcending, are the fame, and in the fame order, viz. tone, femi-tone, tone, tone, femi-tone, tone, tone. So that the one fcale is pre- cifely the reverfe of the other. This diftinction of an afcend- ing and a defcending fcale, is faid to be conducive to the va- riety and perfection of melody, though little underftood by modern comporers. 1 * ['Phil. Tranf. N$ 481. p. 369. "Phil. Tranf. ibid.]

The eighteen names of the fcale of the antients do not feem to fignify fo many diftinct founds, efpecially in the diatonic genus, where the paranete fynemmenon and the trite die- zeugmenon, as alfo the nete fynemmenon and the paranete diezeugmenon, are reputed to coincide. Nor do the eighteen chords feem perfectly diftinct in any of the other genera, ex- cept in the enharmonic. IVallis's Append, ad Ptolem. Harm, p. 158. See Enharmonic.

DIAION, in the antient writers of medicine, the name of a compofition made into the form of troches, of which violet flowers were one of the principal ingredients. The compo- fition is defcribed at large by Myrepfuus.

DIAL-P/flKt'j", plain fuperficies, upon which the hour lines of dials are drawn. See Dial, Cycl.

D1ALITHA, in the writings of the antients, a word ufed to exprefs the elegant ornaments of the Greeks and Romans, compofed of gold and gemms. They alio called thefe Litho-

colla, cemented ftones or gemms: the gold being, j n ^ cafe, as a cement, to hold the ftones together. They wore bracelets and other ornamental things about their habits thus made; and their cups and table-furniture for magnificient treats were of this kind. The green ftones were found to fucceed beft of all in thefe things ; and the emerald and greenifh topaz or, as we call it, chryfolite, were molt in efteem for this purpofe. This ufe of the ftones explains what Pliny very of- ten fays of them in his defcription : Nihil juamd'tus aurum de- cet ; nothing becomes gold better: this, he fays, ofthegre eil topaz or chryfolite; and this, and many other like pauses have greatly perplexed the critics who did not hit upon this explication. The Latins called thefe Dialitha and Lkhocolla aurum gemmatum -, and thus Martial, where he fays miratur fcytbicas virentis auri flammas Jupiter, alludes to cups of Gold, ornamented with Scythian gemms, that is, emeralds. Some of the Latins have exprefTed thefe cups by the word Gemmium; but erroneoufly : for Gemmium is properly the name of a rofe or cup, formed out of fome one ftone, as an agate, or the like ; but the Gemmatum Pocculum is not a cup made of a gemm, but befet with gemms : this therefore is properly the Dialithum of the Greeks.

DIALLACTERII, among the Athenians. See Dijetetje.

DIALLELOS, A/«mha.©-, in rhetoric, a figure, wherein the words and meaning of a fentence are inverted, as doftis difcr- tior, dijertis doRior. Vojf. Rhet. 1. 5. p. 405.

DIALLING (Cycl.) — The general theory of Dialling is eafily deduced from the principles of the fphere, and thofe of per- fpe£tive. The moft fimple kind of Dial is the equinoctial, where the lhadow is received upon a plane parallel to the cir- cles of the fun's diurnal motion, or to the equator ; and is projected by a ftile, or right line perpendicular to thofe planes. As the fun moves over equal arcs on its parallel in equal times ; the motion of the fhadow in this Dial muft likewife be uni- form, fo that the intervals between the hours muft be equal, which is done by dividing a circle into twenty-four equal parts. The conftruction of other Dials may be deduced from this, by the rules of perfpective. For one Dial may be confi- dered as the projection of another, on a propofed plane. Practical Rules for the conftruction of Dials, are given in the Cyclopedia under Dial. Thofe who defire farther inftruc- tions may confult the authors there mentioned in the article Dialling.

A horizontal Dial being given, others may be defcribed from it, in the manner fhewn by s'Gravefande, in his efiay on perfpective, chap. 9.

DIALOGISM, Aw^ojfrj^©', in rhetoric, is ufed for the folilo- quy of perfons deliberating with themfelves. We have an in- ftance of it in Virgil, where Dido fays,

En quid agam ? rurfufne procos irrija prior es Experiar ? &c.

In which fenfe it is diftingtiiihcd from dialogue. Vojf. Rhet. I.5. p. 355. See Dialogue, Cycl.

Dialogism is alfo taken in a more extenfive fenfe for difcourfe in general, whether held by a perfon alone, or in company. Vojf. loc. cit.

DIAMARTYRIA, &iana.?Tv<>i*., in antiquity, a proteftation that the deceafed perfon had left an heir ; and made to hinder the relations from entering upon the eftate. Pott. Archasol. Grate. 1. 1. c. 24. T. 1. p. 128.

DIAMNES, a word ufed by Johannes Anglicus, and fome other authors, for an involuntary difcharge of urine.

DIAMOND [Cycl.) — Specific gravity of Diamonds. Mr. Boyle has given us the obfervation of a peribn much converfant in Diamonds, that fome of thofe gemms in their rough ftate were much heavier than others of the fame bignefs, efpecially if they were cloudy or foul ; and Mr. Boyle mentions one that weighed 8 grains and ~r> which being carefully weigh'd in water, according to the rules of hydroftatics, proved to an equal bulk of that liquor, as 2 §<§■ to 1. So that as far as could be judged by that experiment, a Diamond weighs not thrice fo much as water ; and yet in his table of fpecific gravities, that of a Dia?nond is faid to be to water as 3400 to 1000, that is, as 3 J to 1 ; and therefore, according to thefe two accounts, there fhould be fome Diamonds whole fpecific gravity differs nearly ^ from that of others. But this is a much greater dif- ference than can be expected in two bodies of the fame fpecies, and indeed on an accurate trial does not prove to be the cafe in Diamonds. The Bralil Diamonds differ a little in weight one from another, and greatly vary from the ftandard fet by Mr. Boyle for the fpecific gravity of this gem in general; two large Diamonds of that part of the world being carefully weigh- ed, one was found as 3518, and the other as 3521 to 1000, to an equal bulk of water. Each of thefe therefore greatly exceeded the heavieir. of Mr, Boyle's in fpecific gravity, and the difference between them was lefs than one thoufandth part. Two fmaller Brazil Diamonds bzing afterwards weighed, proved not to be quite fo heavy as thefe, the lighted: being as 3501* and the heavieft as 3511 to 1000, in proportion to an equal bulk of water. Atter this ten Eaft India Diamonds were cho-

fen